Dissociating the nicotine and airway sensory effects of smoking

Electronic cigarettes for smoking cessation

BACKGROUND

Electronic cigarettes (ECs) are handheld electronic vaping devices that produce an aerosol by heating an e-liquid. People who smoke, healthcare providers, and regulators want to know if ECs can help people quit smoking, and if they are safe to use for this purpose. This is a review update conducted as part of a living systematic review.

OBJECTIVES

To examine the safety, tolerability, and effectiveness of using EC to help people who smoke tobacco achieve long-term smoking abstinence, in comparison to non-nicotine EC, other smoking cessation treatments, and no treatment.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, and PsycINFO to 1 February 2024 and the Cochrane Tobacco Addiction Group's Specialized Register to 1 February 2023, reference-checked, and contacted study authors.

SELECTION CRITERIA

We included trials randomizing people who smoke to an EC or control condition. We included uncontrolled intervention studies in which all participants received an EC intervention. Studies had to report an eligible outcome.

DATA COLLECTION AND ANALYSIS

We followed standard Cochrane methods for screening and data extraction. We used the risk of bias tool (RoB 1) and GRADE to assess the certainty of evidence. Critical outcomes were abstinence from smoking after at least six months, adverse events (AEs), and serious adverse events (SAEs). Important outcomes were biomarkers, toxicants/carcinogens, and longer-term EC use. We used a fixed-effect Mantel-Haenszel model to calculate risk ratios (RRs) with a 95% confidence interval (CI) for dichotomous outcomes. For continuous outcomes, we calculated mean differences. Where appropriate, we pooled data in pairwise and network meta-analyses (NMA).

MAIN RESULTS

We included 90 completed studies (two new to this update), representing 29,044 participants, of which 49 were randomized controlled trials (RCTs). Of the included studies, we rated 10 (all but one contributing to our main comparisons) at low risk of bias overall, 61 at high risk overall (including all non-randomized studies), and the remainder at unclear risk. Nicotine EC results in increased quit rates compared to nicotine replacement therapy (NRT) (high-certainty evidence) (RR 1.59, 95% CI 1.30 to 1.93; I2 = 0%; 7 studies, 2544 participants). In absolute terms, this might translate to an additional four quitters per 100 (95% CI 2 to 6 more). The rate of occurrence of AEs is probably similar between groups (moderate-certainty evidence (limited by imprecision)) (RR 1.03, 95% CI 0.91 to 1.17; I2 = 0%; 5 studies, 2052 participants). SAEs were rare, and there is insufficient evidence to determine whether rates differ between groups due to very serious imprecision (RR 1.20, 95% CI 0.90 to 1.60; I2 = 32%; 6 studies, 2761 participants; low-certainty evidence). Nicotine EC probably results in increased quit rates compared to non-nicotine EC (moderate-certainty evidence, limited by imprecision) (RR 1.46, 95% CI 1.09 to 1.96; I2 = 4%; 6 studies, 1613 participants). In absolute terms, this might lead to an additional three quitters per 100 (95% CI 1 to 7 more). There is probably little to no difference in the rate of AEs between these groups (moderate-certainty evidence) (RR 1.01, 95% CI 0.91 to 1.11; I2 = 0%; 5 studies, 840 participants). There is insufficient evidence to determine whether rates of SAEs differ between groups, due to very serious imprecision (RR 1.00, 95% CI 0.56 to 1.79; I2 = 0%; 9 studies, 1412 participants; low-certainty evidence). Compared to behavioural support only/no support, quit rates may be higher for participants randomized to nicotine EC (low-certainty evidence due to issues with risk of bias) (RR 1.96, 95% CI 1.66 to 2.32; I2 = 0%; 11 studies, 6819 participants). In absolute terms, this represents an additional four quitters per 100 (95% CI 3 to 5 more). There was some evidence that (non-serious) AEs may be more common in people randomized to nicotine EC (RR 1.18, 95% CI 1.10 to 1.27; I2 = 6%; low-certainty evidence; 6 studies, 2351 participants) and, again, insufficient evidence to determine whether rates of SAEs differed between groups (RR 0.93, 95% CI 0.68 to 1.28; I2 = 0%; 12 studies, 4561 participants; very low-certainty evidence). Results from the NMA were consistent with those from pairwise meta-analyses for all critical outcomes. There was inconsistency in the AE network, which was explained by a single outlying study contributing the only direct evidence for one of the nodes. Data from non-randomized studies were consistent with RCT data. The most commonly reported AEs were throat/mouth irritation, headache, cough, and nausea, which tended to dissipate with continued EC use. Very few studies reported data on other outcomes or comparisons; hence, evidence for these is limited, with CIs often encompassing both clinically significant harm and benefit.

AUTHORS' CONCLUSIONS

There is high-certainty evidence that ECs with nicotine increase quit rates compared to NRT and moderate-certainty evidence that they increase quit rates compared to ECs without nicotine. Evidence comparing nicotine EC with usual care or no treatment also suggests benefit, but is less certain due to risk of bias inherent in the study design. Confidence intervals were, for the most part, wide for data on AEs, SAEs, and other safety markers, with no evidence for a difference in AEs between nicotine and non-nicotine ECs nor between nicotine ECs and NRT, but low-certainty evidence for increased AEs compared with behavioural support/no support. Overall incidence of SAEs was low across all study arms. We did not detect evidence of serious harm from nicotine EC, but longer, larger studies are needed to fully evaluate EC safety. Our included studies tested regulated nicotine-containing EC; illicit products and/or products containing other active substances (e.g. tetrahydrocannabinol (THC)) may have different harm profiles. The main limitation of the evidence base remains imprecision due to the small number of RCTs, often with low event rates. Further RCTs are underway. To ensure the review continues to provide up-to-date information to decision-makers, this is a living systematic review. We run searches monthly, with the review updated when relevant new evidence becomes available. Please refer to the Cochrane Database of Systematic Reviews for the review's current status.

Electronic cigarettes for smoking cessation

BACKGROUND

Electronic cigarettes (ECs) are handheld electronic vaping devices which produce an aerosol by heating an e-liquid. People who smoke, healthcare providers and regulators want to know if ECs can help people quit smoking, and if they are safe to use for this purpose. This is a review update conducted as part of a living systematic review.

OBJECTIVES

To examine the safety, tolerability and effectiveness of using electronic cigarettes (ECs) to help people who smoke tobacco achieve long-term smoking abstinence, in comparison to non-nicotine EC, other smoking cessation treatments and no treatment.

SEARCH METHODS

We searched the Cochrane Tobacco Addiction Group's Specialized Register to 1 February 2023, and Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, and PsycINFO to 1 July 2023, and reference-checked and contacted study authors.

SELECTION CRITERIA

We included trials in which people who smoke were randomized to an EC or control condition. We also included uncontrolled intervention studies in which all participants received an EC intervention as these studies have the potential to provide further information on harms and longer-term use. Studies had to report an eligible outcome.

DATA COLLECTION AND ANALYSIS

We followed standard Cochrane methods for screening and data extraction. Critical outcomes were abstinence from smoking after at least six months, adverse events (AEs), and serious adverse events (SAEs). We used a fixed-effect Mantel-Haenszel model to calculate risk ratios (RRs) with a 95% confidence interval (CI) for dichotomous outcomes. For continuous outcomes, we calculated mean differences. Where appropriate, we pooled data in pairwise and network meta-analyses (NMA).

MAIN RESULTS

We included 88 completed studies (10 new to this update), representing 27,235 participants, of which 47 were randomized controlled trials (RCTs). Of the included studies, we rated ten (all but one contributing to our main comparisons) at low risk of bias overall, 58 at high risk overall (including all non-randomized studies), and the remainder at unclear risk. There is high certainty that nicotine EC increases quit rates compared to nicotine replacement therapy (NRT) (RR 1.59, 95% CI 1.29 to 1.93; I2 = 0%; 7 studies, 2544 participants). In absolute terms, this might translate to an additional four quitters per 100 (95% CI 2 to 6 more). There is moderate-certainty evidence (limited by imprecision) that the rate of occurrence of AEs is similar between groups (RR 1.03, 95% CI 0.91 to 1.17; I2 = 0%; 5 studies, 2052 participants). SAEs were rare, and there is insufficient evidence to determine whether rates differ between groups due to very serious imprecision (RR 1.20, 95% CI 0.90 to 1.60; I2 = 32%; 6 studies, 2761 participants; low-certainty evidence). There is moderate-certainty evidence, limited by imprecision, that nicotine EC increases quit rates compared to non-nicotine EC (RR 1.46, 95% CI 1.09 to 1.96; I2 = 4%; 6 studies, 1613 participants). In absolute terms, this might lead to an additional three quitters per 100 (95% CI 1 to 7 more). There is moderate-certainty evidence of no difference in the rate of AEs between these groups (RR 1.01, 95% CI 0.91 to 1.11; I2 = 0%; 5 studies, 1840 participants). There is insufficient evidence to determine whether rates of SAEs differ between groups, due to very serious imprecision (RR 1.00, 95% CI 0.56 to 1.79; I2 = 0%; 9 studies, 1412 participants; low-certainty evidence). Due to issues with risk of bias, there is low-certainty evidence that, compared to behavioural support only/no support, quit rates may be higher for participants randomized to nicotine EC (RR 1.88, 95% CI 1.56 to 2.25; I2 = 0%; 9 studies, 5024 participants). In absolute terms, this represents an additional four quitters per 100 (95% CI 2 to 5 more). There was some evidence that (non-serious) AEs may be more common in people randomized to nicotine EC (RR 1.22, 95% CI 1.12 to 1.32; I2 = 41%, low-certainty evidence; 4 studies, 765 participants) and, again, insufficient evidence to determine whether rates of SAEs differed between groups (RR 0.89, 95% CI 0.59 to 1.34; I2 = 23%; 10 studies, 3263 participants; very low-certainty evidence). Results from the NMA were consistent with those from pairwise meta-analyses for all critical outcomes, and there was no indication of inconsistency within the networks. Data from non-randomized studies were consistent with RCT data. The most commonly reported AEs were throat/mouth irritation, headache, cough, and nausea, which tended to dissipate with continued EC use. Very few studies reported data on other outcomes or comparisons, hence, evidence for these is limited, with CIs often encompassing both clinically significant harm and benefit.

AUTHORS' CONCLUSIONS

There is high-certainty evidence that ECs with nicotine increase quit rates compared to NRT and moderate-certainty evidence that they increase quit rates compared to ECs without nicotine. Evidence comparing nicotine EC with usual care/no treatment also suggests benefit, but is less certain due to risk of bias inherent in the study design. Confidence intervals were for the most part wide for data on AEs, SAEs and other safety markers, with no difference in AEs between nicotine and non-nicotine ECs nor between nicotine ECs and NRT. Overall incidence of SAEs was low across all study arms. We did not detect evidence of serious harm from nicotine EC, but the longest follow-up was two years and the number of studies was small. The main limitation of the evidence base remains imprecision due to the small number of RCTs, often with low event rates. Further RCTs are underway. To ensure the review continues to provide up-to-date information to decision-makers, this review is a living systematic review. We run searches monthly, with the review updated when relevant new evidence becomes available. Please refer to the Cochrane Database of Systematic Reviews for the review's current status.

Black Pepper (Piper nigrum) for Tobacco Withdrawal: A Case Report

Tobacco use continues to be one of humanity’s most significant public health concerns, causing more than 8-million deaths annually. Existing treatments for tobacco use disorder are limited in efficacy and there is a strong need for identifying effective novel treatments. Small clinical trials indicate that black pepper (Piper nigrum) essential oil may be helpful for treating nicotine withdrawal and craving. However, we are unaware of any cases reporting the use of black pepper for these purposes in nonresearch settings. Here we present the case of a patient who inhaled combusted black pepper to self-medicate nicotine withdrawal when lacking access to tobacco cigarettes while incarcerated. Based on our patient’s report, inhalation of combusted black pepper may have alleviated his tobacco withdrawal and cravings by reducing his automatic motor urge to smoke, quelling withdrawal-associated anxiety, and mimicking the sensorimotor experience of smoking tobacco cigarettes. Notably, our patient reported that inhalation of combusted black pepper for treatment of nicotine craving and withdrawal was common in his correctional facility. Though combusted black pepper is highly unlikely to be an appealing treatment outside of a correctional setting, this case suggests that further investigation of vaporized black pepper essential oil for tobacco cessation may be warranted.

