Smoking abstinence and neurocognition: implications for cessation and relapse

Effects of acute smoking abstinence among people with schizophrenia: A systematic review and meta-analysis of laboratory studies

BACKGROUND

Smoking rates in schizophrenia are exceptionally high; however, cessation rates remain low with limited research on effective interventions. A critical component of intervention development is identifying the effects of abstinence that are most salient and therefore may contribute to lapse and relapse.

OBJECTIVES

We conducted a systematic review and meta-analysis of controlled laboratory studies investigating acute smoking abstinence effects among people with schizophrenia and schizoaffective disorder.

METHODS

This review is reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. OVID (MEDLINE, EMBASE, PsycINFO) and PubMed databases were searched from inception until November 2023.

RESULTS

We identified (k = 16) articles meeting inclusion criteria; all assessed smoking abstinence (ranging 2-120 h). Acute abstinence resulted in large increases in reward-oriented craving and moderate increases in relief-oriented craving; these effects were greater in studies with longer abstinence duration (high certainty). We also observed significant increases in negative affect and global withdrawal symptoms, as well as memory disruption (moderate certainty). Qualitative synthesis suggests restlessness, irritability, anxiety, and visuospatial working memory may be additionally impacted. Findings with respect to negative symptoms and movement were mixed.

CONCLUSIONS

Reward-oriented craving may constitute a key target of smoking cessation interventions for people with schizophrenia. In addition, identification of pharmacological and psychosocial interventions that address abstinence-induced changes in relief-oriented craving, memory, negative affect, restlessness, irritability, and anxiety may strengthen treatment outcomes.

Sex differences in the prospective association of excessively long reaction times and hazardous cannabis use at six months

Objective

The neurocognitive risk mechanisms predicting divergent outcomes likely differ between men and women who use cannabis recreationally. Increasingly, the use of descriptive distributions including the ex-Gaussian has been applied to draw stronger inferences about neurocognitive health in clinical populations. The current project examines whether the long tail of reaction times (RTs) in a distribution, as characterized by the ex-Gaussian parameter tau which may represent difficulty with the regulation of arousal, predicts problematic cannabis use 6 months later in those who use cannabis recreationally, and whether sex moderates these prospective associations.

Method

Young adults (ages 18-30, mean age 20.5 years, N =159, 57.2% women, 69.2% Caucasian) who recreationally used cannabis either occasionally (at least once per month) or frequently (three times or more per week) completed the Stroop Color-Word Task at baseline. Ex-Gaussian parameter tau was estimated for each participant. Self-report of hazardous cannabis use (CUDIT-R) and dysregulation of negative (DERS) and positive emotions (DERS-Positive) were obtained at baseline and 6-month follow-up.

Results

For those with larger tau at baseline, being a man (but not a woman) was associated with increased difficulty regulating positive emotions concurrently (b = -0.01, F (1,159) = 5.48, p = 0.02), and with hazardous cannabis use six months later (b = -0.007, F (1,159) = 4.42, p = 0.037) after controlling for baseline hazardous cannabis use.

Conclusions

Excessively long RTs during cognitive performance may help characterize men at risk for increased hazardous use, which contributes to understanding between-sex heterogeneity in pathways towards cannabis use disorders.

The interaction of oxytocin and nicotine addiction on psychosocial stress: an fMRI study

The anxiolytic effect of oxytocin (OXT) on psychosocial stress has been well documented, but the effectiveness under the interference of other factors still requires in-depth research. Previous studies have shown that nicotine addiction interacts with OXT on psychosocial stress on the behavioral level. However, the underlying neural mechanism of interaction between OXT and nicotine addiction on psychosocial stress has not been examined, and we conducted two experiments to reveal it. Firstly, after intranasal administration of randomized OXT or placebo (saline), a group of healthy participants (n = 27) and a group of smokers (n = 26) completed the Montreal Imaging Stress Task (MIST) in an MRI scanner. Secondly, a group of smokers (n = 22) was recruited to complete a transcranial direct current stimulation (tDCS) experiment, in which anodal tDCS was applied on subjects' anterior right superior temporal gyrus (rSTG). In both experiment, subjective stress ratings, salivary cortisol samples and the amount of daily cigarette consumption were obtained from each participant. Analysis of variance were applied on both behavioral and neural data to examine the effects of OXT and nicotine addiction, and correlation analysis were used to examine relationships between neural and behavioral data. In first fMRI experiment, analysis of variance (ANOVA) revealed an interaction of OXT and nicotine addiction on subjective stress. In smokers, OXT failed to suppress the elevation of subjective stress and craving ratings after psychosocial stress. A voxel-wise ANOVA of fMRI data identified an interaction between OXT and nicotine addiction in anterior rSTG, and its functional connectivity with right middle frontal gyrus. Correlations between this functional connectivity and subjective psychosocial stress were also found abnormal in smokers. In second tDCS experiment, we found that under tDCS, OXT successfully suppressed the elevation of subjective stress and craving ratings after stress. In summary, we found that nicotine addiction blocked OXT's anxiolytic on psychosocial stress, which was related to abnormalities in anterior rSTG. By applying anodal tDCS on anterior rSTG, OXT's anxiolytic effect was restored in smokers. These findings will support further development on oxytocin's intervention of psychosocial stress in nicotine addiction, and provides essential information for indicating OXT's effectiveness.

