Smoking-associated changes in the serotonergic systems of discrete regions of human brain

Suicidal ideation, plan, and attempt among men who have sex with men in Nepal: Findings from a cross-sectional study

Men who have sex with men (MSM) are at increased risk for suicide, with a much higher prevalence of suicidality than the general population. While there is a growing interest in the identification of risk factors for suicidal behaviors globally, the understanding of the prevalence and risk factors for suicidal behaviors among MSM in the context of low- and middle-income countries is almost non-existent. Therefore, this study aimed to investigate suicidal ideation, plan, and attempts, and related factors among MSM in Nepal. A cross-sectional respondent driven survey was conducted on 250 MSM between October and December 2022. Bivariate and multivariable logistic regression was used to evaluate independent correlates of suicidal behaviors of MSM. Overall, the lifetime prevalence of suicidal ideation, plans, and attempts among MSM in this study were 42.4%, 31.2%, and 21.6%, respectively. MSM with depressive symptoms (aOR = 5.7, 95% CI = 2.4-14.1), advanced education (higher secondary and above; aOR = 2.9, 95% CI = 1.4-6.1), and smoking habit (aOR = 2.5, 95% CI = 1.2-5.3) were at increased risk for suicidal ideation. Similarly, those with depressive symptoms (aOR = 2.2, 95% CI = 1.1-4.8) and advanced education (aOR = 2.7, 95% CI = 1.2-5.7) were more likely to plan suicide, whereas young MSM were significantly more prone to attempting suicide (aOR = 2.7, 95% CI = 1.3-5.8). Interestingly, MSM with moderate to severe food insecurity were 2-3 times more likely to think about, plan, or attempt suicide (ideation: aOR = 3.5, 95% CI = 1.6-7.7; plan: aOR = 3.7, 95% CI = 1.6-8.3; attempt: aOR = 2.2, 95% CI = 1.1-4.6). The results suggest the importance of early assessment of suicidal behaviors among MSM and the need for tailored interventions to simultaneously address mental health problems and food insecurity to reduce suicide-related problems among Nepalese MSM.

Non-Suicidal Self-Injury in Russian Patients with Suicidal Ideation

BACKGROUND

Nonsuicidal self-injury (NSSI) is recognized as a public health concern for its association with unfavorable outcomes, including suicidal behavior. The aim of this study is to identify factors associated with NSSI among patients with nonpsychotic mental disorders (NPMD) and suicidal ideation in Russia.

METHODS

A retrospective cohort study was conducted in the Moscow Research and Clinical Center for Neuropsychiatry between November 2017 and May 2019. The sample was composed of consecutive patients with lifetime suicidal ideation (from the Self-Injurious Thoughts and Behavior Interview) seen in the center's psychiatric ward for NPMD. The patients were divided into two groups: those with and without lifetime NSSI. Sociodemographic variables, psychiatric diagnosis, family history of mental disorders, history of physical or sexual abuse, sexual behavior, ad-hoc psychiatric treatments, suicidal ideation, plans, and gestures or attempts were investigated.

RESULTS

Six thousand, two hundred and four consecutive patients were screened for suicidal ideation. Out of a total of 361 patients (87.3% females) with suicidal ideation, 217 (60.1%) reported NSSI. Variables independently associated with NSSI included age <25 years (OR 6.0, CI 2.5-14.7), dissatisfaction with the perceived parenting style (OR 3.3, CI 1.5-7.4), bullying (OR 2.6, CI 1.0-6.5), severe body modifications (OR 11.9, CI 1.1-134.3), experience with illicit drugs (OR 4.4, CI 1.9-10.3), and eating disorders (OR 4.9, CI 2.0-11.8).

LIMITATIONS

Retrospective design, referral population, single center study, and exclusion of psychotic patients.

CONCLUSIONS

NSSI is associated with age <25 years old, dissatisfaction with perceived parenting style, bullying, severe body modifications, lifetime experience of illicit drug-use, and lifetime eating disorders.HIGHLIGHTSNonsuicidal self-injury is a significant public health concern for its association with suicidal behavior.60.1% of Russian patients with non-psychotic mental disorders (NPMD) and suicidal ideation reported lifetime NSSI.NSSI in Russian patients with NPMD and suicidal ideation is associated with age less than 25 years, dissatisfaction with perceived parenting style, bullying, severe body modifications, lifetime experience of illicit drug use, and lifetime eating disorders.

Smoking enhances suicide risk-a significant role in the COVID-19 pandemic?

The COVID-19 outbreak has severely affected the whole world. Considerable evidence suggests that tobacco smoking is associated with increased severity of COVID-19 and death in COVID-19 patients. Tobacco smoking cessation is necessary to decrease COVID-19-related hospitalizations and deaths. In this commentary, I suggest that tobacco smoking cessation is also needed to reduce suicidal behavior during and after the COVID-19 pandemic. Significant evidence suggests that the COVID-19 pandemic leads to increased tobacco consumption as smokers use more tobacco to cope with pandemic-related stress, anxiety, depression and loneliness. Multiple studies have demonstrated that tobacco smoking is associated with suicidal ideation, suicide attempts, suicide death and a contributing factor in the pathophysiology of suicide. Smoking may increase the probability of development of post-COVID syndrome because it increases severity of COVID-19. Suicide risk may be increased in individuals with post-COVID syndrome. Smoking prevention and cessation should be a target of suicide prevention interventions during and after the COVID-19 pandemic. The COVID-19 pandemic enhances the need to act to integrate tobacco smoking cessation in the health care as a standard of patient care.