Impact of a reduced nicotine standard on young adult appeal for menthol and non-menthol cigarettes

INTRODUCTION

The Food and Drug Administration (FDA) announced its intention to reduce the nicotine content in cigarettes as a strategy to promote cessation and reduce smoking-related harm. A low nicotine product standard will apply to all cigarettes on the market, including menthol cigarettes. In December 2021, the FDA approved a modified risk tobacco product application for menthol and non-menthol flavoured very low nicotine cigarettes (VLNC) from the 22nd Century Group. Notably, experimentation with menthol cigarettes is linked to smoking progression, as well as greater nicotine dependence relative to non-menthol cigarette use. If menthol VLNCs are perceived as more appealing than non-menthol VLNCs, this would indicate that some aspect of menthol may maintain smoking even in the absence of nicotine and FDA's regulatory authority to ban or restrict the sale of menthol cigarettes should apply to reduced nicotine content of cigarettes. In April 2022, the FDA announced proposed rulemaking to prohibit menthol cigarettes, however it is unclear if a menthol prohibition would apply to VLNCs.

METHODS AND ANALYSIS

This study will recruit 172 young adult menthol smokers (with a specific subsample of n=40 sexual and gender minority young adults) and measure appeal for smoking experimental menthol and non-menthol VLNCs, and the impact of proposed product standards on tobacco product purchasing behaviour using an Experimental Tobacco Marketplace. Appeal across product standards will be assessed in a controlled laboratory and using ecological momentary assessment.

ETHICS AND DISSEMINATION

The protocol was approved by the University of Oklahoma Health Sciences Center Institutional Review Board (#11865). Findings will examine the effects of a reduced nicotine standard and a menthol ban on young adult smoking and will be disseminated through peer-reviewed journal articles and presentations at scientific conferences.

TRIAL REGISTRATION NUMBER

NCT04340947.

Electronic cigarettes for smoking cessation

BACKGROUND

Electronic cigarettes (ECs) are handheld electronic vaping devices which produce an aerosol by heating an e-liquid. Some people who smoke use ECs to stop or reduce smoking, although some organizations, advocacy groups and policymakers have discouraged this, citing lack of evidence of efficacy and safety. People who smoke, healthcare providers and regulators want to know if ECs can help people quit smoking, and if they are safe to use for this purpose. This is a review update conducted as part of a living systematic review.

OBJECTIVES

To examine the effectiveness, tolerability, and safety of using electronic cigarettes (ECs) to help people who smoke tobacco achieve long-term smoking abstinence.

SEARCH METHODS

We searched the Cochrane Tobacco Addiction Group's Specialized Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, and PsycINFO to 1 July 2022, and reference-checked and contacted study authors.  SELECTION CRITERIA: We included randomized controlled trials (RCTs) and randomized cross-over trials, in which people who smoke were randomized to an EC or control condition. We also included uncontrolled intervention studies in which all participants received an EC intervention. Studies had to report abstinence from cigarettes at six months or longer or data on safety markers at one week or longer, or both.

DATA COLLECTION AND ANALYSIS

We followed standard Cochrane methods for screening and data extraction. Our primary outcome measures were abstinence from smoking after at least six months follow-up, adverse events (AEs), and serious adverse events (SAEs). Secondary outcomes included the proportion of people still using study product (EC or pharmacotherapy) at six or more months after randomization or starting EC use, changes in carbon monoxide (CO), blood pressure (BP), heart rate, arterial oxygen saturation, lung function, and levels of carcinogens or toxicants, or both. We used a fixed-effect Mantel-Haenszel model to calculate risk ratios (RRs) with a 95% confidence interval (CI) for dichotomous outcomes. For continuous outcomes, we calculated mean differences. Where appropriate, we pooled data in meta-analyses.

MAIN RESULTS

We included 78 completed studies, representing 22,052 participants, of which 40 were RCTs. Seventeen of the 78 included studies were new to this review update. Of the included studies, we rated ten (all but one contributing to our main comparisons) at low risk of bias overall, 50 at high risk overall (including all non-randomized studies), and the remainder at unclear risk. There was high certainty that quit rates were higher in people randomized to nicotine EC than in those randomized to nicotine replacement therapy (NRT) (RR 1.63, 95% CI 1.30 to 2.04; I2 = 10%; 6 studies, 2378 participants). In absolute terms, this might translate to an additional four quitters per 100 (95% CI 2 to 6). There was moderate-certainty evidence (limited by imprecision) that the rate of occurrence of AEs was similar between groups (RR 1.02, 95% CI 0.88 to 1.19; I2 = 0%; 4 studies, 1702 participants). SAEs were rare, but there was insufficient evidence to determine whether rates differed between groups due to very serious imprecision (RR 1.12, 95% CI 0.82 to 1.52; I2 = 34%; 5 studies, 2411 participants). There was moderate-certainty evidence, limited by imprecision, that quit rates were higher in people randomized to nicotine EC than to non-nicotine EC (RR 1.94, 95% CI 1.21 to 3.13; I2 = 0%; 5 studies, 1447 participants). In absolute terms, this might lead to an additional seven quitters per 100 (95% CI 2 to 16). There was moderate-certainty evidence of no difference in the rate of AEs between these groups (RR 1.01, 95% CI 0.91 to 1.11; I2 = 0%; 5 studies, 1840 participants). There was insufficient evidence to determine whether rates of SAEs differed between groups, due to very serious imprecision (RR 1.00, 95% CI 0.56 to 1.79; I2 = 0%; 8 studies, 1272 participants). Compared to behavioural support only/no support, quit rates were higher for participants randomized to nicotine EC (RR 2.66, 95% CI 1.52 to 4.65; I2 = 0%; 7 studies, 3126 participants). In absolute terms, this represents an additional two quitters per 100 (95% CI 1 to 3). However, this finding was of very low certainty, due to issues with imprecision and risk of bias. There was some evidence that (non-serious) AEs were more common in people randomized to nicotine EC (RR 1.22, 95% CI 1.12 to 1.32; I2 = 41%, low certainty; 4 studies, 765 participants) and, again, insufficient evidence to determine whether rates of SAEs differed between groups (RR 1.03, 95% CI 0.54 to 1.97; I2 = 38%; 9 studies, 1993 participants).  Data from non-randomized studies were consistent with RCT data. The most commonly reported AEs were throat/mouth irritation, headache, cough, and nausea, which tended to dissipate with continued EC use. Very few studies reported data on other outcomes or comparisons, hence evidence for these is limited, with CIs often encompassing clinically significant harm and benefit.

AUTHORS' CONCLUSIONS

There is high-certainty evidence that ECs with nicotine increase quit rates compared to NRT and moderate-certainty evidence that they increase quit rates compared to ECs without nicotine. Evidence comparing nicotine EC with usual care/no treatment also suggests benefit, but is less certain. More studies are needed to confirm the effect size. Confidence intervals were for the most part wide for data on AEs, SAEs and other safety markers, with no difference in AEs between nicotine and non-nicotine ECs nor between nicotine ECs and NRT. Overall incidence of SAEs was low across all study arms. We did not detect evidence of serious harm from nicotine EC, but longest follow-up was two years and the number of studies was small. The main limitation of the evidence base remains imprecision due to the small number of RCTs, often with low event rates, but further RCTs are underway. To ensure the review continues to provide up-to-date information to decision-makers, this review is a living systematic review. We run searches monthly, with the review updated when relevant new evidence becomes available. Please refer to the Cochrane Database of Systematic Reviews for the review's current status.

Does genetic variation in a bitter taste receptor gene alter early smoking behaviours in adolescents and young adults?

BACKGROUND AND AIMS

Variation in the TAS2R38 taste receptor gene alters the ability to taste bitter compounds. We tested whether TAS2R38 variation influences early smoking behaviours in adolescence, a critical period of acquisition when taste may influence the natural course of tobacco use.

DESIGN AND PARTICIPANTS

Observational study (Nicotine Dependence in Teens [NDIT]). Cox proportional hazards models were conducted using data from European ancestry adolescent participants who initiated smoking during follow-up (n = 219, i.e. incident smokers). In young adulthood, cross-sectional analyses were restricted to European ancestry self-reported current smokers at age 24 (n = 148).

SETTING

Montréal, Canada.

MEASUREMENTS

In adolescents, the rates of attaining early smoking milestones were estimated for tasters {PAV diplotypes (i.e. PAV/PAV or PAV/AVI)} versus non-tasters {AVI diplotype (i.e. AVI/AVI)}. In young adults, associations between tasting status and a nicotine intake biomarker (cotinine + 3'hydroxycotinine) and past-week cigarette consumption were assessed.

FINDINGS

Among incident smokers, similar rates to first whole cigarette were found between the diplotype groups (hazard ratio [HR], 1.05; 95% confidence interval (CI), 0.75-1.48; P = 0.765). However, smokers with the PAV (vs AVI) diplotypes attained monthly smoking more rapidly (HR, 1.55; 95% CI, 1.04-2.32; P = 0.033) and had faster conversion to three different measures of tobacco dependence (International Classification of Diseases: HR, 2.29; 95% CI, 0.99-5.28; P = 0.052; modified Fagerström Tolerance Questionnaire: HR, 3.02, 95% CI, 1.04-8.79; P = 0.043; Hooked on Nicotine Checklist: HR, 1.87; 95% CI, 0.98-3.60; P = 0.059). At age 24, those with PAV (vs AVI) diplotypes had higher mean cotinine + 3'hydroxycotinine (197 vs 143 ng/mL; P = 0.053).

CONCLUSIONS

Adolescents with a genetic variation increasing their ability to taste bitter compounds appear to escalate more quickly to monthly smoking and tobacco dependence during adolescence and have higher nicotine intake in young adulthood versus those without that genetic variation.

A "Good" Smoke? The Off-Label Use of Cannabidiol to Reduce Cannabis Use

BACKGROUND

Although cannabis use is common in France, it is still criminalized. Cannabidiol (CBD) products, including CBD-rich cannabis, are legally available. Although previous results suggested that CBD may have benefits for people with cannabis use disorder, there is a lack of data on cannabis users who use CBD to reduce their cannabis consumption. We aimed to identify (i) correlates of this motive, and (ii) factors associated with successful attempts to reduce cannabis use.

METHODS

A cross-sectional online survey among French-speaking CBD and cannabis users was conducted. Logistic regressions were performed to identify correlates of using CBD to reduce cannabis consumption and correlates of reporting a large reduction.

RESULTS

Eleven percent (n = 105) of our study sample reported they primarily used CBD to reduce cannabis consumption. Associated factors included smoking tobacco cigarettes (adjusted odds ratio (aOR) [95% confidence interval (CI)] 2.17 [1.3-3.62], p = 0.003) and drinking alcohol (aOR [95%CI] 1.8 [1.02-3.18], p = 0.042). Of these 105, 83% used CBD-rich cannabis to smoke, and 58.7% reported a large reduction in cannabis consumption. This large reduction was associated with non-daily cannabis use (aOR [95%CI] 7.14 [2.4-20.0], p < 0.001) and daily CBD use (aOR [95%CI] 5.87 [2.09-16.47], p = 0.001). A reduction in cannabis withdrawal symptoms thanks to CBD use was the most-cited effect at play in self-observed cannabis reduction.

CONCLUSIONS

Cannabis use reduction is a reported motive for CBD use-especially CBD-rich cannabis to smoke-in France. More studies are needed to explore practices associated with this motive and to accurately assess CBD effectiveness.

Electronic cigarettes for smoking cessation

BACKGROUND

Electronic cigarettes (ECs) are handheld electronic vaping devices which produce an aerosol formed by heating an e-liquid. Some people who smoke use ECs to stop or reduce smoking, but some organizations, advocacy groups and policymakers have discouraged this, citing lack of evidence of efficacy and safety. People who smoke, healthcare providers and regulators want to know if ECs can help people quit and if they are safe to use for this purpose. This is an update conducted as part of a living systematic review.

OBJECTIVES

To examine the effectiveness, tolerability, and safety of using electronic cigarettes (ECs) to help people who smoke tobacco achieve long-term smoking abstinence.

SEARCH METHODS

We searched the Cochrane Tobacco Addiction Group's Specialized Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, and PsycINFO to 1 May 2021, and reference-checked and contacted study authors. We screened abstracts from the Society for Research on Nicotine and Tobacco (SRNT) 2021 Annual Meeting.   SELECTION CRITERIA: We included randomized controlled trials (RCTs) and randomized cross-over trials, in which people who smoke were randomized to an EC or control condition. We also included uncontrolled intervention studies in which all participants received an EC intervention. Studies had to report abstinence from cigarettes at six months or longer or data on safety markers at one week or longer, or both.