Association of sun-seeking behaviors with indoor tanning behavior in US white females during high school/college in Nurses' Health Study II

BACKGROUND

Frequent exposure to ultraviolet light has more detrimental and longer-term effects on the skin in early life than in adulthood. Teenagers with strong sun-seeking behaviors may be more likely to use an indoor tanning bed than those who seek less sun. We aimed to examine associations between sun-seeking behaviors and indoor tanning behavior during high school/college in US females.

METHODS

In this cross-sectional study, we used data from The Nurses' Health Study II, a large prospective cohort of US female nurses. We included a total of 81,746 white females who provided responses on the average annual frequency of indoor tanning during high school/college. Our study exposures were number of times/week spent outdoors in a swimsuit and percentage of time wearing sunscreen at the pool/beach as a teenager, weekly hours spent outdoors in direct sunlight during the daytime during high school/college, and number of severe sunburns that blistered between ages 15-20 years. The main outcome was annual frequency of indoor tanning bed usage during high school/college.

RESULTS

In multivariable-adjusted logistic regression, we demonstrated positive associations between sun-seeking behaviors and indoor tanning use. Specifically, teenagers who spent 7 times/week outdoors in a swimsuit (adjusted odds ratio [aOR], 95% confidence interval [CI] for daily vs. <1/week: 2.68, 1.76-4.09) were more likely to use indoor tanning beds ≥ 12 times/year. Teenagers with ≥ 10 sunburns (aOR, 95% CI for ≥ 10 vs. never: 2.18, 1.53-3.10) were more likely to use indoor tanning beds ≥ 12 times/year. Also, teenagers/undergraduates who spent ≥ 5 h/week outdoors in direct sunlight (aOR, 95% CI for ≥ 5 h/week vs. <1 h/week: 2.18, 1.39-3.44) were more likely to use indoor tanning ≥ 12 times/year. However, there was not a significant association between average usage of sunscreen at the pool/beach and average usage of indoor tanning beds. Multivariable-adjusted linear regression models also showed similar results.

CONCLUSIONS

Teenagers who spent more time outdoors in a swimsuit/direct sunlight or got more sunburns tended to use indoor tanning more frequently. These findings provide evidence that teenagers with stronger sun-seeking behaviors may have more exposure to artificial ultraviolet radiation as well.

Association of sun-seeking behaviors with indoor tanning habit in US females

Background

Frequent exposure to ultraviolet light in early life has more detrimental and long-term effects on skin than in adulthood. Teenagers with strong sun-seeking behaviors may be more likely to use an indoor tanning bed than those who seek less sun, probably due to addictiveness of ultraviolet exposure. We aimed to examine associations between sun exposure behaviors and average annual indoor tanning usage frequency during high school/college in US females.

Methods

In this cross-sectional study, we used data from The Nurses' Health Study II, a large prospective cohort of US female nurses. We included a total of 81,746 white females who answered the average annual frequency of indoor tanning during high school/college. Our study exposures were average weekly time spent outdoors in a swimsuit and average percentage of time of wearing sunscreen at the pool or beach during their teenage years, average weekly hours spent outdoors in direct sunlight in daytime during high school/college, and the number of severe sunburns which blistered between ages 15-20. Main outcomes was average annual frequency of indoor tanning bed usage during high school/college.

Results

In multivariable-adjusted logistic regression, we demonstrated positive associations between the sun exposure behaviors and the indoor tanning habit. Specifically, teenagers who spent daily outdoors in a swimsuit (adjusted odds ratio [aOR], 95% confidence interval [CI] for daily vs. <1/week: 2.68, 1.76-4.09) or who had ≥ 10 sunburns that blistered (aOR, 95% CI for ≥ 10 vs. never: 2.18, 1.53-3.10) were more likely to use indoor tanning beds ≥ 12 times/year. Also, teenagers/undergraduates who spent ≥ 5hours/week outdoors in direct sunlight during daytime used indoor tanning ≥ 12 times/year (aOR, 95% CI: 2.18, 1.39-3.44) than those who spent < 1/week. However, there was not a significant association between average uses of sunscreen at the pool/beach and indoor tanning bed. Multivariable-adjusted linear regression models also showed similar results.

Conclusions

Teenagers who spent more time outdoors or got more sunburns tended to use indoor tanning more frequently. These findings provide evidence that teenagers with strong sun-seeking behaviors may have excessive exposure to artificial ultraviolet radiation as well.

The Role of Attentional Networks in Smoking Behavior Among Young Adults: Specific Contribution of Executive Control

INTRODUCTION

The exploration of cognitive impairments associated with tobacco use disorder has expanded during the last decades, centrally showing working memory and executive deficits among smokers. Despite their critical role in everyday life and in the smoking cessation process, attentional abilities have seldom been explored. Previous studies yielded discordant results, and the involvement of attentional deficits in smoking habits remains unclear.

AIMS AND METHODS

Capitalizing on the Attention Network Test, a theory-grounded task allowing the simultaneous but distinct evaluation of three attentional networks (alerting, orienting, executive control), we explored attentional abilities in three groups of 25 college students (nonsmokers, light smokers, heavy smokers), matched for demographic and psychopathological characteristics.