Interaction of smoking and being bullied on suicidal behaviors: a school-based cross-sectional survey in China

BACKGROUND

Suicidal behaviors are seriously social issues among adolescents in the world. Exposed to smoking and being bullied are risk factors of suicidal behaviors. The present study was aimed to examine the interaction of smoking and being bullied on suicidal behaviors among Chinese adolescents.

METHODS

A total of 18,900 students were involved in the questionnaire study, in four cities of China from November 2017 to January 2018. Suicidal behaviors, smoking, and being bullied were measured by self-reported validated instruments. Chi-square tests and logistic regression were used to analyze the associations of suicidal ideation (SI)/suicidal plan (SP)/suicidal attempt (SA), smoking, and being bullied.

RESULTS

The prevalence of smoking, being bullied, SI/SP/SA, were 3.1%, 20.6%, 26.4%, 13.2%, and 5.2% respectively. Interaction analysis indicated that being bullied was associated with a greater increase in the likelihood of suicidal behaviors for adolescents with smoking than for those without smoking.

CONCLUSIONS

These finding suggest that smoking exacerbates the association between being bullied and suicidal behaviors. Future research should explore how and why smoking appears to more bully-victims than for those without smoking and how to mitigate it.

Serotonin neurons in the median raphe nucleus bidirectionally regulate somatic signs of nicotine withdrawal in mice

In chronic smokers, nicotine withdrawal symptoms during tobacco cessation can lead to smoking relapse. In rodent models, chronic exposure to nicotine elicited physical dependence, whereas acute antagonism of nicotinic acetylcholine receptors (nAChRs) immediately precipitated withdrawal symptoms. Although the central serotonergic system plays an important role in nicotine withdrawal, the exact serotonergic raphe nuclei regulating these symptoms remain unknown. We used transgenic mice expressing archaerhodopsinTP009 or channelrhodopsin-2[C128S] exclusively in the central serotonergic neurons to selectively manipulate serotonergic neurons in each raphe nucleus. Nicotine withdrawal symptoms were precipitated by an acute injection of mecamylamine, a nonspecific nAChR antagonist, following chronic nicotine consumption. Somatic signs were used as measures of nicotine withdrawal symptoms. Acute mecamylamine administration significantly increased ptosis occurrence in nicotine-drinking mice compared with that in control-drinking mice. Optogenetic inhibition of the serotonergic neurons in the median raphe nucleus (MRN), but not of those in the dorsal raphe nucleus (DRN), mimicked the symptoms observed during mecamylamine-precipitated nicotine withdrawal even in nicotine-naïve mice following the administration of acute mecamylamine injection. Optogenetic activation of the serotonergic neurons in the MRN nearly abolished the occurrence of ptosis in nicotine-drinking mice. The serotonergic neurons in the MRN, but not those in the DRN, are necessary for the occurrence of somatic signs, a nicotine withdrawal symptom, and the activation of these neurons may act as a potential therapeutic strategy for preventing the somatic manifestations of nicotine withdrawal.

How Does COVID-19 Affect the Neurobiology of Suicide?

PURPOSE OF REVIEW

The aim of this review was to analyze COVID-19 effect on the biological features of suicidal vulnerability and its interaction with suicide-related biological pathways. We carried out a narrative review of international publications on the interactions of COVID-19 with the biological bases of suicide.

RECENT FINDINGS

We hypothesize that SARS-CoV-2 interacts with multiple biological processes that underlie suicidal behavior, such as the renin-angiotensin system, nicotinic receptors, and central and systemic inflammation. Social distancing measures may also worsen subjective or objective social disconnection, thus increasing the risk of suicide. Interestingly, the drugs used to prevent suicide could be promising options to counteract brain damage caused by this coronavirus. SARS-CoV-2 interacts with multiple biological pathways involved in suicide and opens a new window for understanding the suicidal process. The development of suicide prevention treatments in the context of a pandemic may benefit from knowledge on these interactions.

Association of Tobacco Use and Exposure to Secondhand Smoke With Suicide Attempts Among Adolescents: Findings From 33 Countries

INTRODUCTION

There is evidence to suggest that tobacco use is associated with suicide attempts. However, it is unclear whether such an association can be extended to include secondhand smoke exposure. Using nationally representative data of school-attending adolescents from 33 countries, we examined the association of tobacco use and exposure to secondhand smoke with suicide attempts.

METHODS

We used data from the Global School-based Student Health Survey, a cross-sectional survey conducted among adolescents 12-15 years of age. We used logistic regression to estimate the country-specific associations. We then conducted random effect meta-analyses to obtain overall and country-income level pooled estimates. Lastly, we used logistic regression analyses to investigate a dose-response association of cigarette smoking and exposure to secondhand smoke with suicide attempts.

RESULTS

A positive association between tobacco use and suicide attempts among adolescents was present regardless of country-income level (low income: odds ratio 4.98, 95% CI: 3.11-7.96; lower middle income: 3.47, 2.91-4.15; upper middle income: 3.09, 2.75-3.47; and high income: 3.18, 2.63-3.84) and gender (boys: 3.28, 2.86-3.76; girls: 3.86, 3.30-4.51). Exposure to secondhand smoke was associated with suicide attempts, albeit weakly, among girls only (1.26, 1.14-1.39; boys: 1.00, 0.87-1.15). There was some evidence that a dose-response association of cigarette smoking and exposure to secondhand smoke with suicide attempts may only exist among girls.