DATA COLLECTION AND ANALYSIS

We followed standard Cochrane methods for screening and data extraction. Our primary outcome measures were abstinence from smoking after at least six months follow-up, adverse events (AEs), and serious adverse events (SAEs). Secondary outcomes included the proportion of people still using study product (EC or pharmacotherapy) at six or more months after randomization or starting EC use, changes in carbon monoxide (CO), blood pressure (BP), heart rate, arterial oxygen saturation, lung function, and levels of carcinogens or toxicants or both. We used a fixed-effect Mantel-Haenszel model to calculate risk ratios (RRs) with a 95% confidence interval (CI) for dichotomous outcomes. For continuous outcomes, we calculated mean differences. Where appropriate, we pooled data in meta-analyses.

MAIN RESULTS

We included 61 completed studies, representing 16,759 participants, of which 34 were RCTs. Five of the 61 included studies were new to this review update. Of the included studies, we rated seven (all contributing to our main comparisons) at low risk of bias overall, 42 at high risk overall (including all non-randomized studies), and the remainder at unclear risk. There was moderate-certainty evidence, limited by imprecision, that quit rates were higher in people randomized to nicotine EC than in those randomized to nicotine replacement therapy (NRT) (risk ratio (RR) 1.53, 95% confidence interval (CI) 1.21 to 1.93; I2 = 0%; 4 studies, 1924 participants). In absolute terms, this might translate to an additional three quitters per 100 (95% CI 1 to 6). There was low-certainty evidence (limited by very serious imprecision) that the rate of occurrence of AEs was similar (RR 0.98, 95% CI 0.80 to 1.19; I2 = 0%; 2 studies, 485 participants). SAEs were rare, but there was insufficient evidence to determine whether rates differed between groups due to very serious imprecision (RR 1.30, 95% CI 0.89 to 1.90: I2 = 0; 4 studies, 1424 participants). There was moderate-certainty evidence, again limited by imprecision, that quit rates were higher in people randomized to nicotine EC than to non-nicotine EC (RR 1.94, 95% CI 1.21 to 3.13; I2 = 0%; 5 studies, 1447 participants). In absolute terms, this might lead to an additional seven quitters per 100 (95% CI 2 to 16). There was moderate-certainty evidence of no difference in the rate of AEs between these groups (RR 1.01, 95% CI 0.91 to 1.11; I2 = 0%; 3 studies, 601 participants). There was insufficient evidence to determine whether rates of SAEs differed between groups, due to very serious imprecision (RR 1.06, 95% CI 0.47 to 2.38; I2 = 0; 5 studies, 792 participants). Compared to behavioural support only/no support, quit rates were higher for participants randomized to nicotine EC (RR 2.61, 95% CI 1.44 to 4.74; I2 = 0%; 6 studies, 2886 participants). In absolute terms this represents an additional six quitters per 100 (95% CI 2 to 15). However, this finding was of very low certainty, due to issues with imprecision and risk of bias. There was some evidence that non-serious AEs were more common in people randomized to nicotine EC (RR 1.22, 95% CI 1.12 to 1.32; I2 = 41%, low certainty; 4 studies, 765 participants), and again, insufficient evidence to determine whether rates of SAEs differed between groups (RR 1.51, 95% CI 0.70 to 3.24; I2 = 0%; 7 studies, 1303 participants).  Data from non-randomized studies were consistent with RCT data. The most commonly reported AEs were throat/mouth irritation, headache, cough, and nausea, which tended to dissipate with continued use. Very few studies reported data on other outcomes or comparisons, hence evidence for these is limited, with CIs often encompassing clinically significant harm and benefit.

AUTHORS' CONCLUSIONS

There is moderate-certainty evidence that ECs with nicotine increase quit rates compared to NRT and compared to ECs without nicotine. Evidence comparing nicotine EC with usual care/no treatment also suggests benefit, but is less certain. More studies are needed to confirm the effect size. Confidence intervals were for the most part wide for data on AEs, SAEs and other safety markers, with no difference in AEs between nicotine and non-nicotine ECs. Overall incidence of SAEs was low across all study arms. We did not detect  evidence of harm from nicotine EC, but longest follow-up was two years and the  number of studies was small. The main limitation of the evidence base remains imprecision due to the small number of RCTs, often with low event rates, but further RCTs are underway. To ensure the review continues to provide up-to-date information to decision-makers, this review is now a living systematic review. We run searches monthly, with the review updated when relevant new evidence becomes available. Please refer to the Cochrane Database of Systematic Reviews for the review's current status.

Electronic cigarettes for smoking cessation

BACKGROUND

Electronic cigarettes (ECs) are handheld electronic vaping devices which produce an aerosol formed by heating an e-liquid. Some people who smoke use ECs to stop or reduce smoking, but some organizations, advocacy groups and policymakers have discouraged this, citing lack of evidence of efficacy and safety. People who smoke, healthcare providers and regulators want to know if ECs can help people quit and if they are safe to use for this purpose. This is an update of a review first published in 2014.

OBJECTIVES

To examine the effectiveness, tolerability, and safety of using electronic cigarettes (ECs) to help people who smoke achieve long-term smoking abstinence.

SEARCH METHODS

We searched the Cochrane Tobacco Addiction Group's Specialized Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, and PsycINFO to 1 February 2021, together with reference-checking and contact with study authors.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) and randomized cross-over trials in which people who smoke were randomized to an EC or control condition. We also included uncontrolled intervention studies in which all participants received an EC intervention. To be included, studies had to report abstinence from cigarettes at six months or longer and/or data on adverse events (AEs) or other markers of safety at one week or longer.

DATA COLLECTION AND ANALYSIS

We followed standard Cochrane methods for screening and data extraction. Our primary outcome measures were abstinence from smoking after at least six months follow-up, adverse events (AEs), and serious adverse events (SAEs). Secondary outcomes included changes in carbon monoxide, blood pressure, heart rate, blood oxygen saturation, lung function, and levels of known carcinogens/toxicants. We used a fixed-effect Mantel-Haenszel model to calculate the risk ratio (RR) with a 95% confidence interval (CI) for dichotomous outcomes. For continuous outcomes, we calculated mean differences. Where appropriate, we pooled data from these studies in meta-analyses.

MAIN RESULTS

We included 56 completed studies, representing 12,804 participants, of which 29 were RCTs. Six of the 56 included studies were new to this review update. Of the included studies, we rated five (all contributing to our main comparisons) at low risk of bias overall, 41 at high risk overall (including the 25 non-randomized studies), and the remainder at unclear risk. There was moderate-certainty evidence, limited by imprecision, that quit rates were higher in people randomized to nicotine EC than in those randomized to nicotine replacement therapy (NRT) (risk ratio (RR) 1.69, 95% confidence interval (CI) 1.25 to 2.27; I2 = 0%; 3 studies, 1498 participants). In absolute terms, this might translate to an additional four successful quitters per 100 (95% CI 2 to 8). There was low-certainty evidence (limited by very serious imprecision) that the rate of occurrence of AEs was similar) (RR 0.98, 95% CI 0.80 to 1.19; I2 = 0%; 2 studies, 485 participants). SAEs occurred rarely, with no evidence that their frequency differed between nicotine EC and NRT, but very serious imprecision led to low certainty in this finding (RR 1.37, 95% CI 0.77 to 2.41: I2 = n/a; 2 studies, 727 participants). There was moderate-certainty evidence, again limited by imprecision, that quit rates were higher in people randomized to nicotine EC than to non-nicotine EC (RR 1.70, 95% CI 1.03 to 2.81; I2 = 0%; 4 studies, 1057 participants). In absolute terms, this might again lead to an additional four successful quitters per 100 (95% CI 0 to 11). These trials mainly used older EC with relatively low nicotine delivery. There was moderate-certainty evidence of no difference in the rate of AEs between these groups (RR 1.01, 95% CI 0.91 to 1.11; I2 = 0%; 3 studies, 601 participants). There was insufficient evidence to determine whether rates of SAEs differed between groups, due to very serious imprecision (RR 0.60, 95% CI 0.15 to 2.44; I2 = n/a; 4 studies, 494 participants). Compared to behavioral support only/no support, quit rates were higher for participants randomized to nicotine EC (RR 2.70, 95% CI 1.39 to 5.26; I2 = 0%; 5 studies, 2561 participants). In absolute terms this represents an increase of seven per 100 (95% CI 2 to 17). However, this finding was of very low certainty, due to issues with imprecision and risk of bias. There was no evidence that the rate of SAEs differed, but some evidence that non-serious AEs were more common in people randomized to nicotine EC (AEs: RR 1.22, 95% CI 1.12 to 1.32; I2 = 41%, low certainty; 4 studies, 765 participants; SAEs: RR 1.17, 95% CI 0.33 to 4.09; I2 = 5%; 6 studies, 1011 participants, very low certainty). Data from non-randomized studies were consistent with RCT data. The most commonly reported AEs were throat/mouth irritation, headache, cough, and nausea, which tended to dissipate with continued use. Very few studies reported data on other outcomes or comparisons and hence evidence for these is limited, with confidence intervals often encompassing clinically significant harm and benefit.

AUTHORS' CONCLUSIONS

There is moderate-certainty evidence that ECs with nicotine increase quit rates compared to ECs without nicotine and compared to NRT. Evidence comparing nicotine EC with usual care/no treatment also suggests benefit, but is less certain. More studies are needed to confirm the size of effect, particularly when using modern EC products. Confidence intervals were for the most part wide for data on AEs, SAEs and other safety markers, though evidence indicated no difference in AEs between nicotine and non-nicotine ECs. Overall incidence of SAEs was low across all study arms. We did not detect any clear evidence of harm from nicotine EC, but longest follow-up was two years and the overall number of studies was small. The evidence is limited mainly by imprecision due to the small number of RCTs, often with low event rates. Further RCTs are underway. To ensure the review continues to provide up-to-date information, this review is now a living systematic review. We run searches monthly, with the review updated when relevant new evidence becomes available. Please refer to the Cochrane Database of Systematic Reviews for the review's current status.

Sensory experiences and cues among E-cigarette users

BACKGROUND AND AIMS

We characterized the extent and quality of respiratory sensations and sensory-related smoking cues associated with e-cigarette use among those who failed to quit combustible tobacco cigarette (CTC) use with traditional FDA approved medications but succeeded in doing so with e-cigarettes. Further, we sought to understand former smokers' perceptions about the influence of sensory experience with e-cigarette use on CTC cessation outcomes.

METHODS

A nonrandom purposive sample of 156 participants recruited in the USA through the Consumer Advocates for Smoke Free Alternatives Association Facebook page completed an online cross-sectional survey to assess sensory experiences and smoking cues associated with e-cigarette use. Descriptive statistics were calculated, and the ANOVA/Kruskal-Wallis test with post hoc testing and the two-sample t test/Wilcoxon rank-sum test, as appropriate based on distribution, were used to assess the association between sample characteristics and sensory experiences and cues using investigator constructed questions, the Modified Cigarette Evaluation Questionnaire (mCEQ) and the Smoking Cue Appeal Survey (SCAS).

RESULTS

With e-cigarette use, participants reported feeling the vapor in their throats, windpipes, noses, lungs, and on their tongues; reductions in nicotine craving; and enjoyment of their e-cigarette, including tasting, smelling, and seeing the vapor and touching the device. Women had greater craving reduction than men (p = 0.023). Those who began smoking at 13 years of age or younger had more satisfaction and had greater sensory enjoyment than those who began smoking at 16-17 years of age (p = 0.015 and p = 0.026, respectively), as well as greater sensory enjoyment than those who began smoking at 14-15 years of age (p = 0.047). There was a significant overall association between the number of years a respondent smoked and e-cigarette sensory enjoyment (p = 0.038). Participants 18-34 years old rated e-cigarettes as being more pleasant compared to 45 + years olds, (p = 0.012). Eighty-four percent of participants reported the sensation of the vapor as important in quitting CTCs, and 91% believed the sensations accompanying e-cigarette use contributed to their smoking cessation success.

CONCLUSIONS

For those who failed to quit previously using approved cessation medications to stop smoking cigarettes, sensory experiences associated with e-cigarette use may help smokers quit smoking.

Electronic cigarettes for smoking cessation

BACKGROUND

Electronic cigarettes (ECs) are handheld electronic vaping devices which produce an aerosol formed by heating an e-liquid. People who smoke report using ECs to stop or reduce smoking, but some organisations, advocacy groups and policymakers have discouraged this, citing lack of evidence of efficacy and safety. People who smoke, healthcare providers and regulators want to know if ECs can help people quit and if they are safe to use for this purpose. This review is an update of a review first published in 2014.

OBJECTIVES

To evaluate the effect and safety of using electronic cigarettes (ECs) to help people who smoke achieve long-term smoking abstinence.

SEARCH METHODS

We searched the Cochrane Tobacco Addiction Group's Specialized Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, and PsycINFO for relevant records to January 2020, together with reference-checking and contact with study authors.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) and randomized cross-over trials in which people who smoke were randomized to an EC or control condition. We also included uncontrolled intervention studies in which all participants received an EC intervention. To be included, studies had to report abstinence from cigarettes at six months or longer and/or data on adverse events (AEs) or other markers of safety at one week or longer.