RESULTS

While light smokers did not present any deficit compared with nonsmokers, heavy smokers showed a specific impairment of the executive control subcomponent of attention, contrasting with preserved alerting and orienting attentional abilities. The executive control deficit was not related to current craving or to smoking duration.

CONCLUSIONS

Beyond the already explored memory and executive deficits, tobacco use disorder is associated with attentional impairments, characterized by a reduced ability to focus attentional resources on pertinent stimuli and resist to distractors interference. Given the assumed role of attentional impairments in smoking, our findings suggest that a critical step in future translational iterations is to develop neuropsychological rehabilitation programs tapping into the executive network of attention among smokers.

IMPLICATIONS

This study clarifies the presence and extent of attentional impairments in tobacco use disorder. We measured three attention networks (alerting, orienting, executive control) in light smokers, heavy smokers and matched healthy controls through a theory-grounded task (Attention Network Test). Heavy smokers (but not light ones) present a specific deficit for the executive control of attention. This deficit, uncorrelated with psychopathological comorbidities or current craving, appears directly related to smoking. Given the currently scattered literature on this topic, attentional processes deserve a thorough audit in tobacco use disorder, notably to develop specific neurocognitive rehabilitation.

Not all smokers are alike: the hidden cost of sustained attention during nicotine abstinence

Nicotine Withdrawal Syndrome (NWS)-associated cognitive deficits are notably heterogeneous, suggesting underlying endophenotypic variance. However, parsing this variance in smokers has remained challenging. In this study, we identified smoker subgroups based on response accuracy during a Parametric Flanker Task (PFT) and then characterized distinct neuroimaging endophenotypes using a nicotine state manipulation. Smokers completed the PFT in two fMRI sessions (nicotine sated, abstinent). Based on response accuracy in the stressful, high cognitive demand PFT condition, smokers split into high (HTP, n = 21) and low task performer (LTP, n = 24) subgroups. Behaviorally, HTPs showed greater response accuracy (88.68% ± 5.19 SD) vs. LTPs (51.04% ± 4.72 SD), independent of nicotine state, and greater vulnerability to abstinence-induced errors of omission (EOm, p = 0.01). Neurobiologically, HTPs showed greater BOLD responses in attentional control brain regions, including bilateral insula, dorsal ACC, and frontoparietal Cx for the [correct responses (-) errors of commission] PFT contrast in both states. A whole-brain functional connectivity (FC) analysis with these subgroup-derived regions as seeds identified two circuits: Precentral Cx↔Insula and Insula↔Occipital Cx, with abstinence-induced FC strength increases seen only in HTPs. Finally, abstinence-induced FC and behavior (EOm) differences were positively correlated for HTPs in a Precentral Cx↔Orbitofrontal cortical circuit. In sum, only the HTP subgroup demonstrated sustained attention deficits following 48-hr nicotine abstinence, a stressor in dependent smokers. Unpacking underlying smoker heterogeneity with this 'dual (task and abstinence) stressor' approach revealed discrete smoker subgroups with differential attentional deficits to withdrawal that could be novel pharmacological/behavioral targets for therapeutic interventions to improve cessation outcomes.

Cognition, Aryl Hydrocarbon Receptor Repressor Methylation, and Abstinence Duration-Associated Multimodal Brain Networks in Smoking and Long-Term Smoking Cessation

Cigarette smoking and smoking cessation are associated with changes in cognition and DNA methylation; however, the neurobiological correlates of these effects have not been fully elucidated, especially in long-term cessation. Cognitive performance, percent methylation of the aryl hydrocarbon receptor repressor (AHRR) gene, and abstinence duration were used as references to supervise a multimodal fusion analysis of functional, structural, and diffusion magnetic resonance imaging (MRI) data, in order to identify associated brain networks in smokers and ex-smokers. Correlations among these networks and with smoking-related measures were performed. Cognition-, methylation-, and abstinence duration-associated networks discriminated between smokers and ex-smokers and correlated with differences in fractional amplitude of low frequency fluctuations (fALFF) values, gray matter volume (GMV), and fractional anisotropy (FA) values. Long-term smoking cessation was associated with more accurate cognitive performance, as well as lower fALFF and more GMV in the hippocampus complex. The methylation- and abstinence duration-associated networks positively correlated with smoking-related measures of abstinence duration and percent methylation, respectively, suggesting they are complementary measures. This analysis revealed structural and functional co-alterations linked to smoking abstinence and cognitive performance in brain regions including the insula, frontal gyri, and lingual gyri. Furthermore, AHRR methylation, a promising epigenetic biomarker of smoking recency, may provide an important complement to self-reported abstinence duration.