CONCLUSIONS

Adolescents who use tobacco, and adolescent girls exposed to secondhand smoke were found to be more likely to attempt suicide; however, future longitudinal studies are warranted to assess causality.

IMPLICATIONS

Our findings indicate that routine screening of adolescents for tobacco use should be implemented globally, especially when assessing suicidal behaviors and risk. Future longitudinal and intervention studies are warranted to assess causality and whether prevention efforts such as tobacco control interventions and programmes targeting tobacco use and exposure to secondhand smoke among adolescents could ultimately lead to a reduction in the occurrence of suicide attempts.

An analysis of the relationship between chronic obstructive pulmonary disease, smoking and depression in an integrated healthcare system

OBJECTIVE

Chronic Obstructive Pulmonary Disease (COPD) and smoking are highly associated with depression and hypoxia. There is limited knowledge about whether hypoxic conditions interact to cause depression.

METHOD

A population-based cohort study was conducted using the Veterans Affairs (VA) Corporate Data Warehouse. Patients must have accessed any healthcare at a VA facility between 2004 and 2014 and had a negative depression screen (Patient Health Questionnaire-2 (PHQ-2) score ≤ 2). Patients with COPD or a positive depression screen (PHQ-2 score: 3+) during or prior to the year with a negative depression screen were excluded. Logistic regression with annual observations was used to evaluate depression incidence based on COPD and smoking status. Models were adjusted for demographics and other comorbid conditions. A probability scale was used to examine interactions between COPD and smoking.

RESULTS

A total of 3,284,496 patients were included. Patients with COPD and current smokers were at increased risk for developing depression. There were minimal interaction effects between COPD and smoking. The odds of developing depression in a year varied from 1.4% among never smokers without COPD to 2.9.% among current smokers with COPD.

CONCLUSION

Smoking and COPD are independent risk factors for depression and interact to cause depression. Further research is needed to confirm whether hypoxia contributes to this association.

Association between cigarette use and adolescents' behavior

OBJECTIVE

To determine the prevalence of cigarette use among adolescents and to identify associated health risk behaviors.

METHODS

This is a cross-sectional study with a representative sample, composed of 1059 adolescents between 13 and 19 years old, enrolled in primary and secondary public schools of Olinda, Pernambuco, in 2014. Information was obtained through self-administered questionnaires (validated version of YRBS 2007). Cigarette experimentation was defined as smoking at least once in life. Adolescents who smoked at least one day within 30 days prior to the survey were considered current smokers. Most students were female and 16 years old or older.

RESULTS

Almost 30% used it in life and about 10% smoked within the 30 days before the survey. Suicidal ideation (PR = 1.51, 95%CI 1.25-1.82), alcohol use (PR = 1.41, 95%CI 1.03-1.92), marijuana (PR = 1.64, 95%CI 1.37-1.96), excessive alcohol consumption (PR = 1.57, 95%CI 1.15-2.16) and sexual experience (PR = 1.78, 95%CI 1.43-2.21) have increased the risk of using cigarettes. Feelings of sadness (PR = 1.70, 95%CI 1.22-2.36), alcohol use (PR=2.40, 95%CI 1.12-5.12), excessive alcohol consumption (PR = 2.5, 95% CI 1.24-5.38), marijuana (PR = 2.31, 95%CI.57-3.39) and cocaine (PR = 1.99, 95%CI.32-3.01) increased the risk of cigarette use within the 30 days before the survey.

CONCLUSIONS

Cigarette use among adolescents from Olinda was high, being considered higher than the national prevalence. Possible factors associated with cigarette use were drug use (alcohol, marijuana, and cocaine) and behaviors related to sexual experience, feelings of sadness and suicidal ideation.

Living High and Feeling Low: Altitude, Suicide, and Depression

After participating in this activity, learners should be better able to:• Assess epidemiologic evidence that increased altitude of residence is linked to increased risk of depression and suicide• Evaluate strategies to address hypoxia-related depression and suicidal ideation ABSTRACT: Suicide and major depressive disorder (MDD) are complex conditions that almost certainly arise from the influences of many interrelated factors. There are significant regional variations in the rates of MDD and suicide in the United States, suggesting that sociodemographic and environmental conditions contribute. Here, we review epidemiological evidence that increases in the altitude of residence are linked to the increased risk of depression and suicide. We consider the possibility that chronic hypobaric hypoxia (low blood oxygen related to low atmospheric pressure) contributes to suicide and depression, which is suggested by animal models, short-term studies in humans, and the effects of hypoxic medical conditions on suicide and depression. We argue that hypobaric hypoxia could promote suicide and depression by altering serotonin metabolism and brain bioenergetics; both of these pathways are implicated in depression, and both are affected by hypoxia. Finally, we briefly examine treatment strategies to address hypoxia-related depression and suicidal ideation that are suggested by these findings, including creatine monohydrate and the serotonin precursors tryptophan and 5-hydroxytryptophan.