DATA COLLECTION AND ANALYSIS

We followed standard Cochrane methods for screening and data extraction. Our primary outcome measures were abstinence from smoking after at least six months follow-up, AEs, and serious adverse events (SAEs). Secondary outcomes included changes in carbon monoxide, blood pressure, heart rate, blood oxygen saturation, lung function, and levels of known carcinogens/toxicants. We used a fixed-effect Mantel-Haenszel model to calculate the risk ratio (RR) with a 95% confidence interval (CI) for dichotomous outcomes. For continuous outcomes, we calculated mean differences. Where appropriate, we pooled data from these studies in meta-analyses.

MAIN RESULTS

We include 50 completed studies, representing 12,430 participants, of which 26 are RCTs. Thirty-five of the 50 included studies are new to this review update. Of the included studies, we rated four (all which contribute to our main comparisons) at low risk of bias overall, 37 at high risk overall (including the 24 non-randomized studies), and the remainder at unclear risk. There was moderate-certainty evidence, limited by imprecision, that quit rates were higher in people randomized to nicotine EC than in those randomized to nicotine replacement therapy (NRT) (risk ratio (RR) 1.69, 95% confidence interval (CI) 1.25 to 2.27; I2 = 0%; 3 studies, 1498 participants). In absolute terms, this might translate to an additional four successful quitters per 100 (95% CI 2 to 8). There was low-certainty evidence (limited by very serious imprecision) of no difference in the rate of adverse events (AEs) (RR 0.98, 95% CI 0.80 to 1.19; I2 = 0%; 2 studies, 485 participants). SAEs occurred rarely, with no evidence that their frequency differed between nicotine EC and NRT, but very serious imprecision led to low certainty in this finding (RR 1.37, 95% CI 0.77 to 2.41: I2 = n/a; 2 studies, 727 participants). There was moderate-certainty evidence, again limited by imprecision, that quit rates were higher in people randomized to nicotine EC than to non-nicotine EC (RR 1.71, 95% CI 1.00 to 2.92; I2 = 0%; 3 studies, 802 participants). In absolute terms, this might again lead to an additional four successful quitters per 100 (95% CI 0 to 12). These trials used EC with relatively low nicotine delivery. There was low-certainty evidence, limited by very serious imprecision, that there was no difference in the rate of AEs between these groups (RR 1.00, 95% CI 0.73 to 1.36; I2 = 0%; 2 studies, 346 participants). There was insufficient evidence to determine whether rates of SAEs differed between groups, due to very serious imprecision (RR 0.25, 95% CI 0.03 to 2.19; I2 = n/a; 4 studies, 494 participants). Compared to behavioural support only/no support, quit rates were higher for participants randomized to nicotine EC (RR 2.50, 95% CI 1.24 to 5.04; I2 = 0%; 4 studies, 2312 participants). In absolute terms this represents an increase of six per 100 (95% CI 1 to 14). However, this finding was very low-certainty, due to issues with imprecision and risk of bias. There was no evidence that the rate of SAEs varied, but some evidence that non-serious AEs were more common in people randomized to nicotine EC (AEs: RR 1.17, 95% CI 1.04 to 1.31; I2 = 28%; 3 studies, 516 participants; SAEs: RR 1.33, 95% CI 0.25 to 6.96; I2 = 17%; 5 studies, 842 participants). Data from non-randomized studies were consistent with RCT data. The most commonly reported AEs were throat/mouth irritation, headache, cough, and nausea, which tended to dissipate over time with continued use. Very few studies reported data on other outcomes or comparisons and hence evidence for these is limited, with confidence intervals often encompassing clinically significant harm and benefit.

AUTHORS' CONCLUSIONS

There is moderate-certainty evidence that ECs with nicotine increase quit rates compared to ECs without nicotine and compared to NRT. Evidence comparing nicotine EC with usual care/no treatment also suggests benefit, but is less certain. More studies are needed to confirm the degree of effect, particularly when using modern EC products. Confidence intervals were wide for data on AEs, SAEs and other safety markers. Overall incidence of SAEs was low across all study arms. We did not detect any clear evidence of harm from nicotine EC, but longest follow-up was two years and the overall number of studies was small. The main limitation of the evidence base remains imprecision due to the small number of RCTs, often with low event rates. Further RCTs are underway. To ensure the review continues to provide up-to-date information for decision-makers, this review is now a living systematic review. We will run searches monthly from December 2020, with the review updated as relevant new evidence becomes available. Please refer to the Cochrane Database of Systematic Reviews for the review's current status.

Nicotine or expectancies? Using the balanced-placebo design to test immediate outcomes of vaping

INTRODUCTION

Electronic (e-)cigarette use has increased in popularity, especially among those attempting to quit smoking. Previous studies evaluating the therapeutic efficacy of e-cigarettes have suggested that non-pharmacologic factors, such as expectancies about nicotine effects, may influence the experienced effects of e-cigarettes.

METHOD

The independent and synergistic influences of drug and expectancies were parsed using a balanced-placebo design, whereby 128 participants (52 dual users) were provided an e-cigarette that either contained nicotine or non-nicotine solution, while told that it did or did not contain nicotine. We hypothesized main effects of nicotine content on physiological, objective outcomes (attention, appetite, aversion, respiratory tract sensations), and main effects of the instructions on more subjective, psychosocial outcomes (affect, reward, satisfaction). Sex was included as a moderator.

RESULTS

Results showed that nicotine increased sustained attention, and more so among females. Nicotine delivery was associated with aversion among females, but not males. Among those who were both told and did not receive nicotine, higher enjoyment of respiratory tract sensations was reported. Nicotine with complementary instructions produced the highest reward ratings; additionally, nicotine was rewarding to males but not females.

DISCUSSION

Findings demonstrated that both nicotine content and non-pharmacologic factors impact acute outcome effects of e-cigarettes, with moderation by sex in some cases. Results are relevant to the interpretation of clinical trials of e-cigarettes and suggest a more nuanced view of reinforcement pathways.

Altered interoceptive processing in smokers: Evidence from the heartbeat tracking task

Neuroimaging evidence suggests that interoceptive processing might be altered in nicotine addiction, however this has not yet been confirmed with behavioural measures. Therefore, we investigated the perception of internal bodily states in smokers (n = 49) and people who had never smoked (n = 51), by measuring interoceptive accuracy (IAcc) and interoceptive sensibility (IS). IAcc was measured with a heartbeat tracking task and a heartbeat discrimination task. Performance on the heartbeat tracking task may be influenced by one's ability to estimate an elapsed time interval so this was controlled by also administering a time-estimation (TE) task. IS was measured using two sub-scales from the Multidimensional Assessment of Interoceptive Awareness (MAIA). All smokers completed the Revised Fagerström Test for Nicotine Dependence (FTND-R) to measure addiction severity. Non-smokers performed significantly better than smokers on the heartbeat tracking task. There were no significant group differences observed for the remaining variables. Furthermore, none of the variables predicted addiction severity. This is the first demonstration of behavioural differences in interoception between smokers and non-smokers.

Effect of menthol on nicotine intake and relapse vulnerability in a rat model of concurrent intravenous menthol/nicotine self-administration

RATIONALE

Epidemiological data suggest that menthol may increase vulnerability to cigarette/nicotine use and relapse. While menthol's sensory properties are often attributed as the underlying cause of the enhanced vulnerability, an alternative possibility is that they are mediated via pharmacological interactions with nicotine.

OBJECTIVE

This study addressed the possibility that menthol enhances nicotine intake and relapse vulnerability via pharmacological interactions with nicotine using a concurrent intravenous menthol/nicotine self-administration procedure.

METHODS

Following acquisition, adolescent rats were given 23-h/day access to nicotine (0.01 mg/kg/infusion), nicotine plus menthol (0.16, 0.32, or 0.64 mg/kg/infusion), or menthol alone (0.16, 0.32, 0.64 mg/kg/infusion) for a total of 10 days. Nicotine-seeking was assessed using an extinction/cue-induced reinstatement procedure following 10 days of forced abstinence. We also assessed the effect of menthol (0.32 mg/kg/infusion) on progressive ratio responding for nicotine (0.01 mg/kg/infusion).

RESULTS

Menthol decreased PR responding for nicotine but did not affect self-administration under extended access conditions. The low dose of menthol tended to decrease subsequent extinction responding, and was not different from menthol alone, whereas the high dose decreased reinstatement responding. Although not significant, the highest levels of extinction responding were observed in a minority of rats in the moderate and high menthol-nicotine groups; rats in these groups also took longer to extinguish.

CONCLUSIONS

Taken together, these results demonstrate that pharmacological interactions of menthol with nicotine reduce, rather than increase, nicotine's reinforcing effects and some measures of relapse vulnerability. Importantly, however, moderate and high menthol doses may increase some aspects of relapse vulnerability in a minority of individuals.

Stimulus effects of propylene glycol and vegetable glycerin in electronic cigarette liquids

BACKGROUND

Little is known about the behavioral effects of non-nicotine ingredients in electronic cigarette liquids. Propylene glycol (PG) and vegetable glycerin (VG) are the most common humectants used in electronic cigarette liquids. These ingredients may influence stimulus effects (e.g., visibility of exhalant, taste, or smell), which have played a role in the abuse liability of conventional cigarettes. In the current study, the stimulus effects of aerosol from liquids varying only in PG and VG content were assessed.

METHODS

Sixteen electronic cigarette users completed five sessions (one practice and four testing sessions). Following one hour of nicotine deprivation, two sampling puffs from liquid formulations containing 100/0, 75/25, 50/50, 25/75, and 0/100% PG/VG concentrations were administered in random order during five assessments, each separated by 20 min. Measures included self-reported stimulus effects and breakpoint on a multiple-choice procedure with options consisting of sampled puffs or varying amounts of money.

RESULTS

VG content was associated with greater reports of visibility of the exhalant (i.e., "cloud"). Liquids with only PG or VG engendered lower reports of inhalation sensations (e.g., throat hit) and greater reductions of systolic blood pressure compared to mixtures of PG and VG. There was no effect of liquid formulation on the multiple-choice procedure, but puffs were rarely chosen over even the smallest monetary option ($0.05), suggesting minimal reinforcing efficacy.

CONCLUSIONS

Liquids containing greater concentrations of VG are more capable of producing visible exhalant and mixtures of PG and VG engender greater airway sensory effects than either ingredient alone.

Effects of reduced nicotine content cigarettes on individual withdrawal symptoms over time and during abstinence

In the United States, the Food and Drug Administration (FDA) has initiated a public dialogue about reducing the nicotine content of cigarettes. A reduced-nicotine standard could increase withdrawal symptoms among current smokers. We examined the impact of switching smokers to cigarettes that varied in nicotine content on withdrawal symptoms over 6 weeks. A secondary analysis (N = 839) of a 10-site, double-blind clinical trial of nontreatment-seeking smokers was completed. Participants were instructed to smoke study cigarettes, containing 0.4 to 15.8 mg of nicotine/g of tobacco, for 6 weeks and were then abstinent overnight. Using latent growth curves, trajectories of individual withdrawal symptoms were compared between the reduced nicotine content (RNC) conditions and a normal nicotine content (NNC) condition. Path analyses compared symptoms after overnight abstinence. Relative to NNC cigarettes, participants smoking RNC cigarettes had increased anger/irritability/frustration and increased appetite/weight gain during the initial weeks, but the symptoms resolved by Week 6. Individuals who were biochemically verified as adherent with using only the 0.4 mg/g cigarettes had higher sadness levels (Cohen's d = .40) at Week 6 compared with the NNC condition, although symptoms were mild. After a post-Week 6 overnight abstinence challenge, some RNC conditions relative to NNC condition exhibited reduced withdrawal. Individuals who were biochemically confirmed as adherent to the lowest nicotine condition experienced only mild and transient symptom elevations. Thus, a reduced-nicotine standard for cigarettes produced a relatively mild and temporary increase in withdrawal among nontreatment-seeking smokers (ClinicalTrials.gov No. NCT01681875). (PsycINFO Database Record

Evaluation of menthol per se on acute perceptions and behavioral choice of cigarettes differing in nicotine content

Subjective perceptions and self-administration of cigarettes are each influenced by nicotine. Yet, differences specifically due to menthol in perceptions and choice of cigarettes varying in nicotine, and the association between these responses, have not been directly tested. Using a mixed between- and within-subjects design, acute responses to each of two menthol or non-menthol Spectrum research cigarettes, moderate (16-17 mg/g) versus very low (0.4 mg/g) in nicotine contents, were compared following brief abstinence in adult smokers preferring menthol ( n=44) or non-menthol ( n=29) brands. To ensure reliable perceptions, they experienced five exposures to each cigarette, then chose between them. All perceptions and choices were greater for moderate vs very low nicotine, as expected, and the magnitude of difference in four of six perceptions was associated with subsequently greater choice of the moderate nicotine cigarette. Importantly, virtually no differences were found between menthol and non-menthol, as nearly all perceptions, cigarette choices, and the association between perceptions and choice were not moderated by menthol or the interaction of nicotine by menthol. Our results indicate perceptions and reinforcement from cigarettes do not differ due to menthol when nicotine content and smoking topography are carefully controlled. Thus, regardless of menthol, smoking perceptions directly predict self-administration behavior.