Associations Between Smoking Abstinence, Inhibitory Control, and Smoking Behavior: An fMRI Study

Nicotine addiction is associated with dysregulated inhibitory control (IC), mediated by corticothalamic circuitry including the right inferior frontal gyrus (rIFG). Among sated smokers, worse IC task performance and greater IC-related rIFG activity have been shown to be associated with greater relapse vulnerability. The present study investigated the effects of smoking abstinence on associations between IC task performance, rIFG activation, and smoking behavior. Smokers (N = 26, 15 female) completed an IC task (Go/Go/No-go) during fMRI scanning followed by a laboratory-based smoking relapse analog task (SRT) on two visits: once when sated and once following 24 h of smoking abstinence. During the SRT, smokers were provided with monetary rewards for incrementally delaying smoking. A significant main effect of No-go accuracy on latency to smoke during the SRT was observed when collapsing across smoking states (abstinent vs. sated). Similarly, a significant main effect of IC-related activation in rIFG on SRT performance was observed across states. The main effect of state, however, was non-significant in both of these models. Furthermore, the interaction between smoking state and No-go accuracy on SRT performance was non-significant, indicating a similar relationship between IC and lapse vulnerability under both sated and abstinent conditions. The state X rIFG activation interaction on SRT performance was likewise non-significant. Post-hoc whole brain analyses indicated that abstinence resulted in greater IC-related activity in the right middle frontal gyrus (MFG) and insula. Activation during IC in these regions was significantly associated with decreased No-go accuracy. Moreover, greater abstinence induced activity in right MFG during IC was associated with smoking sooner on the SRT. These findings are bolstered by the extant literature on the effects of nicotine on executive function and also contribute novel insights on how individual differences in behavioral and neuroimaging measures of IC may influence relapse propensity independent of smoking state.

Menthol Cigarettes, Tobacco Dependence, and Smoking Persistence: The Need to Examine Enhanced Cognitive Functioning as a Neuropsychological Mechanism

INTRODUCTION

Despite the overall decline in the prevalence of cigarette use in the United States, menthol cigarette use among smokers is rising, and evidence shows that it may lead to more detrimental effects on public health than regular cigarette use. One of the mechanisms by which nicotine sustains tobacco use and dependence is due to its cognitive enhancing properties, and basic science literature suggests that menthol may also enhance nicotine's acute effect on cognition.

AIMS AND METHODS

The purpose of this review is to suggest that the cognitive enhancing effects of menthol may be a potentially important neuropsychological mechanism that has yet to be examined. In this narrative review, we provide an overview of basic science studies examining neurobiological and cognitive effects of menthol and menthol cigarette smoking. We also review studies examining menthol essential oils among humans that indicate menthol alone has acute cognitive enhancing properties. Finally, we present factors influencing the rising prevalence of menthol cigarette use among smokers and the importance of this gap in the literature to improve public health and smoking cessation treatment.

CONCLUSIONS

Despite the compelling evidence for menthol's acute cognitive enhancing and reinforcing effects, this mechanism for sustaining tobacco dependence and cigarette use has yet to be examined and validated among humans. On the basis of the basic science evidence for menthol's neurobiological effects on nicotinic receptors and neurotransmitters, perhaps clarifying menthol's effect on cognitive performance can help to elucidate the complicated literature examining menthol and tobacco dependence.

IMPLICATIONS

Menthol cigarette use has continued to be a topic of debate among researchers and policy makers, because of its implications for understanding menthol's contribution to nicotine dependence and smoking persistence, as well as its continued use as a prevalent flavoring in tobacco and nicotine products in the United States and internationally. As international tobacco regulation policies have begun to target menthol cigarettes, research studies need to examine how flavoring additives, specifically menthol, may acutely influence neurobiological and cognitive functioning as a potential mechanism of sustained smoking behavior to develop more effective treatments.

The effect of varenicline on mood and cognition in smokers with HIV

RATIONALE

Barriers to smoking cessation, including negative affect and cognitive dysfunction, may contribute to high smoking rates among people living with HIV/AIDS (PLWH). Varenicline may help PLWH quit smoking by improving mood and cognition, yet this has not been explored.

OBJECTIVES

The goal of this study was to evaluate the effect of varenicline on mood and cognition among PLWH enrolled in a smoking cessation clinical trial.

METHODS

In this secondary analysis of a varenicline trial (NCT01710137), we assessed mood (depression, anxiety) and cognition (attention, working memory) at weeks 0 (baseline), 1, 3, and 12 (end-of-treatment, EOT). Primary outcomes were changes in mood and cognition from baseline to EOT. Secondarily, mood and cognition were evaluated as predictors of biochemically confirmed 7-day point-prevalence abstinence at EOT.

RESULTS

Overall, 173 subjects (87 varenicline, 86 placebo) were included. At EOT, varenicline reduced anxiety (P < 0.001), vs. placebo (P = 0.31; interaction P = 0.05). Across both treatment arms, reductions in anxiety from baseline to EOT were associated with a higher likelihood of abstinence (OR = 1.3, 95% CI 1.1 to 1.6, P = 0.01). There were no significant treatment by time interactions for cognition or depression.

CONCLUSIONS

These data suggest that varenicline operates, at least in part, by reducing anxiety. Anxiety should be an intervention target for smokers with HIV interested in quitting.