Functional Connectivity of the Raphe Nuclei: Link to Tobacco Withdrawal in Smokers

BACKGROUND

Although nicotine alters serotonergic neurochemistry, clinical trials of serotonergic medications for smoking cessation have provided mixed results. Understanding the role of serotonergic dysfunction in tobacco use disorder may advance development of novel pharmacotherapies.

METHODS

Functional magnetic resonance imaging was used to measure resting-state functional connectivity of the raphe nuclei as an indicator of serotonergic function. Connectivity of the dorsal and median raphe nuclei was compared between 18 young smokers (briefly abstinent, ~40 minutes post-smoking) and 19 young nonsmokers (16-21 years old); connectivity was also examined in a separate sample of overnight-abstinent smokers (18-25 years old), before and after smoking the first cigarette of the day. Relationships between connectivity of the raphe nuclei with psychological withdrawal and craving were tested in smokers.

RESULTS

Connectivity of the median raphe nucleus with the right hippocampal complex was weaker in smokers than in nonsmokers and was negatively correlated with psychological withdrawal in smokers. In overnight-abstinent smokers, smoking increased connectivity of the median raphe nucleus with the right hippocampal complex, and the increase was positively correlated with the decrease in psychological withdrawal.

CONCLUSIONS

Relief of withdrawal due to smoking is potentially linked to the serotonergic pathway that includes the median raphe nucleus and hippocampal complex. These results suggest that serotonergic medications may be especially beneficial for smokers who endorse strong psychological withdrawal during abstinence from smoking.

Temporal sequencing of nicotine dependence and major depressive disorder: A U.S. national study

Major Depressive Disorder (MDD) and Nicotine dependence (ND) often co-occur. However, little attention has been given to the temporal order between the two disorders. We compared the sociodemographic and clinical characteristics of individuals whose onset of ND preceded (ND-prior) or followed the onset of MDD (MDD-prior). Binary logistic regression models were computed to compare ND-prior (n=546) and MDD-prior (n=801) individuals from the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC, n=43,093). We found that MDD-prior were more likely to have a history of suicide attempts and a family history of both depression and antisocial behavior, to have had psychiatric hospitalization, and to have an earlier age of onset of the first depressive episode; but a later age of onset for both daily smoking and ND. On average, MDD-prior individuals showed a significantly longer transition time from daily smoking to ND (15.6±0.6 vs. 6.9±0.4 years, P<0.001). In contrast, ND-prior subjects had a significantly greater proportion of withdrawal symptoms, and of lifetime alcohol use or alcohol use disorder. We conclude that the phenomenology and course of ND and MDD vary significantly, depending on which disorder had earlier onset.

Smoking and Suicide: A Meta-Analysis

BACKGROUND

Many studies have reported a positive association between smoking and suicide, but the results are inconsistent. This meta-analysis was carried out to estimate the association between smoking and suicidal ideation, suicide plan, suicide attempt, and suicide death.

METHODS

Major electronic databases including PubMed, Web of Science, Scopus, and ScienceDirect were searched until May 2015. The reference lists of included studies were screened too. Epidemiological studies addressing the association between smoking and suicidal behaviors were enrolled. The heterogeneity across studies was explored by Q-test and I2 statistic. The possibility of publication bias was assessed using Begg's and Egger's tests and Trim & Fill analysis. The results were reported based on risk ratio (RR) and odds ratio (OR) with 95% confidence intervals (CI) using a random-effects model.

RESULTS

We identified a total of 8062 references and included 63 studies with 8,063,634 participants. Compared to nonsmokers, the current smokers were at higher risk of suicidal ideation (OR = 2.05; 95% CI: 1.53, 2.58; 8 studies; I2 = 80.8%; P<0.001), suicide plan (OR = 2.36; 95% CI: 1.69, 3.02; 6 studies; I2 = 85.2%; P<0.001), suicide attempt (OR = 2.84; 95% CI: 1.49, 4.19; 5 studies; I2 = 89.6%; (P<0.001), and suicide death (RR = 1.83; 95% CI: 1.64, 2.02; 14 studies; I2 = 49.7%; P = 0.018).

CONCLUSIONS

There is sufficient evidence that smoking is associated with an increased risk of suicidal behaviors. Therefore, smoking is a contributing factor for suicide. Although this association does not imply causation, however, smoking prevention and cessation should be the target of suicide prevention programs.

Cigarette Smoking and Tryptophan Hydroxylase 2 mRNA in the Dorsal Raphe Nucleus in Suicides

Cigarette smoking is associated with suicide and mood disorders and stimulates serotonin release. Tryptophan hydroxylase (TPH2) synthesizes serotonin and is over-expressed in suicides. We determined whether smoking is associated with TPH2 mRNA in suicides and controls. TPH2 mRNA was measured postmortem in the dorsal raphe nucleus (DRN) of controls (N = 26, 17 nonsmokers and nine smokers) and suicides (N = 23, 5 nonsmokers and 18 smokers). Psychiatric history was obtained by psychological autopsy. TPH2 mRNA was greater in suicide nonsmokers than suicide smokers, control smokers and control nonsmokers (p = 0.006). There was more TPH2 mRNA throughout the DRN. Smoking interferes with the TPH2 mRNA increase observed in suicide nonsmokers. The absence of altered TPH2 expression in non-suicide smokers suggests no pharmacological effect of smoking.