Electronic cigarettes for smoking cessation

BACKGROUND

Electronic cigarettes (ECs) are electronic devices that heat a liquid into an aerosol for inhalation. The liquid usually comprises propylene glycol and glycerol, with or without nicotine and flavours, and stored in disposable or refillable cartridges or a reservoir. Since ECs appeared on the market in 2006 there has been a steady growth in sales. Smokers report using ECs to reduce risks of smoking, but some healthcare organizations, tobacco control advocacy groups and policy makers have been reluctant to encourage smokers to switch to ECs, citing lack of evidence of efficacy and safety. Smokers, healthcare providers and regulators are interested to know if these devices can help smokers quit and if they are safe to use for this purpose. This review is an update of a review first published in 2014.

OBJECTIVES

To evaluate the safety and effect of using ECs to help people who smoke achieve long-term smoking abstinence.

SEARCH METHODS

We searched the Cochrane Tobacco Addiction Group's Specialized Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, and PsycINFO for relevant records from 2004 to January 2016, together with reference checking and contact with study authors.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) in which current smokers (motivated or unmotivated to quit) were randomized to EC or a control condition, and which measured abstinence rates at six months or longer. As the field of EC research is new, we also included cohort follow-up studies with at least six months follow-up. We included randomized cross-over trials, RCTs and cohort follow-up studies that included at least one week of EC use for assessment of adverse events (AEs).

DATA COLLECTION AND ANALYSIS

We followed standard Cochrane methods for screening and data extraction. Our main outcome measure was abstinence from smoking after at least six months follow-up, and we used the most rigorous definition available (continuous, biochemically validated, longest follow-up). We used a fixed-effect Mantel-Haenszel model to calculate the risk ratio (RR) with a 95% confidence interval (CI) for each study, and where appropriate we pooled data from these studies in meta-analyses.

MAIN RESULTS

Our searches identified over 1700 records, from which we include 24 completed studies (three RCTs, two of which were eligible for our cessation meta-analysis, and 21 cohort studies). Eleven of these studies are new for this version of the review. We identified 27 ongoing studies. Two RCTs compared EC with placebo (non-nicotine) EC, with a combined sample size of 662 participants. One trial included minimal telephone support and one recruited smokers not intending to quit, and both used early EC models with low nicotine content and poor battery life. We judged the RCTs to be at low risk of bias, but under the GRADE system we rated the overall quality of the evidence for our outcomes as 'low' or 'very low', because of imprecision due to the small number of trials. A 'low' grade means that further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. A 'very low' grade means we are very uncertain about the estimate. Participants using an EC were more likely to have abstained from smoking for at least six months compared with participants using placebo EC (RR 2.29, 95% CI 1.05 to 4.96; placebo 4% versus EC 9%; 2 studies; 662 participants. GRADE: low). The one study that compared EC to nicotine patch found no significant difference in six-month abstinence rates, but the confidence intervals do not rule out a clinically important difference (RR 1.26, 95% CI 0.68 to 2.34; 584 participants. GRADE: very low).Of the included studies, none reported serious adverse events considered related to EC use. The most frequently reported AEs were mouth and throat irritation, most commonly dissipating over time. One RCT provided data on the proportion of participants experiencing any adverse events. The proportion of participants in the study arms experiencing adverse events was similar (ECs vs placebo EC: RR 0.97, 95% CI 0.71 to 1.34 (298 participants); ECs vs patch: RR 0.99, 95% CI 0.81 to 1.22 (456 participants)). The second RCT reported no statistically significant difference in the frequency of AEs at three- or 12-month follow-up between the EC and placebo EC groups, and showed that in all groups the frequency of AEs (with the exception of throat irritation) decreased significantly over time.

AUTHORS' CONCLUSIONS

There is evidence from two trials that ECs help smokers to stop smoking in the long term compared with placebo ECs. However, the small number of trials, low event rates and wide confidence intervals around the estimates mean that our confidence in the result is rated 'low' by GRADE standards. The lack of difference between the effect of ECs compared with nicotine patches found in one trial is uncertain for similar reasons. None of the included studies (short- to mid-term, up to two years) detected serious adverse events considered possibly related to EC use. The most commonly reported adverse effects were irritation of the mouth and throat. The long-term safety of ECs is unknown. In this update, we found a further 15 ongoing RCTs which appear eligible for this review.

Does Extended Pre Quit Bupropion Aid in Extinguishing Smoking Behavior?

INTRODUCTION

Understanding the mechanisms by which bupropion promotes smoking cessation may lead to more effective treatment. To the extent that reduced smoking reinforcement is one such mechanism, a longer duration of pre quit bupropion treatment should promote extinction of smoking behavior. We evaluated whether 4 weeks of pre quit bupropion (extended run-in) results in greater pre quit reductions in smoking rate and cotinine and, secondarily, greater short-term abstinence, than standard 1 week of pre quit bupropion (standard run-in).

METHODS

Adult smokers (n = 95; 48 females) were randomized to a standard run-in group (n = 48; 3-week placebo, then 1-week bupropion pre quit) or an extended run-in group (4-week pre quit bupropion; n = 47). Both groups received group behavioral counseling and 7 weeks of post quit bupropion. Smoking rate (and craving, withdrawal, and subjective effects) was collected daily during the pre quit period; biochemical data (cotinine and carbon monoxide) were collected at study visits.

RESULTS

During the pre quit period, the extended run-in group exhibited a greater decrease in smoking rate, compared to the standard run-in group, interaction p = .03. Cigarette craving and salivary cotinine followed a similar pattern, though the latter was evident only among women. Biochemically verified 4-week continuous abstinence rates were higher in the extended run-in group (53%) than the standard run-in group (31%), p = .033.

CONCLUSIONS

The extended use of bupropion prior to a quit attempt reduces smoking behavior during the pre quit period and improved short-term abstinence rates. The data are consistent with an extinction-of-reinforcement model and support further investigation of extended run-in bupropion therapy for smoking cessation.

Reinforcement enhancing effects of acute nicotine via electronic cigarettes

BACKGROUND

Recent human studies confirm animal research showing that nicotine enhances reinforcement from rewards unrelated to nicotine. These effects of acute nicotine via tobacco smoking may also occur when consumed from non-tobacco products.

METHODS

We assessed acute effects of nicotine via electronic cigarettes ("e-cigarettes") on responding reinforced by music, video, or monetary rewards, or for no reward (control). In a fully within-subjects design, adult dependent smokers (N=28) participated in three similar experimental sessions, each following overnight abstinence (verified by CO≤10ppm). Varying only in e-cigarette condition, sessions involved controlled exposure to a nicotine (labeled "36mg/ml") or placebo ("0″) e-cigarette, or no e-cigarette use. A fourth session involved smoking one's own tobacco cigarette brand after no abstinence, specifically to compare responses under typical nicotine satiation with these acute e-cigarette conditions after abstinence.

RESULTS

Reinforced responding for video reward, but not the other rewards, was greater due to use of the nicotine versus placebo e-cigarette (i.e., nicotine per se), while no differences were found between the placebo e-cigarette and no e-cigarette conditions (i.e., e-cigarette use per se). For nicotine via tobacco smoking, responding compared to the nicotine e-cigarette was similar for video but greater for music, while both video and music reward were enhanced relative to the non-nicotine conditions (placebo and no e-cigarette).

CONCLUSIONS

Acute nicotine from a non-tobacco product has some reinforcement enhancing effects in humans, in a manner partly consistent with nicotine via tobacco smoking and perhaps contributing to the rising popularity of nicotine e-cigarette use.

Smoking Through a Topography Device Diminishes Some of the Acute Rewarding Effects of Smoking

BACKGROUND

Smoking topography (ST) devices are an important methodological tool for quantifying puffing behavior (eg, puff volume, puff velocity) as well as identifying puffing differences across individuals and situations. Available ST devices are designed such that the smoker's mouth and hands have direct contact with the device rather than the cigarette itself. Given the importance of the sensorimotor aspects of cigarette smoking in smoking reward, it is possible that ST devices may interfere with the acute rewarding effects of smoking. Despite the methodological importance of this issue, few studies have directly compared subjective reactions to smoking through a topography device to naturalistic smoking.

METHODS

Smokers (N = 58; 38% female) smoked their preferred brand of cigarettes one time through a portable topography device and one time naturalistically, in counterbalanced order across two laboratory sessions. Smoking behavior (eg, number of puffs) and subjective effects (eg, urge reduction, affect, smoking satisfaction) were assessed.

RESULTS

Negative affect reduction was greater in the natural smoking condition relative to the topography condition, but differences were not significant on measures of urge, withdrawal, or positive affect. Self-reported smoking satisfaction, enjoyment of respiratory tract sensations, psychological reward, craving reduction, and other rewarding effects of smoking were also significantly greater in the naturalistic smoking condition.

CONCLUSIONS

The effects of using a ST device on the smoking experience should be considered when it is used in research as it may diminish some of the rewarding effects of smoking.

IMPLICATIONS

When considering the inclusion of a smoking topography device in one's research, it is important to know if use of that device will alter the smoker's experience. This study assessed affective and subjective reactions to smoking through a topography device compared to naturalistic smoking. We found that smoking satisfaction, psychological reward, enjoyment of respiratory tract sensations and other rewarding effects were all diminished when smoking through the topography device. The effects of using a smoking topography device on the smoking experience should be considered when it is used in future research.

Predicted Impact of Nicotine Reduction on Smokers with Affective Disorders

OBJECTIVES

In 2009 the FDA acquired the authority to reduce the nicotine content in cigarettes if appropriate for public health, prompting research to evaluate the implications of this policy scientifically. Studies in non-psychiatric populations show that reducing the nicotine content of cigarettes to non-addictive levels reduces smoking rates and nicotine dependence. However, few studies have examined this hypothesis in vulnerable populations.

METHODS

In this narrative review we examined the extant literature on the effects of nicotine reduction or cessation on symptoms of withdrawal, as well as psychiatric symptoms, among those with affective disorders.

RESULTS

Following initial withdrawal from nicotine, smokers with affective disorders experience more severe mood disruption than smokers without these disorders. Use of very low nicotine content (VLNC) cigarettes during abstinence may help mitigate the mood-disrupting effects of initial abstinence. Once the initial effects of nicotine withdrawal on mood have passed, longer-term abstinence is associated with psychiatric improvement rather than worsening.

CONCLUSIONS

These findings suggest that if a national nicotine reduction policy were to be implemented, smokers with affective disorders would need additional support to overcome initial withdrawal but that long-term outcomes would likely be positive.

Initial Evaluation of Fenofibrate for Efficacy in Aiding Smoking Abstinence

INTRODUCTION

Primate and rodent models show that peroxisome proliferator-activated receptor-alpha (PPAR-α) ligands, including fibrate medications, reduce nicotine reinforcement, reward, and related effects. We tested fenofibrate, the most common U.S. Food and Drug Administration-approved fibrate for lipid control versus placebo for initial evidence of efficacy in smoking cessation using a validated cross-over procedure for early Phase 2 evaluations.

METHODS

Adult dependent smokers (N = 38) in this 4-week within-subjects study were those already intending to try to quit in the next 2 months. All smoked ad libitum during weeks 1 (baseline) and 3 (washout) and began fenofibrate (160 mg/d; dosing approved for lipid control) or placebo near the end of weeks 1 and 3. Following each 4-day dose run-up, they were then instructed to try to quit for 4 days (Tuesday-Friday) during weeks 2 and 4, with the order of medication conditions counter-balanced and administered double-blind. Abstinence was verified daily in each 4-day quit period by self-report of no smoking in the prior 24 hours and carbon monoxide < 5 ppm. Secondary measures of acute smoking reinforcement and cue reactivity prior to quitting, and smoking reduction when trying to quit, were also assessed.

RESULTS

No differences between fenofibrate versus placebo were found on days quit (means ± SEM of 1.8±0.3 vs. 1.9±0.3, respectively). Similarly, there were no differences in any of the secondary measures (all P > .20).