Transcranial Direct Current Stimulation Applied to the Dorsolateral and Ventromedial Prefrontal Cortices in Smokers Modifies Cognitive Circuits Implicated in the Nicotine Withdrawal Syndrome

BACKGROUND

The nicotine withdrawal syndrome remains a major impediment to smoking cessation. Cognitive and affective disturbances are associated with altered connectivity within and between the executive control network, default mode network (DMN), and salience network. We hypothesized that functional activity in cognitive control networks, and downstream amygdala circuits, would be modified by application of transcranial direct current stimulation (tDCS) to the left (L) dorsolateral prefrontal cortex (dlPFC, executive control network) and right (R) ventromedial prefrontal cortex (vmPFC, DMN).

METHODS

A total of 15 smokers (7 women) and 28 matched nonsmokers (14 women) participated in a randomized, sham-controlled, double-blind, exploratory crossover study of 3 tDCS conditions: anodal-(L)dlPFC/cathodal-(R)vmPFC, reversed polarity, and sham. Cognitive tasks probed withdrawal-related constructs (error monitoring, working memory, amygdalar reactivity), while simultaneous functional magnetic resonance imaging measured brain activity. We assessed tDCS impact on trait (nonsmokers vs. sated smokers) and state (sated vs. abstinent) smoking aspects.

RESULTS

Single-session, anodal-(L)dlPFC/cathodal-(R)vmPFC tDCS enhanced deactivation of DMN nodes during the working memory task and strengthened anterior cingulate cortex activity during the error-monitoring task. Smokers were more responsive to tDCS-induced DMN deactivation when sated (vs. withdrawn) and displayed greater cingulate activity during error monitoring than nonsmokers. Nicotine withdrawal reduced task engagement and attention and reduced suppression of DMN nodes.

CONCLUSIONS

Cognitive circuit dysregulation associated with nicotine withdrawal may be modifiable by anodal tDCS applied to L-dlPFC and cathodal tDCS applied to R-vmPFC. tDCS may have stronger effects as a complement to existing therapies, such as nicotine replacement, owing to possible enhanced plasticity in the sated state.

Lack of effect of transcranial direct current stimulation (tDCS) on short-term smoking cessation: Results of a randomized, sham-controlled clinical trial

BACKGROUND

Transcranial direct current stimulation (tDCS) has been shown to improve measures of executive cognitive function and reduce cigarette consumption. Studies conducted to date have been small, and the results are mixed.

METHODS

This randomized, double-blind, parallel arm clinical trial tested the effects of active anodal tDCS targeted to the left dorsolateral prefrontal cortex (versus sham) on 7-day smoking cessation in 106 treatment-seeking smokers. Participants received three sessions of sham (n = 35), 1 mA (n = 35), or 2 mA (n = 36) tDCS in the context of a validated smoking lapse paradigm then received brief smoking cessation counseling and completed a monitored quit attempt. The primary outcome was total number of days of abstinence confirmed via exhaled carbon monoxide.

RESULTS

During the quit period, there were no effects of dose group on days of abstinence (sham, M (SD): 2.5 days (±2.5); 1 mA: 2.5 days (±2.5); 2 mA: 2.4 days (±2.3); β = -0.08; p = 0.76) or on change in daily smoking rate (sham, M (SD): 12.6 CPD (±4.8); 1 mA: -11.8 CPD (±4.4); 2 mA: -11.7 CPD (±5.3); β = 0.42, p = 0.49), nor were there effects of dose group on latency to smoke or number of cigarettes smoked during the smoking lapse paradigm. Side effects of tDCS were generally mild (<5 out of 10), and participants were not able to distinguish between active and sham treatment.

CONCLUSIONS

These results do not support the efficacy of tDCS targeted to the left dorsolateral prefrontal cortex (DLPFC) for smoking cessation.

A cognitive model-based approach to testing mechanistic explanations for neuropsychological decrements during tobacco abstinence

RATIONALE

Cigarette smokers often experience cognitive decrements during abstinence from tobacco, and these decrements may have clinical relevance in the context of smoking cessation interventions. However, limitations of the behavioral summary statistics used to measure cognitive effects of abstinence, response times (RT) and accuracy rates, may restrict the field's ability to identify robust abstinence effects on task performance and test mechanistic hypotheses about the etiology of these cognitive changes.

OBJECTIVES

The current study explored whether a measurement approach based on mathematical models of cognition, which make the cognitive mechanisms necessary to perform choice RT tasks explicit, would be able to address these limitations.

METHODS

The linear ballistic accumulator model (LBA: Brown and Heathcote, Cogn Psychol 57(3):153-178, 2008) was fit to an existing data set from a study that evaluated the impact of overnight abstinence on flanker task performance.

RESULTS

The model-based analysis provided evidence that smokers' rates of mind wandering increased during abstinence, and was able to index this effect while controlling for participants' strategy changes that were related to the specific experimental paradigm used.

CONCLUSION

Mind wandering is a putative explanation for cognitive withdrawal symptoms during smoking cessation and may be indexed using the LBA. More broadly, the use of formal model-based analyses in future research on this topic has the potential to allow for strong and specific tests of mechanistic explanations for these symptoms.

Phase IIb Trial of an α7 Nicotinic Receptor Partial Agonist With and Without Nicotine Patch for Withdrawal-Associated Cognitive Deficits and Tobacco Abstinence

PURPOSE/BACKGROUND

The objective of this study was to determine whether a novel α7 nicotinic acetylcholine receptor partial agonist improves cognition during nicotine withdrawal and improves abstinence rates. To do so, the effect of the α7 nicotinic acetylcholine receptor partial agonist, encenicline, on cognition and abstinence was evaluated when given as monotherapy and when combined with transdermal nicotine patch (nicotine replacement therapy [NRT]).