Tobacco use is associated with reduced amplitude and intensity dependence of the cortical auditory evoked N1-P2 component

RATIONALE

Tobacco use is linked to cerebral atrophy and reduced cognitive performance in later life. However, smoking-related long-term effects on brain function remain largely uncertain. Previous studies suggest that nicotine affects serotonergic signaling, and the intensity dependence (alias loudness dependence) of the auditory evoked N1-P2 potential has been proposed as a marker of serotonergic neurotransmission.

OBJECTIVE

In the present study, we assesed the effects of chronic smoking on amplitude and intensity dependence of the auditory evoked N1-P2 potential.

METHODS

Subjects underwent a 15-min intensity dependence of auditory evoked potentials (IAEP) paradigm. From N = 1739 eligible subjects (40-79 years), we systematically matched current smokers, ex-smokers, and never-smokers by sex, age, alcohol and caffeine consumption, and socioeconomic status. Between-group differences and potential dose-dependencies were evaluated.

RESULTS

Analyses revealed higher N1-P2 amplitudes and intensity dependencies in never-smokers relative to ex- and current smokers, with ex-smokers exhibiting intermediate intensity dependencies. Moreover, we observed pack years and number of cigarettes consumed per day to be inversely correlated with amplitudes in current smokers.

CONCLUSIONS

According to the IAEP serotonin hypothesis, our results suggest serotonin activity to be highest in current smokers, intermediate in ex-smokers, and lowest in never-smokers. To our knowledge, the present study is the first providing evidence for a dose-dependent reduction in N1-P2 amplitudes. Further, we extend prior research by showing reduced amplitudes and intensity dependencies in ex-smokers even 25 years, on average, after cessation. While we can rule out several smoking-related confounders to bias observed associations, causal inferences remain to be established by future longitudinal studies.

Smoking and the Association Between Depressive Symptoms and Absolute Neutrophil Count in the Investigations Préventives et Cliniques Cohort Study

OBJECTIVES

Depressive symptoms have been associated with chronic low-grade inflammation, including elevated neutrophil count. Smokers often have both high neutrophil count and depressive symptoms. Thus, smoking could explain the cross-sectional association between depressive symptoms and neutrophil count.

METHODS

Total white blood cell count and subtypes, including absolute neutrophil, lymphocyte, monocyte, basophil, and eosinophil counts, were measured in 44,806 participants (28,534 men; mean [standard deviation] age = 38.9 [11.4] years), without a history of chronic disease or current medication. Depressive symptoms were assessed with the Questionnaire of Depression, Second Version, Abridged. Smoking status was self-reported and categorized in five classes. Sex, age, alcohol intake, self-rated health, body mass index, glycemia, physical activity, household composition, occupational status, and education were included as covariates. Associations were examined with general linear models and causal mediation analyses.

RESULTS

After adjustment for all covariates except smoking, depressive symptoms were positively associated with neutrophil count only (β = 5.83, standard error [SE] = 2.41, p = .014). After further adjustment for a semiquantitative measure of smoking, this association was no longer significant (β = 2.40, SE = 2.36, p = .30). Causal mediation analyses revealed that smoking mediated the association (p < .001), accounting for 57% of its total variance. In contrast, depressive symptoms were negatively associated with lymphocyte count in fully adjusted model only (β = -3.21, SE = 1.11, p = .004).

CONCLUSIONS

Smoking may confound or mediate the association between depressive symptoms and neutrophil count. These results advocate for including an accurate measure of smoking in future studies addressing this association. When considering the link between depression and inflammation, one should not overlook the noxious effects of smoking.

Smoking, Suicidality and Psychosis: A Systematic Meta-Analysis

The aim of this study is to systematically review the literature that explored the association between smoking and suicidal risk among those with serious mental illness and to estimate the risk of suicidal behaviors attributable to smoking among this patient group. Multiple databases (CINAHL, PsycINFO, EMBASE, Informit Health Collection and the Cochrane Library databases) were searched from 1 January 1975 through 15 January 2014, along with references from relevant articles for observational studies that ascertained the association between smoking and suicidal behaviors among patients with psychotic disorders conducted in adult patients. Thirteen studies involving 6813 patients with severe mental illness were included. We found that smoking was significantly associated with suicidality in psychosis with an Odds Ratio of 2.12 (95% CI 1.67–2.7). Smoking is associated with suicidal risk amongst individuals with a severe mental illness; however, it is still unclear whether this represents a true risk factor or a confounder or a mediator via mechanisms, hitherto unknown, needs to be studied further.

Bacoside A: Role in Cigarette Smoking Induced Changes in Brain

Cigarette smoking (CS) is a major health hazard that exerts diverse physiologic and biochemical effects mediated by the components present and generated during smoking. Recent experimental studies have shown predisposition to several biological consequences from both active and passive cigarette smoke exposure. In particular, passive smoking is linked to a number of adverse health effects which are equally harmful as active smoking. A pragmatic approach should be considered for designing a pharmacological intervention to combat the adverse effects of passive smoking. This review describes the results from a controlled experimental condition, testing the effect of bacoside A (BA) on the causal role of passive/secondhand smoke exposure that caused pathological and neurological changes in rat brain. Chronic exposure to cigarette smoke induced significant changes in rat brain histologically and at the neurotransmitter level, lipid peroxidation states, mitochondrial functions, membrane alterations, and apoptotic damage in rat brain. Bacoside A is a neuroactive agent isolated from Bacopa monnieri. As a neuroactive agent, BA was effective in combating these changes. Future research should examine the effects of BA at molecular level and assess its functional effects on neurobiological and behavioral processes associated with passive smoke.