CONCLUSIONS

Although higher dosing or other proliferator-activated receptor-alpha agonists may show efficacy, this study indicates that fenofibrate does not aid ability to stop smoking during a brief practice quit period in dependent smokers high in current quit interest.

Sex differences in acute relief of abstinence-induced withdrawal and negative affect due to nicotine content in cigarettes

INTRODUCTION

Acute cigarette smoking may relieve withdrawal and negative affect due to tobacco abstinence to a greater extent in women versus men. Yet, the relative contribution of the cigarette's nicotine content to this sex difference is not clear.

METHODS

Non-quitting dependent adult smokers (N = 44; 21 males, 23 females) participated in 2 virtually identical sessions, each after abstaining overnight (CO < 10 ppm) and differing only in the nicotine content of the designated cigarette. While blind to brand markings, they consumed a total of 24 puffs in controlled fashion for 2 hr in each session, either from a nicotine (Quest 1, 0.6 mg) or denicotinized (Quest 3, 0.05 mg) cigarette. Withdrawal symptoms were obtained before and after smoking, and negative affect was assessed after each period of cigarette exposure consisting of 6 puffs every 25 min.

RESULTS

Men and women did not differ in baseline withdrawal and negative affect due to overnight abstinence, but reductions in each symptom were significantly influenced by the interaction of sex × nicotine/denicotinized cigarette (both p < .05). In men, but not in women, each symptom was generally decreased more by the nicotine versus denicotinized cigarette, and the nicotine cigarette reduced each to a greater degree in men versus women.

CONCLUSIONS

Sex differences in relief of abstinence-induced withdrawal and negative affect due to the nicotine content in cigarettes are consistent with prior research indicating that nicotine per se, compared to non-nicotine smoke stimuli, is less rewarding in women versus men.

Neuroanatomical circuitry mediating the sensory impact of nicotine in the central nervous system

Direct actions of nicotine in the CNS appear to be essential for its reinforcing properties. However, activation of nicotinic acetylcholine receptors (nAChRs) on afferent sensory nerve fibers is an important component of addiction to, and withdrawal from, cigarette smoking. The aim of the present study was to identify the neuroanatomical substrates activated by the peripheral actions of nicotine and to determine whether these sites overlap brain structures stimulated by direct actions of nicotine. Mouse brains were examined by immunohistochemistry for c-Fos protein after intraperitoneal injection of either nicotine hydrogen tartrate salt (NIC; 30 and 40 μg/kg) or nicotine pyrrolidine methiodide (NIC-PM; 20 and 30 μg/kg). NIC-PM induced c-Fos immunoreactivity (IR) at multiple brain sites. In the brainstem, c-Fos IR was detected in the locus coeruleus, laterodorsal tegmental nucleus, and pedunculotegmental nucleus. In the midbrain, c-Fos IR was observed in areas overlapping the ventral tegmental area (VTA), which includes the paranigral nucleus, parainterfascicular nucleus, parabrachial pigmental area, and rostral VTA. Other structures of the nicotine brain-reward circuitry activated by NIC-PM included the hypothalamus, paraventricular thalamic nucleus, lateral habenular nucleus, hippocampus, amygdala, accumbens nucleus, piriform cortex, angular insular cortex, anterior olfactory nucleus, lateral septal nucleus, bed nucleus of stria terminalis, cingulate and medial prefrontal cortex, olfactory tubercle, and medial and lateral orbital cortex. NIC, acting through central and peripheral nAChRs, produced c-Fos IR in areas that overlapped NIC-PM-induced c-Fos-expressing sites. These neuroanatomical data are the first to demonstrate that the CNS structures that are the direct targets of nicotine are also anatomical substrates for the peripheral sensory impact of nicotine.

Critical role of peripheral sensory systems in mediating the neural effects of nicotine following its acute and repeated exposure

It is well established that the reinforcing properties of nicotine (NIC) depend on its action on nicotinic acetylcholine receptors expressed by brain neurons. However, when administered systemically, NIC first phasically activates nicotinic receptors located on the afferents of sensory nerves at the sites of drug administration before reaching the brain and directly interacting with central neurons. While this peripheral action of NIC has been known for years, it is usually neglected in any consideration of the drug's reinforcing properties and experience-dependent changes of its behavioral and physiological effects. The goal of this work was to review our recent behavioral, electrophysiological, and physiological data suggesting the critical importance of peripheral actions of NIC in mediating its neural effects following acute drug exposure and their involvement in alterations of NIC effects consistently occurring following repeated drug exposure. Because NIC, by acting peripherally, produces a rapid sensory signal to the central nervous system that is followed by slower, more prolonged direct drug actions in the brain, these two pharmacological actions interact in the central nervous system during repeated drug use with the development of Pavlovian conditioned association. This within-drug conditioning mechanism could explain the experience-dependent changes in the physiological, behavioral, and human psychoemotional effects of NIC, which, in drug-experienced individuals, always represent a combination of pharmacological and learning variables.

Electronic cigarettes for smoking cessation and reduction

BACKGROUND

Electronic cigarettes (ECs) are electronic devices that heat a liquid - usually comprising propylene glycol and glycerol, with or without nicotine and flavours, stored in disposable or refillable cartridges or a reservoir - into an aerosol for inhalation. Since ECs appeared on the market in 2006 there has been a steady growth in sales. Smokers report using ECs to reduce risks of smoking, but some healthcare organisations have been reluctant to encourage smokers to switch to ECs, citing lack of evidence of efficacy and safety. Smokers, healthcare providers and regulators are interested to know if these devices can reduce the harms associated with smoking. In particular, healthcare providers have an urgent need to know what advice they should give to smokers enquiring about ECs.

OBJECTIVES

To examine the efficacy of ECs in helping people who smoke to achieve long-term abstinence; to examine the efficacy of ECs in helping people reduce cigarette consumption by at least 50% of baseline levels; and to assess the occurrence of adverse events associated with EC use.

SEARCH METHODS

We searched the Cochrane Tobacco Addiction Groups Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, and two other databases for relevant records from 2004 to July 2014, together with reference checking and contact with study authors.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) in which current smokers (motivated or unmotivated to quit) were randomized to EC or a control condition, and which measured abstinence rates or changes in cigarette consumption at six months or longer. As the field of EC research is new, we also included cohort follow-up studies with at least six months follow-up. We included randomized cross-over trials and cohort follow-up studies that included at least one week of EC use for assessment of adverse events.

DATA COLLECTION AND ANALYSIS

One review author extracted data from the included studies and another checked them. Our main outcome measure was abstinence from smoking after at least six months follow-up, and we used the most rigorous definition available (continuous, biochemically validated, longest follow-up). For reduction we used a dichotomous approach (no change/reduction < 50% versus reduction by 50% or more of baseline cigarette consumption). We used a fixed-effect Mantel-Haenszel model to calculate the risk ratio (RR) with a 95% confidence interval (CI) for each study, and where appropriate we pooled data from these studies in meta-analyses.

MAIN RESULTS

Our search identified almost 600 records, from which we include 29 representing 13 completed studies (two RCTs, 11 cohort). We identified nine ongoing trials. Two RCTs compared EC with placebo (non-nicotine) EC, with a combined sample size of 662 participants. One trial included minimal telephone support and one recruited smokers not intending to quit, and both used early EC models with low nicotine content. We judged the RCTs to be at low risk of bias, but under the GRADE system the overall quality of the evidence for our outcomes was rated 'low' or 'very low' because of imprecision due to the small number of trials. A 'low' grade means that further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. A 'very low' grade means we are very uncertain about the estimate. Participants using an EC were more likely to have abstained from smoking for at least six months compared with participants using placebo EC (RR 2.29, 95% CI 1.05 to 4.96; placebo 4% versus EC 9%; 2 studies; GRADE: low). The one study that compared EC to nicotine patch found no significant difference in six-month abstinence rates, but the confidence intervals do not rule out a clinically important difference (RR 1.26, 95% CI: 0.68 to 2.34; GRADE: very low). A higher number of people were able to reduce cigarette consumption by at least half with ECs compared with placebo ECs (RR 1.31, 95% CI 1.02 to 1.68, 2 studies; placebo: 27% versus EC: 36%; GRADE: low) and compared with patch (RR 1.41, 95% CI 1.20 to 1.67, 1 study; patch: 44% versus EC: 61%; GRADE: very low). Unlike smoking cessation outcomes, reduction results were not biochemically verified.None of the RCTs or cohort studies reported any serious adverse events (SAEs) that were considered to be plausibly related to EC use. One RCT provided data on the proportion of participants experiencing any adverse events. Although the proportion of participants in the study arms experiencing adverse events was similar, the confidence intervals are wide (ECs vs placebo EC RR 0.97, 95% CI 0.71 to 1.34; ECs vs patch RR 0.99, 95% CI 0.81 to 1.22). The other RCT reported no statistically significant difference in the frequency of AEs at three- or 12-month follow-up between the EC and placebo EC groups, and showed that in all groups the frequency of AEs (with the exception of throat irritation) decreased significantly over time.

AUTHORS' CONCLUSIONS

There is evidence from two trials that ECs help smokers to stop smoking long-term compared with placebo ECs. However, the small number of trials, low event rates and wide confidence intervals around the estimates mean that our confidence in the result is rated 'low' by GRADE standards. The lack of difference between the effect of ECs compared with nicotine patches found in one trial is uncertain for similar reasons. ECs appear to help smokers unable to stop smoking altogether to reduce their cigarette consumption when compared with placebo ECs and nicotine patches, but the above limitations also affect certainty in this finding. In addition, lack of biochemical assessment of the actual reduction in smoke intake further limits this evidence. No evidence emerged that short-term EC use is associated with health risk.

Escalating doses of transdermal nicotine in heavy smokers: effects on smoking behavior and craving

Fixed-dose nicotine replacement therapy (NRT) is efficacious for smoking cessation in the general population of smokers. However, it is less effective in populations with psychiatric comorbidities and/or severe tobacco dependence where the percent nicotine replacement is suboptimal. The objective of this pilot study was to determine the effectiveness of nicotine patch dose titration in response to continued smoking in heavily dependent smokers with psychiatric comorbidity. In a single-arm, open-label study adult smokers (mean cigarettes per day, 25.4 ± 13.4; range, 14-43; n = 12) willing to quit were treated with escalating doses of transdermal nicotine and brief counseling intervention if they continued to smoke over a 9-week treatment period. Plasma nicotine and cotinine, along with expired carbon monoxide levels, and the subjective effects of smoking, urge to smoke, demand elasticity, and mood symptoms were also assessed. The mean NRT dose was 32.7 (SD, 16.4) mg/d (range, 7-56 mg/d). Smokers reported significant reductions in both cigarettes per day (mean decrease, 18.4 ± 11.5) confirmed by expired carbon monoxide (mean decrease, 13.5 ± 13.0) with no significant changes in plasma nicotine concentrations during the course of NRT dose titration. There were significant effects on the subjective effects of smoking and measures of smoking behavior. Most commonly reported adverse events were respiratory infections, skin irritation at patch site, nausea, and sleep disturbances, which were generally mild and transient. Titrating doses of NRT to effect with brief intervention hold promise as an effective clinical strategy to assist heavily dependent psychiatrically ill smokers to change their smoking behavior.

Rapid sensitization of physiological, neuronal, and locomotor effects of nicotine: critical role of peripheral drug actions

Repeated exposure to nicotine and other psychostimulant drugs produces persistent increases in their psychomotor and physiological effects (sensitization), a phenomenon related to the drugs' reinforcing properties and abuse potential. Here we examined the role of peripheral actions of nicotine in nicotine-induced sensitization of centrally mediated physiological parameters (brain, muscle, and skin temperatures), cortical and VTA EEG, neck EMG activity, and locomotion in freely moving rats. Repeated injections of intravenous nicotine (30 μg/kg) induced sensitization of the drug's effects on all these measures. In contrast, repeated injections of the peripherally acting analog of nicotine, nicotine pyrrolidine methiodide (nicotine(PM), 30 μg/kg, i.v.) resulted in habituation (tolerance) of the same physiological, neuronal, and behavioral measures. However, after repeated nicotine exposure, acute nicotine(PM) injections induced nicotine-like physiological responses: powerful cortical and VTA EEG desynchronization, EMG activation, a large brain temperature increase, but weaker hyperlocomotion. Additionally, both the acute locomotor response to nicotine and nicotine-induced locomotor sensitization were attenuated by blockade of peripheral nicotinic receptors by hexamethonium (3 mg/kg, i.v.). These data suggest that the peripheral actions of nicotine, which precede its direct central actions, serve as a conditioned interoceptive cue capable of eliciting nicotine-like physiological and neural responses after repeated nicotine exposure. Thus, by providing a neural signal to the CNS that is repeatedly paired with the direct central effects of nicotine, the drug's peripheral actions play a critical role in the development of nicotine-induced physiological, neural, and behavioral sensitization.