METHODS

Adult daily smokers, n = 160, who were motivated to quit smoking completed cognitive testing at satiated baseline and after overnight abstinence and then were randomized to receive a 12-week trial of encenicline 1 mg twice daily or identical placebo the day of the overnight abstinent cognitive testing. In the first 6 weeks of the 12-week encenicline administration, participants were also randomized to 6 weeks of NRT patch or placebo patch. Primary outcomes were cognition during abstinence and 7-day point-prevalence abstinence at week 12.

RESULTS

No beneficial effects of encenicline were observed on cognition or abstinence when compared with placebo or when combined with NRT compared with placebo capsule + NRT. Of the 4 conditions, abstinence rates were lowest among those assigned to encenicline alone.

CONCLUSIONS

Beneficial effects of NRT were observed on cognitive and abstinence outcomes when combined with encenicline compared with encenicline plus placebo patch. Addition of NRT to encenicline improved odds of abstinence approximately 3-fold compared with encenicline plus placebo patch. We conclude that encenicline, 1 mg/d, did not improve abstinence-associated cognitive impairment or abstinence rates as monotherapy or adjunctive therapy to NRT patch.

Neuregulin 3 Signaling Mediates Nicotine-Dependent Synaptic Plasticity in the Orbitofrontal Cortex and Cognition

Neuregulin 3 (NRG3) and ErbB4 have been linked to nicotine addiction; however, the neuronal mechanisms and behavioral consequences of NRG3-ErbB4 sensitivity to nicotine remain elusive. Recent literature suggests that relapse to smoking is due to a lack of impulsive control, which is thought to be due to altered functioning within the orbitofrontal cortex (OFC). Therefore, we examined circuitry changes within this structure following nicotine application. We report that nicotine controls synaptic plasticity in the OFC through NRG3/ErbB4-dependent regulation of GABAergic inhibition. We observed that both nicotine and NRG3 facilitated the conversion of long-term potentiation into long-term depression at cortical layer 3/5 synapses. Induction of long-term depression by nicotine relied on nicotinic receptor activation and key regulators of NRG3 signaling: (1) release of intracellular calcium, (2) activation of the BACE1 beta-secretase, and (3) ErbB4 receptor activation. Nicotine-induced synaptic plasticity was also associated with accumulation of intracellular GABA and was completely blocked by GABAA/GABAB antagonists. To test whether these mechanisms underlie OFC-dependent behavior, we evaluated the effects of nicotine in the go/no-go task. Nicotine-impaired stimulus discrimination in this task was rescued by pharmacologic disruption of the NRG3 receptor, ErbB4. Altogether, our data indicate that nicotine-induced synaptic plasticity in the OFC and cognitive changes depend on NRG3-ErbB4 signaling. We propose that nicotine activation of this pathway may contribute to nicotine addiction, particularly in individuals with genetic variation in NRG3.

ADHD, Smoking Withdrawal, and Inhibitory Control: Results of a Neuroimaging Study with Methylphenidate Challenge

Smoking withdrawal negatively impacts inhibitory control, and these effects are greater for smokers with preexisting attention problems, such as attention deficit/hyperactivity disorder (ADHD). The current study preliminarily evaluated changes in inhibitory control-related behavior and brain activation during smoking withdrawal among smokers with ADHD. Moreover, we investigated the role of catecholamine transmission in these changes by examining the effects of 40 mg methylphenidate (MPH) administration. Adult daily smokers with (n=17) and without (n=20) ADHD completed fMRI scanning under each of three conditions: (a) smoking as usual+placebo; (b) 24 h smoking abstinence+placebo and (c) 24 h smoking abstinence+MPH. Scan order was randomized and counterbalanced. Participants completed a modified Go/No-Go task to assess both sustained and transient inhibitory control. Voxelwise analysis of task-related BOLD signal revealed a significant group-by-abstinence interaction in occipital/parietal cortex during sustained inhibition, with greater abstinence-induced decreases in activation observed among ADHD smokers compared with non-ADHD smokers. Changes in behavioral performance during abstinence were associated with changes in activation in regions of occipital and parietal cortex and bilateral insula during sustained inhibition in both groups. MPH administration improved behavioral performance and increased sustained inhibitory control-related activation for both groups. During transient inhibition, MPH increased prefrontal activation for both groups and increased striatal activation only among ADHD smokers. These preliminary findings suggest that abstinence-induced changes in catecholamine transmission in visual attention areas (eg, occipital and superior parietal cortex) may be associated with inhibitory control deficits and contribute to smoking vulnerability among individuals with ADHD.

Nicotine Abstinence Influences the Calculation of Salience in Discrete Insular Circuits

BACKGROUND

Insular subdivisions show distinct patterns of resting-state functional connectivity (rsFC) with specific brain regions, each with different functional significance. Seeds in these subdivisions are employed to characterize the effects of acute nicotine abstinence on rsFC between insula subdivisions and brain networks implicated in addiction and attentional control.