Suicidal Ideation, Suicidal Plan and Suicidal Attempts Among Those with Major Depressive Disorder

Introduction: The aims of the study were to identify the prevalence and sociodemographic and clinical correlates of suicidal behaviours using data from a cross-sectional survey among those with major depressive disorder (MDD) in Singapore. Materials and Methods: The Singapore Mental Health Study (SMHS) was a cross-sectional epidemiological study that surveyed Singapore residents (Singapore citizens and permanent residents) aged 18 years and above. The assessment of mental disorders was established using version 3.0 of the Composite International Diagnostic Interview (CIDI 3.0). For the purposes of this study, suicidal behaviour was assessed by questions which were asked to respondents who answered positively to the screening questions in the CIDI 3.0 “Depression” module. Results: The prevalence of suicidal ideation, plan and attempt among those with lifetime MDD was 43.6%, 13.7% and 12.3%, respectively. We found that suicidal ideation, plan and attempt were significantly associated with ethnicity, education and income. The rate of those who had sought some professional help was higher among those with suicidal plan (71.7%) and attempt (72.3%) as compared to those with suicidal ideation (48.7%) and those with MDD but no suicidal behaviour (29%). Conclusion: Individuals with MDD and suicidal behaviour do differ from their non-suicidal counterparts as they have a different sociodemographic and clinical profile. There is a need for more research and a better understanding of this population which in turn could lead to the development and implementation of relevant interventions. Key words: Composite International Diagnostic Interview, Depression, Prevalence, Singapore Mental Health Study, Suicidal behaviour

Cigarette smoking and obesity are associated with decreased fat perception in women

OBJECTIVE

Smoking and obesity are independently associated with high consumption of high-fat foods in women. We tested whether the co-occurrence of smoking and obesity associates with reduced oral fat perception.

METHODS

Four groups of women (14 obese smokers, 11 obese never-smokers, 10 normal-weight smokers, 12 normal-weight never-smokers) rated vanilla puddings that varied in fat content for perceived intensity of creaminess and sweetness, using the general Labeled Magnitude Scale (gLMS), and degree of pleasantness, using the hedonic gLMS. To determine the role of retronasal smell, subjects rated puddings with and without noseclips.

RESULTS

For all groups, perception of creaminess grew with increasing fat concentrations; puddings with any amount of fat were perceived as sweeter than fat-free pudding, and sweetness was enhanced when tasted without noseclips. Overall, obese smokers perceived less creaminess, sweetness, and pleasure while tasting the puddings than did the other three groups (all P values < 0.02).

CONCLUSION

The ability to perceive fat and sweetness in and derive pleasure from foods is particularly compromised in obese women who smoke, which could contribute to excess calorie intake in this population already at high risk for cardiovascular and metabolic disease. Retronasal olfaction appears not to contribute to blunted flavor perception observed in obese smokers.

Elevated incidence of suicide in people living at altitude, smokers and patients with chronic obstructive pulmonary disease and asthma: possible role of hypoxia causing decreased serotonin synthesis

Recent research indicates that suicide rates are elevated in those living at higher altitudes in both the United States and South Korea. A possible mechanism that was proposed is metabolic stress associated with hypoxia. This commentary discusses these results, and also the association between elevated suicide rates and other conditions associated with hypoxia (smoking, chronic obstructive pulmonary disease and asthma). Tryptophan hydroxylase may not normally be saturated with oxygen, so mild hypoxia would decrease serotonin synthesis. Low brain serotonin is known to be associated with suicide. Thus, the commentary proposes and discusses the hypothesis that decreased brain serotonin synthesis associated with hypoxia is a mechanism that may contribute to suicide in conditions causing hypoxia. Finally the commentary proposes various studies that could test aspects of this hypothesis.

The moderating influence of nicotine and smoking on resting-state mood and EEG changes in remitted depressed patients during tryptophan depletion

Comorbidity between depression and tobacco use may reflect self-medication of serotonergically mediated mood dysregulation, which has been associated with aberrant cortical activation and hemispheric asymmetry in patients with major depressive disorders (MDD). This randomized, double-blind study in 28 remitted MDD patients examined the moderating effects of acute nicotine and smoker vs. nonsmoker status on mood and EEG changes accompanying transient reductions in serotonin induced by acute tryptophan depletion (ATD). In smokers, who exhibited greater posterior high alpha power and increased left frontal low alpha power (signs of deactivation) compared to nonsmokers, ATD increased self-ratings of depressed mood and elevated left frontal and right parietal high alpha power (i.e. further cortical deactivation). Smokers were not affected by nicotine administration. In nonsmokers, ATD did not influence depression ratings, but it reduced vigor ratings and increased frontal and posterior theta power; both of which were blocked by acute nicotine. These findings indicate a role for nicotinic receptors in disordered mood.