A rodent "self-report" measure of methamphetamine craving? Rat ultrasonic vocalizations during methamphetamine self-administration, extinction, and reinstatement

Rats emit ultrasonic vocalizations (USVs) in a variety of contexts, and it is increasingly clear that USVs reflect more complex information than mere positive and negative affect states. We sought to examine USVs in a common model of addiction and relapse, the self-administration/reinstatement paradigm, in order to gain insight into subjective states experienced by rats during various types of methamphetamine seeking. We measured three subtypes of "50kHz" USVs [flats, trills, and non-trill frequency modulated (FM) USVs], as well as long and short duration "22kHz" USVs, during self-administration and extinction training, and during reinstatement elicited by cues, a methamphetamine prime, cues+prime, or the pharmacological stressor yohimbine. During self-administration and extinction, rats emitted many flats and FMs, (and short duration "22kHz" USVs on day 1 of self-administration), but few trills. In contrast, methamphetamine priming injections potently enhanced FMs and trills, and trill production was correlated with the degree of methamphetamine+cue-elicited reinstatement. Cues alone yielded increases only in flat USVs during reinstatement, though a subset of rats displaying strong cue-induced reinstatement also emitted long duration, aversion-related "22kHz" USVs. Although yohimbine administration caused reinstatement, it did not induce "22kHz" USVs in methamphetamine-experienced or methamphetamine-naïve rats (unlike footshock stress, which did induce long duration "22kHz" USVs). These findings demonstrate heterogeneity of rat USVs emitted during different types of methamphetamine seeking, and highlight their potential usefulness for gaining insight into the subjective states of rats in rodent models of drug addiction and relapse.

Acute cigarette smoking reduces latencies on a Smoking Stroop test

RATIONALE

Sensitivity to addiction-related cues, a type of attentional bias, may interfere with executive functions that are important in sustaining abstinence from drug abuse. Assessments of attentional bias in research participants who smoke cigarettes have used Smoking Stroop tasks, which are variations of emotional Stroop tasks in which the stimuli are smoking-related and neutral words.

OBJECTIVES

We aimed to determine the effect of resumption of smoking by deprived cigarette smokers on attentional bias.

METHODS

Testing occurred twice on each of two test days. One test day began after overnight abstinence (13-16h) and the other after <1h of abstinence. The participants (n=51) smoked a cigarette between the two test sessions on each test day.

RESULTS

Smokers exhibited attentional bias for smoking-related words and had longer response times after overnight abstinence than after brief abstinence. Cigarette smoking between sessions reduced response times on both test days with no interaction by stimulus type.

CONCLUSIONS

Smoking-related cues have distracting effects in smokers, and smoking reduces response latency, with no specific effect on attentional bias. The increase in response speed may contribute to a smoker's impression that abstinence hinders performance and that smoking reverses impairment.

Separate and combined effects of very low nicotine cigarettes and nicotine replacement in smokers with schizophrenia and controls

INTRODUCTION

The prevalence of smoking among people with schizophrenia in the United States is about 3 times that of the general population. Novel approaches are needed to reduce rates of smoking-related morbidity and mortality among these smokers.

METHODS

This study used a within-subjects design to investigate the separate and combined effects of sensorimotor replacement for smoking (very low nicotine content [VLNC] cigarettes vs. no cigarettes) and transdermal nicotine replacement (42 mg nicotine [NIC] vs. placebo [PLA] patches) in smokers with schizophrenia (SS; n = 30) and control smokers without psychiatric illness (CS; n = 26). Each session contained a 5-hr controlled administration period in which participants underwent the following conditions, in counterbalanced order: VLNC + NIC, VLNC + PLA, no cigarettes + NIC, no cigarettes + PLA, usual-brand cigarettes + no patches. Next, participants completed measures of cigarette craving, nicotine withdrawal, smoking habit withdrawal, and cigarette subjective effects, followed by a 90-min period of ad libitum usual-brand smoking.

RESULTS

Smoking VLNC cigarettes during the controlled administration periods reduced cigarette craving, nicotine withdrawal symptoms, habit withdrawal symptoms, and usual-brand smoking in SS and CS relative to the no cigarette conditions. VLNC cigarettes were well accepted by both groups and did not affect psychiatric symptom levels in SS. Transdermal nicotine significantly reduced cigarette craving but did not affect usual-brand smoking.

CONCLUSIONS

These findings suggest that reducing the nicotine content of cigarettes to nonaddictive levels may be a promising approach for reducing nicotine dependence among people with schizophrenia.

Smoking in response to negative mood in men versus women as a function of distress tolerance

INTRODUCTION

Negative mood situations often increase smoking behavior and reward, effects that may be greater among women and smokers low in tolerance for distress.

METHODS

Adult dependent smokers (N = 164; 86 men, 78 women) first completed measures of distress tolerance via self-report and by mirror-tracing and breath-holding tasks. They then participated in 2 virtually identical laboratory sessions, involving induction of negative versus neutral mood (control) via pictorial slides and music. They rated negative affect (NA) before and during mood induction and smoked their preferred brand ad libitum during the last 14 min of mood induction. Our aim was to examine mood effects on NA, smoking reward ("liking"), and smoking intake (puff volume and number) as a function of sex and distress tolerance.

RESULTS

Negative mood induction increased NA, as planned, and smoking reward and intake compared with neutral mood. Increases in NA and puff volume due to negative mood were greater in women compared with men, as hypothesized, but no main effects of the self-report or behavioral distress tolerance measures were seen in responses to mood induction. However, unexpectedly, lower self-reported distress tolerance was associated with greater smoking intake due to negative (but not neutral) mood in men and generally due to neutral (but not negative) mood in women.

CONCLUSIONS

Negative mood may increase smoking intake more in women compared with men. Yet, low distress tolerance may enhance smoking intake due to negative versus neutral mood differentially between women and men, suggesting that sex and distress tolerance may interact to influence smoking responses to negative mood.

Decreasing Nicotine Content Reduces Subjective and Physiological Effects of Smoking

OBJECTIVE

Assessment of the subjective and physiological effects of smoking cigarettes with different machine-smoked nicotine yields.

METHODS

Eight volunteers rated the characteristics of cigarettes with varying levels of nicotine (Quest^®). At 30 minute intervals, participants smoked one of three different Quest^® brand cigarettes in a counterbalanced order (reported machine-smoked nicotine yield: 0.6 mg, 0.3 mg, or 0.05 mg). Smoking satisfaction and sensations were measured on a cigarette evaluation questionnaire. A mood questionnaire measured self-reported subjective changes in 'happy', 'stimulated', 'anxious', 'desire to smoke', and 'desire not to smoke'. Heart rate and skin temperature were recorded continuously.

RESULTS

As nicotine yield decreased, cigarettes produced smaller changes in subjective ratings on the evaluation questionnaire with the placebo nicotine cigarette always rated lower or less potent than the other two cigarettes evaluated. Heart rate was significantly increased by the reduced nicotine cigarettes, but was not affected by the nicotine-free cigarette.

CONCLUSION

These results indicate that machine-smoked yield is an important determinant of both the subjective and physiological effects of smoking. The use of reduced and nicotine free cigarettes in smoking cessation programs remains to be evaluated.

The reliability of puff topography and subjective responses during ad lib smoking of a single cigarette

INTRODUCTION

Acute smoking behavior (i.e., puff topography) and subjective responses during the ad lib smoking of a single cigarette in the laboratory may provide useful measures of smoking reinforcement and reward, respectively. However, the reliability of such measures is not clear, leaving uncertain the utility of a single assessment of smoking behavior as an individual difference measure.

METHODS

Dependent smokers (N = 94) smoked normally prior to each of 4 laboratory sessions during which they were instructed to smoke 1 cigarette of their preferred brand in ad libitum and unblinded fashion and then rate it for subjective effects. Puff topography (puff number, total volume, and maximum volume) was assessed via portable Clinical Research Support System device. Subjective reward and perception were assessed by visual analog scales of "liking" and "how strong," respectively. The reliability of puff topography and subjective measures was determined across days by intra-class correlations (ICCs). Differences due to sex and nicotine dependence (high and low Fagerström Test for Nicotine Dependence score) were also examined.

RESULTS

Reliability was highly significant for each measure. ICCs were .70 for total puff volume, .60 for maximum puff volume, .73 for puff number, .64 for liking, and .78 for how strong. Reliability generally did not differ by sex or dependence, but absolute values for total volume and maximum puff volume were greater in men and in high dependent smokers. Liking was also greater in high dependent smokers.

CONCLUSIONS

Puff topography and subjective measures during the ad lib smoking of a single cigarette are highly reliable. Smoking responses during a single ad lib smoking session may be useful in identifying stable individual differences in smoking reinforcement and reward.

Nicotine reduction revisited: science and future directions

Regulation of nicotine levels in cigarettes and other tobacco products is now possible with the passage of the Family Smoking Prevention and Tobacco Control Act (FSPTCA) in 2009, giving the US Food and Drug Administration (FDA) authority to regulate tobacco products, and with Articles 9-11 of the WHO Framework Convention on Tobacco Control. Both regulatory approaches allow establishing product standards for tobacco constituents, including nicotine. The FSPTCA does not allow nicotine levels to be decreased to zero, although the FDA has the authority to reduce nicotine yields to very low, presumably non-addicting levels. The proposal to reduce levels of nicotine to a level that is non-addicting was originally suggested in 1994. Reduction of nicotine in tobacco products could potentially have a profound impact on reducing tobacco-related morbidity and mortality. To examine this issue, two meetings were convened in the US with non-tobacco-industry scientists of varied disciplines, tobacco control policymakers and representatives of government agencies. This article provides an overview of the current science in the area of reduced nicotine content cigarettes and key conclusions and recommendations for research and policy that emerged from the deliberations of the meeting members.

The insula and drug addiction: an interoceptive view of pleasure, urges, and decision-making

We have recently shown that damage to the insula leads to a profound disruption of addiction to cigarette smoking (Naqvi et al., Science 315:531-534, 2007). Yet, there is little understanding of why the insula should play such an important role in an addictive behavior. A broad literature (much of it reviewed in this issue) has addressed the role of the insula in processes related to conscious interoception, emotional experience, and decision-making. Here, we review evidence for the role of the insula in drug addiction, and propose a novel theoretical framework for addiction in which the insula represents the interoceptive effects of drug taking, making this information available to conscious awareness, memory and executive functions. A central theme of this framework is that a primary goal for the addicted individual is to obtain the effects of the drug use ritual upon the body, and representations of this goal in interoceptive terms by the insula contribute to how addicted individuals feel, remember, and decide about taking drugs. This makes drug addiction like naturally motivated behaviors, such as eating and sex, for which an embodied ritual is the primary goal.

Varenicline's effects on acute smoking behavior and reward and their association with subsequent abstinence

RATIONALE

Varenicline may aid smoking cessation by attenuating smoking behavior and reward. We compared the effects of varenicline versus placebo on smoking behavior and reward, assessed both prospectively and retrospectively, and related these effects to subsequent success in a brief simulated quit attempt with medication.

MATERIALS AND METHODS

Smokers (n = 124) with high or low interest in quitting smoking participated in a double-blind crossover study of varenicline versus placebo effects on smoking behavior and reward. In each of two phases, subjects received a week of medication run-up with varenicline (0.5 mg, b.i.d.) or placebo while continuing to smoke, followed the next week by an attempt to quit while on medication. At the end of each run-up week, subjects completed retrospective measures of smoking reward (liking) and number of cigarettes over the prior 24 hrs, and they provided an expired air carbon monoxide (CO) measure. They then completed a prospective session in which they ad lib smoked and rated the rewarding effects of one of their preferred cigarettes while blind to brand.

RESULTS

Varenicline decreased smoking reward significantly in the prospective assessment, but only marginally in the retrospective assessment. Varenicline did not alter smoking behavior prospectively, but did reduce CO and retrospective report of smoking amount. None of these effects of varenicline predicted subsequent days of abstinence due to varenicline.

CONCLUSIONS

During medication run-up, varenicline decreases acute smoking reward and may attenuate smoking behavior, but these effects do not appear to directly predict varenicline's influence on smoking abstinence in a short-term test.

Differences in negative mood-induced smoking reinforcement due to distress tolerance, anxiety sensitivity, and depression history

RATIONALE

Negative mood increases smoking reinforcement and may do so to a greater degree in smokers vulnerable to negative mood dysregulation.