METHODS

In a within-subjects design, resting-state blood oxygen level-dependent data were collected from treatment-seeking smokers (N= 20) following smoking satiety and again following 48 hours of nicotine abstinence. Three right hemisphere insular regions of interest (dorsal, ventral, and posterior) served as seeds for analyses. Indices of both static and dynamic rsFC were obtained and correlated with indices of subjective withdrawal and behavioral performance.

RESULTS

Abstinence-induced physiological, subjective, and cognitive differences were observed. Overall dynamic rsFC was reduced during abstinence, and circuits containing each insular seed showed changes in rsFC as a function of nicotine abstinence. Specifically, dorsal and posterior insular connections to the default mode and salience networks were enhanced, while a previously undescribed ventral insular connection to the executive control network was reduced. Further, static rsFC was significantly correlated with subjective ratings of aversive affect and withdrawal in the modified ventral and posterior insular-seeded circuits.

CONCLUSIONS

As predicted, divergent connections between insula subdivisions and anticorrelated resting brain networks were observed during abstinence. These changes reflect an attentional bias toward aversive affective processing and not directly away from exogenous cognitive processing, suggesting a coordinated modulation of circuits associated with interoceptive and affective processing that instantiates an aversive state during nicotine abstinence.

Brain CYP2B induction can decrease nicotine levels in the brain

Nicotine can be metabolized by the enzyme CYP2B; brain CYP2B is higher in rats and monkeys treated with nicotine, and in human smokers. A 7-day nicotine treatment increased CYP2B expression in rat brain but not liver, and decreased the behavioral response and brain levels (ex vivo) to the CYP2B substrate propofol. However, the effect of CYP2B induction on the time course and levels of circulating brain nicotine in vivo has not been demonstrated. Using brain microdialysis, nicotine levels following a subcutaneous nicotine injection were measured on day one and after a 7-day nicotine treatment. There was a significant time x treatment interaction (p = 0.01); peak nicotine levels (15-45 minutes post-injection) were lower after treatment (p = 0.04) consistent with CYP2B induction. Following a two-week washout period, brain nicotine levels increased to day one levels (p = 0.02), consistent with brain CYP2B levels returning to baseline. Brain pretreatment of the CYP2B inhibitor, C8-xanthate, increased brain nicotine levels acutely and after 7-day nicotine treatment, indicating the alterations in brain nicotine levels were due to changes in brain CYP2B activity. Plasma nicotine levels were not altered for any time or treatment sampled, confirming no effect on peripheral nicotine metabolism. These results demonstrate that chronic nicotine, by increasing brain CYP2B activity, reduces brain nicotine levels, which could alter nicotine's reinforcing effects. Higher brain CYP2B levels in smokers could lower brain nicotine levels; as this induction would occur following continued nicotine exposure it could increase withdrawal symptoms and contribute to sustaining smoking behavior.

Nicotine withdrawal-induced inattention is absent in alpha7 nAChR knockout mice

RATIONALE

Smoking is the leading cause of preventable death in the USA, but quit attempts result in withdrawal-induced cognitive dysfunction and predicts relapse. Greater understanding of the neural mechanism(s) underlying these cognitive deficits is required to develop targeted treatments to aid quit attempts.

OBJECTIVES

We examined nicotine withdrawal-induced inattention in mice lacking the α7 nicotinic acetylcholine receptor (nAChR) using the five-choice continuous performance test (5C-CPT).

METHODS

Mice were trained in the 5C-CPT prior to osmotic minipump implantation containing saline or nicotine. Experiment 1 used 40 mg kg-1 day-1 nicotine treatment and tested C57BL/6 mice 4, 28, and 52 h after pump removal. Experiment 2 used 14 and 40 mg kg-1 day-1 nicotine treatment in α7 nAChR knockout (KO) and wildtype (WT) littermates tested 4 h after pump removal. Subsets of WT mice were killed before and after pump removal to assess changes in receptor expression associated with nicotine administration and withdrawal.

RESULTS

Nicotine withdrawal impaired attention in the 5C-CPT, driven by response inhibition and target detection deficits. The overall attentional deficit was absent in α7 nAChR KO mice despite response disinhibition in these mice. Synaptosomal glutamate mGluR5 and dopamine D4 receptor expression were reduced during chronic nicotine but increased during withdrawal, potentially contributing to cognitive deficits.

CONCLUSIONS

The α7 nAChR may underlie nicotine withdrawal-induced deficits in target detection but is not required for response disinhibition deficits. Alterations to the glutamatergic and dopaminergic pathways may also contribute to withdrawal-induced attentional deficits, providing novel targets to alleviate the cognitive symptoms of withdrawal during quit attempts.

Cigarette smoking and depression comorbidity: systematic review and proposed theoretical model

BACKGROUND AND AIMS

Despite decades of research on co-occurring smoking and depression, cessation rates remain consistently lower for depressed smokers than for smokers in the general population, highlighting the need for theory-driven models of smoking and depression. This paper provides a systematic review with a particular focus upon psychological states that disproportionately motivate smoking in depression, and frame an incentive learning theory account of smoking-depression co-occurrence.