Temporal sequencing of nicotine dependence and bipolar disorder in the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC)

Bipolar disorder (BD) and nicotine dependence (ND) often co-occur. However, the mechanisms underlying this association remain unclear. We aimed to examine, for the first time in a national and representative sample, the magnitude and direction of the temporal relationship between BD and ND; and to compare, among individuals with lifetime ND and BD, the sociodemographic and clinical characteristics of individuals whose onset of ND preceded the onset of BD (ND-prior) with those whose onset of ND followed the onset of BD (BD-prior). The sample included individuals with lifetime BD type I or ND (n = 7958) from the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC, n = 43093). Survival analyses and logistic regression models were computed to study the temporal association between ND and BD, and to compare ND-prior (n = 135) and BD-prior (n = 386) individuals. We found that ND predicted the onset of BD and BD also predicted the onset of ND. Furthermore, the risk of developing one disorder following the other one was greatest early in the course of illness. Most individuals with lifetime ND and BD were BD-prior (72.6%). BD-prior individuals had an earlier onset of BD and a higher number of manic episodes. By contrast, ND-prior individuals had an earlier onset of both daily smoking and ND, and an increased prevalence of alcohol use disorder. In conclusion, ND and BD predict the development of each other. The phenomenology and course of ND and BD varied significantly depending on which disorder had earlier onset.

Animal models of nicotine exposure: relevance to second-hand smoking, electronic cigarette use, and compulsive smoking

Much evidence indicates that individuals use tobacco primarily to experience the psychopharmacological properties of nicotine and that a large proportion of smokers eventually become dependent on nicotine. In humans, nicotine acutely produces positive reinforcing effects, including mild euphoria, whereas a nicotine abstinence syndrome with both somatic and affective components is observed after chronic nicotine exposure. Animal models of nicotine self-administration and chronic exposure to nicotine have been critical in unveiling the neurobiological substrates that mediate the acute reinforcing effects of nicotine and emergence of a withdrawal syndrome during abstinence. However, important aspects of the transition from nicotine abuse to nicotine dependence, such as the emergence of increased motivation and compulsive nicotine intake following repeated exposure to the drug, have only recently begun to be modeled in animals. Thus, the neurobiological mechanisms that are involved in these important aspects of nicotine addiction remain largely unknown. In this review, we describe the different animal models available to date and discuss recent advances in animal models of nicotine exposure and nicotine dependence. This review demonstrates that novel animal models of nicotine vapor exposure and escalation of nicotine intake provide a unique opportunity to investigate the neurobiological effects of second-hand nicotine exposure, electronic cigarette use, and the mechanisms that underlie the transition from nicotine use to compulsive nicotine intake.

The Relationship between Smoking Status and Suicidal Behavior in Korean Adults: The 4th Korea National Health and Nutrition Examination Survey (2007-2009)

BACKGROUND

This study was performed to evaluate the relationship between smoking status and suicidal ideations or suicide attempts in Korean adults.

METHODS

The study used data from the 4th Korea National Health and Nutrition Examination Survey, and involved 17,065 participants. We used multiple logistic regression analysis to evaluate the relationship between smoking status and suicidal behavior. The results were adjusted for covariates including depression and physical disease.

RESULTS

After adjusting for covariates, current smokers (odds ratio [OR], 1.66; 95% confidence interval [CI], 1.34 to 2.05) and former smokers (OR, 1.39; 95% CI, 1.13 to 1.72) proved more likely to have suicidal ideations than non-smokers. Among women, current smokers (OR, 2.00; 95% CI, 1.47 to 2.72) and former smokers (OR, 1.48; 95% CI, 1.11 to 1.99) were more likely to have suicidal ideations than non-smokers. However, among the men there was no significant relationship between smoking status and suicidal ideations. Among all the participants who had had suicidal ideations, there was a significant relationship between current smoking and suicide attempts (OR, 1.80; 95% CI, 1.05 to 3.07). There was also a relationship between current smoking and suicide attempts among women (OR, 2.40; 95% CI, 1.31 to 4.37), but no significant relationship among men.

CONCLUSION

There is a relationship between smoking status and suicidal ideations and suicide attempts in the general population of Korea. This relationship is particularly clear in women, and is independent of comorbid chronic disease and depression. Current smokers and former smokers are more likely to have suicidal ideations than non-smokers; current smokers are also more likely to have attempted suicide.

Stress response dysregulation and stress-induced analgesia in nicotine dependent men and women

Alterations in the stress response and endogenous pain regulation mechanisms may contribute directly and indirectly to maintenance of nicotine dependence and relapse. We examined the extent to which nicotine dependence alters endogenous pain regulatory systems, including the hypothalamic-pituitary-adrenocortical axis, cardiovascular activity, and stress-induced analgesia. Smokers and nonsmokers attended a laboratory session that included assessment of hormonal and cardiovascular responses to stress. Smokers smoked at their regular rate prior to the session. The hand cold pressor and heat thermal pain tests were completed twice, once after acute stress (public speaking and math tasks) and the other after rest. While smokers and nonsmokers exhibited significant hormonal and cardiovascular responses to stress, smokers exhibited blunted stress responses relative to nonsmokers. They also exhibited diminished stress-induced analgesia. Results demonstrate altered stress response and diminished stress-induced analgesia among chronic smokers, and suggest that these dysregulated physiological responding may contribute to altered endogenous pain regulation.

Cigarette smoking and risk of completed suicide: a meta-analysis of prospective cohort studies

BACKGROUND

Epidemiologic studies have reported conflicting results relating smoking to suicide risk. We conducted a meta-analysis of prospective cohort studies to evaluate the association of cigarette smoking with completed suicide.