METHODS

Adult smokers (N = 71) without current depression were randomly assigned to one of two smoking conditions (nicotine or denic cigarettes, presented blind) maintained across all sessions. Subjects completed one neutral mood session and four negative mood induction sessions. Negative mood inductions included one each of the following: 1) overnight smoking abstinence, 2) challenging computer task, 3) public speech preparation, 4) watching negative mood slides. In each session, subjects took 4 puffs on their assigned cigarette, rated it for "liking" (reward), and then smoked those cigarettes ad libitum (reinforcement) during continued mood induction. Affect was assessed intermittently before and after smoking. Differences in responses were examined as functions of self-reported history of major depression and levels of distress tolerance and anxiety sensitivity.

RESULTS

Smoking reinforcement, but not reward or negative affect relief, was greater in all sessions in those with a history of depression and greater after overnight abstinence in those with lower distress tolerance. Reward and affect relief, but not reinforcement, were greater during speech preparation among those high in anxiety sensitivity.

CONCLUSIONS

Low distress tolerance may enhance acute smoking reinforcement due to abstinence, while depression history may broadly increase acute smoking reinforcement regardless of mood. Neither smoking reward nor affect help explain these individual differences in smoking reinforcement.

Reinforcing effects of nicotine and non-nicotine components of cigarette smoke

RATIONALE

Nicotine and non-nicotine components of cigarette smoke contribute to its reinforcing effects; however, the specific role of each component in maintaining behavior has not yet been elucidated.

OBJECTIVES

To assess the reinforcing effects of nicotine and non-nicotine components of cigarette smoke by presenting a concurrent choice paradigm in which participants had access to intravenous (IV) nicotine infusions vs. saline (placebo) infusions and puffs from denicotinized ("denic") cigarettes vs. air (sham puffs). We also measured the effects on self-administration of prior satiation with each component.

METHODS

Sixteen smokers participated in seven sessions: 1) a baseline smoking assessment, used to tailor the nicotine dose per infusion; 2) two sessions for training discrimination of IV nicotine vs. saline infusions and denic smoke vs. sham puffs; and 3) four sessions assessing choice behavior after different satiation conditions.

RESULTS

Denic smoke was self-administered more than any other alternative, including IV nicotine. IV nicotine, however, was preferred over IV saline and sham puffs. Preference for denic smoke vs. IV nicotine was inversely correlated with subjective ratings of "comfort" associated with nicotine. Smoke satiation reduced the number of denic puffs taken during choice periods, while prior nicotine administration did not affect puffing behavior. Smoking withdrawal symptoms were alleviated both by nicotine administration and by denic smoke.

CONCLUSIONS

In established smokers, non-nicotine aspects of cigarette smoking have potent reinforcing effects. While current smoking cessation pharmacotherapies primarily address the nicotine component of cigarette addiction, future cessation strategies should also be designed to target non-nicotine factors.

Acute negative affect relief from smoking depends on the affect situation and measure but not on nicotine

BACKGROUND

Smoking acutely relieves negative affect (NA) due to smoking abstinence but may not relieve NA from other sources, such as stressors.

METHODS

Dependent smokers (n = 104) randomly assigned to one of three smoking conditions (nicotine or denicotinized cigarettes, or no smoking) completed four negative mood induction procedures (one per session): 1) overnight smoking abstinence, 2) challenging computer task, 3) public speech preparation, and 4) watching negative mood slides. A fifth session involved a neutral mood control. The two smoking groups took four puffs on their assigned cigarette and then smoked those same cigarettes ad libitum during continued mood induction. All subjects rated their level of NA and positive affect on several measures (Mood Form, Positive and Negative Affect Scale, Stress-Arousal Checklist, and State-Trait Anxiety Inventory-state). They also rated craving and withdrawal.

RESULTS

Negative affect relief from smoking depended on the NA source (i.e., mood induction procedure) and the affect measure. Smoking robustly relieved NA due to abstinence on all four measures but only modestly relieved NA due to the other sources and typically on only some measures. Smoking's effects on positive affect and withdrawal were similar to effects on NA, but relief of craving depended less on NA source. Smoking reinforcement only partly matched the pattern of NA relief. Few responses differed between the nicotine and denicotinized smoking groups.

CONCLUSIONS

Acute NA relief from smoking depends on the situation and the affect measure used but may not depend on nicotine intake. These results challenge the common assumption that smoking, and nicotine in particular, broadly alleviates NA.

The effects of nicotine, denicotinized tobacco, and nicotine-containing tobacco on cigarette craving, withdrawal, and self-administration in male and female smokers

The effects of the acute administration of nicotine [through nicotine inhalers (NI) and placebo inhalers (PI)], nicotine-containing tobacco (NT), and denicotinized tobacco (DT), on smokers' subjective responses and motivation to smoke were examined in 22 smokers (12 male, 10 female; 11 low dependent, 11 high dependent). During four randomized blinded sessions, participants self-administered NI, PI, NT, or DT, and assessed their effects using Visual Analogue Scales and the Brief Questionnaire of Smoking Urges. They could then self-administer their preferred brand of cigarettes using a progressive ratio task. NT and DT were each associated with increased satisfaction and relaxation as well as decreased craving relative to the inhalers and NT increased ratings of stimulation relative to each of the other products. Both NT and DT delayed the onset of preferred tobacco self-administration relative to NI and PI but only NT reduced the total amount self-administered. Sex differences were evident in the effects of DT on withdrawal-related cravings with women experiencing greater DT-induced craving relief than men. Findings suggest that DT is effective in acutely reducing many smoking abstinence symptoms, especially in women, but a combination of nicotine and non-nicotine tobacco ingredients may be necessary to suppress smoking behavior.

Effects of sensory and behavioral substitutes following an experimentally induced stressor among abstinent smokeless tobacco users

Despite the well-known health risks associated with smokeless tobacco use, much is unresolved with respect to effective treatment for use of this substance. The present study examined the impact of a nicotine-free smokeless tobacco substitute and confectionary chewing gum on craving, withdrawal, and anxiety among 24 smokeless tobacco users following 24 hours of nicotine abstinence and a laboratory stressor. Although chewing gum did not impact withdrawal, craving, or anxiety compared to a no-product control condition, smokeless tobacco substitute administration resulted in a reduction of withdrawal and craving levels compared to the control condition following 24 hours of abstinence. Furthermore, significantly lower levels of craving and withdrawal were observed in both smokeless tobacco and smokeless tobacco substitute conditions compared to the control condition following the stressor. Results indicate that although general oral stimulation (eg, chewing gum) was not effective in reducing symptoms related to nicotine withdrawal, smokeless tobacco substitute use appears to be helpful in reducing withdrawal levels post-stressor. These data suggest that use of a smokeless tobacco substitute may be an effective aid in helping individuals wishing to quit, especially when managing stressors. (Am J Addict 2010;00:1-8).

Abuse liability assessment of tobacco products including potential reduced exposure products

The harm produced by tobacco products is a result of frequent use of a highly toxic product. Reducing the adverse public health impact of tobacco products might be most effectively achieved by reducing the likelihood of their use and the toxicity of the products. Products that retain some characteristics of cigarettes but have been altered with the intention of reducing toxicity have been referred to as modified risk tobacco products or potential reduced exposure products (MRTP/PREP). Evaluation of their content, emission, and toxicity is discussed in other articles in this special issue. Here, we discuss the methodology that has been used to examine the likelihood of abuse or addiction. Abuse liability assessment (ALA) methodology has been used by the Food and Drug Administration (FDA) and other drug regulatory agencies world-wide for decades to assess the risks posed by a wide variety of pharmacologically active substances. ALA is routinely required among other evaluations of safety during the pre-market assessment of new drugs, and is continually adapted to meet the challenges posed by new drug classes and drug formulations. In the 2009 law giving FDA regulation over tobacco products, FDA is now required to evaluate new tobacco products including MRTP/PREPs to determine their risk for abuse and toxicity at the population level. This article describes the traditional tools and methods of ALA that can be used to evaluate new tobacco and nicotine products including MRTP/PREPs. Such ALA data could contribute to the scientific foundation on which future public policy decisions are based.

Measures for assessing subjective effects of potential reduced-exposure products

Potential reduced-exposure products (PREP) may reduce toxicant exposure and thereby may possibly reduce health risks associated with conventional tobacco use. However, lessened health risk to the individual or harm to the population through the use of PREPs is unknown. Research is being conducted to evaluate the possible health effects associated with PREP use. As part of this evaluation, it is critical to provide sound measures of subjective responses to PREPs to determine the use and the abuse potential of a product, that is, the likelihood that the product will lead to addiction. The goal of this paper is to conduct a systematic review of scales that have been used to measure the subjective responses to PREPs and examine their characteristics. In this article, scales are identified and the items on the scales are described. Scales are also examined to determine whether they are sensitive in testing PREPs. Furthermore, scales to assess PREPs are recommended to investigators. Where no scales exist, items that may be critical for the development and validation of new scales are identified.

Prolonged exposure to denicotinized cigarettes with or without transdermal nicotine

Sensorimotor smoking stimuli are important determinants of cigarette use. The present study aimed to determine whether denicotinized cigarettes lose their reinforcing and/or subjective effects over a 9-day outpatient period when they are smoked with or without concurrent transdermal nicotine. After a preferred brand baseline, 68 participants were randomized into one of four conditions based on the dose (mg) of transdermal nicotine and the type of cigarettes (dose/cigarette): 0/nicotine, 0/denicotinized, 7/denicotinized, and 21/denicotinized. Under placebo patch conditions, participants smoked a similar number of nicotine and denicotinized cigarettes and no group differences emerged over repeated testing. The total volume of smoke inhaled was lower in the denicotinized group, although this decrease dissipated over time. Denicotinized cigarettes were rated as having low positive and high negative subjective effects. Compared to placebo, transdermal nicotine decreased the number of denicotinized cigarette smoked, produced a lasting decrease in the total volume of denicotinized cigarette smoke inhaled, but had little effect on the subjective effects of denicotinized cigarettes. Transdermal nicotine attenuated withdrawal during initial smoking abstinence; however, once participants were allowed to smoke withdrawal symptoms were relatively low regardless of patch condition. The persistent use of denicotinized cigarettes may result from the presence of nicotine withdrawal and/or the degree to which smoking becomes somewhat independent of the outcome of the behavior (i.e., habit learning). Additional studies would be useful to determine what factors drive continued use of denicotinized cigarettes, whether their use subsides as withdrawal dissipates, and whether they address motives for smoking distinct from current pharmacotherapy.

Sex differences in nicotine action

Accumulating evidence suggests that the antecedents, consequences, and mechanisms of drug abuse and dependence are not identical in males and females and that gender may be an important variable in treatment and prevention. Although there has been a decline in smoking prevalence in developed countries, females are less successful in quitting. Tobacco use is accepted to be a form of addiction, which manifests sex differences. There is also evidence for sex differences in the central effects of nicotine in laboratory animals. Although social factors impact smoking substantially in humans, findings from nonhuman subjects in controlled experiments provide support that sex differences in nicotine/tobacco addiction have a biological basis. Differences in the pharmacokinetic properties of nicotine or the effect of gonadal hormones may underlie some but not all sex differences observed. Laboratory-based information is very important in developing treatment strategies. Literature findings suggest that including sex as a factor in nicotine/tobacco-related studies will improve our success rates in individually tailored smoking cessation programs.

Dopamine and opioid gene variants are associated with increased smoking reward and reinforcement owing to negative mood

Negative mood increases smoking reinforcement and risk of relapse. We explored associations of gene variants in the dopamine, opioid, and serotonin pathways with smoking reward ('liking') and reinforcement (latency to first puff and total puffs) as a function of negative mood and expected versus actual nicotine content of the cigarette. Smokers of European ancestry (n=72) were randomized to one of four groups in a 2x2 balanced placebo design, corresponding with manipulation of actual (0.6 vs. 0.05 mg) and expected (told nicotine and told denicotinized) nicotine 'dose' in cigarettes during each of two sessions (negative vs. positive mood induction). Following mood induction and expectancy instructions, they sampled and rated the assigned cigarette, and then smoked additional cigarettes ad lib during continued mood induction. The increase in smoking amount owing to negative mood was associated with: dopamine D2 receptor (DRD2) C957T (CC>TT or CT), SLC6A3 (presence of 9 repeat>absence of 9), and among those given a nicotine cigarette, DRD4 (presence of 7 repeat>absence of 7) and DRD2/ANKK1 TaqIA (TT or CT>CC). SLC6A3, and DRD2/ANKK1 TaqIA were also associated with smoking reward and smoking latency. OPRM1 (AA>AG or GG) was associated with smoking reward, but SLC6A4 variable number tandem repeat was unrelated to any of these measures. These results warrant replication but provide the first evidence for genetic associations with the acute increase in smoking reward and reinforcement owing to negative mood.