METHODS

We searched PubMed, Scopus, PsychINFO and CINAHL to December 2014, which yielded 852 papers. Using pre-established eligibility criteria, we identified papers focused on clinical issues and motivational mechanisms underlying smoking in established, adult smokers (i.e. maintenance, quit attempts and cessation/relapse) with elevated symptoms of depression. Two reviewers determined independently whether papers met review criteria. We included 297 papers in qualitative synthesis.

RESULTS

Our review identified three primary mechanisms that underlie persistent smoking among depressed smokers: low positive affect, high negative affect and cognitive impairment. We propose a novel application of incentive learning theory which posits that depressed smokers experience greater increases in the expected value of smoking in the face of these three motivational states, which promotes goal-directed choice of smoking behavior over alternative actions.

CONCLUSIONS

The incentive learning theory accounts for current evidence on how depression primes smoking behavior and provides a unique framework for conceptualizing psychological mechanisms of smoking maintenance among depressed smokers. Treatment should focus upon correcting adverse internal states and beliefs about the high value of smoking in those states to improve cessation outcomes for depressed smokers.

Transdiagnostic impairment of cognitive control in mental illness

Intact cognitive control or executive function has characteristic patterns in both behavior and functional neurocircuitry. Functional neuroimaging studies have shown that a frontal-cingulate-parietal-insular (i.e., "multiple demand") network forms a common functional substrate undergirding successful adaptation to diverse cognitive processing demands. Separate work on intact neurocognitive performance implicates a higher order factor that largely explains performance across domains and may reflect trait cognitive control capacity. In the current review we highlight findings from respective psychiatric disorders (i.e., psychotic, bipolar and unipolar depressive, anxiety, and substance use disorders) suggesting that cognitive control perturbations amidst psychopathology are most pronounced within these common brain and behavioral indices of adaptive cognitive functioning and moreover, are evident across disorders (i.e., transdiagnostically). Specifically, within each of the disorder classes impairments are consistent in the multiple demand network across a wide range of cognitive tasks. While severity varies between disorders, broad as opposed to domain-specific impairments consistently emerge in neurocognitive performance. Accumulating findings have revealed that phenotypically diverse psychiatric disorders share a common factor or vulnerability to dysfunction that is in turn related to broad neurocognitive deficits. Furthermore, we have observed that regions of the multiple demand network, which overlap with the salience network (dorsal anterior cingulate and bilateral anterior insula) are characterized by reduced gray matter transdiagnostically and predict weaker neurocognitive performance. In summary, transdiagnostic (as opposed to disorder-specific) patterns of symptomatic distress and neurocognitive performance deficits, concurrent with parallel anomalies of brain structure and function may largely contribute to the real-world socio-occupational impairment common across disorders.

Can brain games help smokers quit?: Results of a randomized clinical trial

BACKGROUND AND AIMS

Deficits in cognitive function are observed during nicotine withdrawal and present a challenge to successful smoking cessation. This clinical trial evaluated a cognitive exercise training (CT) program to improve smoking cessation rates.

METHODS

Adult treatment-seeking smokers (n=213) were randomized to receive nicotine patch therapy and 12 weeks of either computerized CT or computerized relaxation (control) training. Smoking status was biochemically verified at the end of treatment and 6-month follow-up.

RESULTS

Quit rates did not differ by treatment arm at either time-point, nor were there effects on withdrawal symptoms or smoking urges. Reaction time for emotion recognition and verbal interference tasks showed improvement in the CT group. When including only successful quitters, improvements in recognition memory, verbal interference accuracy, and attention switching error rate were also observed in the CT group, while commission errors on the continuous performance task decreased in the control group.

CONCLUSIONS

Despite modest changes in cognitive performance, these results do not support the efficacy of computerized cognitive training as an adjunctive therapy for smoking cessation.

Smoke and mirrors: The overnight abstinence paradigm as an index of disrupted cognitive function

RATIONALE

Smoking abstinence is known to cause decrements in cognition, but the effects are small and variable. One way to reduce variance may be to aggregate measures or visits. Although trait-like individual differences in smoking abstinence effects on cognition are theorized to predict relapse, the test-retest reliability (TRR) assumed in trait models has not been evaluated.

OBJECTIVES

The objectives of this study were to assess the value of aggregating measures to determine effect sizes (ESs) of smoking versus abstinence on measures of cognition and to assess the short-term TRR of abstinence effects on cognition.

METHODS

Thirty adult smokers completed the typical overnight abstinence paradigm twice; each visit pair consisted of one smoking visit and one abstinent visit. Measures of attention, working memory, and inhibitory control were obtained in each visit.

RESULTS

There were small to medium ESs for smoking abstinence on individual cognitive measures during the first abstinence experience ("visit pair"). Aggregating the measures within the visit pair and across visit pairs additively increased the ES of smoking versus abstinence. Although TRRs were acceptable between smoking visits and between abstinent visits, TRRs for abstinence effects (smoking vs. abstinent visit differences) on cognition were consistently weak.

DISCUSSION

The ability of the typical overnight abstinence paradigm to reflect disrupted cognition at the group level can be substantially improved by aggregating across cognitive outcomes and/or multiple study visits. However, the patterns of poor TRR of smoking-abstinence differences in cognition caution against their use as trait-like markers in studies of relapse or treatment response.