METHODS

Eligible prospective cohort studies were identified from PubMed and EMbase databases (from 1966 to May 2011) and the reference lists of retrieved articles. Two authors independently extracted data and assessed study quality using the Newcastle-Ottawa Scale. Study-specific risk estimates were pooled using random-effects model and generalized least squares trend estimation was used to assess dose-response relationship.

RESULTS

Fifteen prospective cohort studies involving 2395 cases among 1,369,807 participants were included in the meta-analysis. Our data suggested that cigarette smoking significantly increased the risk of completed suicide. Compared with never smokers, the pooled RR was 1.28 (95% CI: 1.001-1.641) for former smokers, and 1.81 (95% CI: 1.50-2.19) for current smokers, respectively. Subgroup analyses showed that the increased suicide risk among current smokers appeared to be consistent, although there was heterogeneity among studies of current smoking (p < 0.001). Significant dose-response relationship was found between smoking and suicide, and the risk of suicide was increased by 24% for each increment of 10 cigarettes smoked per day (RR, 1.24; 95% CI: 1.20-1.28).

CONCLUSIONS

Our meta-analysis robustly demonstrates that cigarette smoking is associated with an increased risk of completed suicide, consistent with a dose-response relationship. This conclusion has an important public health message for countries with high smoking prevalence and high suicide rate such as China.

Persistent heavy smoking as risk factor for major depression (MD) incidence--evidence from a longitudinal Canadian cohort of the National Population Health Survey

BACKGROUND

Reports of bidirectional associations between smoking and major depression (MD) have been interpreted as providing evidence for confounding by shared-vulnerability factors (SV) that predispose individuals to both conditions. If this is true, then smoking cessation may not reduce the risk of MD. From clinical practice and public health perspectives, the long-term outcomes associated with smoking persistence and cessation are potentially important and deserve exploration. To this end, the 12-year risk of MD in persistent heavy smokers and abstainers who were former-heavy smokers with and without adjustment for potential confounders were compared.

METHODS

Follow-up data from the National Population Health Survey (NPHS) was used. Multinomial logistic (ML) models were fit to identify potential confounders. Using proportional hazard (PH) models, unadjusted and adjusted hazard ratios (HRs) for MD outcome were estimated for different smoking patterns.

RESULTS

The unadjusted HR relating the risk of MD among current-heavy versus former-heavy smokers was 4.3 (95% CI: 2.6-6.9, p < 0.001). Current-heavy smoking predicted onset of MD (HR = 3.1, 95% CI: 1.9-5.2, p < 0.001) even after adjustment for age, sex and stress - the main confounders. However, this was not the case for the never, former-light, and current-light categories. Evidence of decreased risk of MD among former-heavy relative to current-heavy smokers as function of smoking cessation maintenance time was also found.

CONCLUSIONS

Contrary to common beliefs about the benefits of smoking for mental health, our results suggest that current-heavy rather than ever-heavy smoking is a major determinant of MD risk and point towards the benefits of smoking cessation maintenance.

Shifting topographic activation and 5-HT1A receptor-mediated inhibition of dorsal raphe serotonin neurons produced by nicotine exposure and withdrawal

Nicotine activates serotonin [5-hydroxytryptamine (5-HT)] neurons innervating the forebrain, and this is thought to reduce anxiety. Nicotine withdrawal has also been associated with an activation of 5-HT neurotransmission, although withdrawal increases anxiety. In each case, 5-HT1A receptors have been implicated in the response. To determine whether there are different subgroups of 5-HT cells activated during nicotine administration and withdrawal, we mapped the appearance of Fos, a marker of neuronal activation, in 5-HT cells of the dorsal raphe nucleus (DR) and median raphe nucleus (MR). To understand the role of 5-HT1A receptor feedback inhibitory pathways in 5-HT cell activity during these conditions, we administered a selective 5-HT1A receptor antagonist and measured novel disinhibited Fos expression within 5-HT cells. Using these approaches, we found evidence that acute nicotine exposure activates 5-HT neurons rostrally and in the lateral wings of the DR, whereas there is 5-HT1A receptor-dependent inhibition of cells located ventrally at both the rostral level and mid-level. Previous chronic nicotine exposure did not modify the pattern of activation produced by acute nicotine exposure, but increased 5-HT1A receptor-dependent inhibition of 5-HT cells in the caudal DR. This pattern was nearly reversed during nicotine withdrawal, when there was evidence for caudal activation and mid-level and rostral 5-HT1A receptor-dependent inhibition. These results suggest that the distinct behavioral states produced by nicotine exposure and withdrawal correlate with reciprocal rostral-caudal patterns of activation and 5-HT1A receptor-mediated inhibition of DR 5-HT neurons. The complementary patterns of activation and inhibition suggest that 5-HT1A receptors may help to shape distinct topographic patterns of activation within the DR.

The relation between nicotine dependence and suicide attempts in the general population

OBJECTIVE

There has been much debate as to whether nicotine is a risk factor for suicidal behaviour. This study sought to examine the relation between nicotine dependence and suicide attempts in a population-based sample of adults.

METHOD

Our study used the National Epidemiologic Survey on Alcohol and Related Conditions Wave 2 (NESARC; 2004-2005), a large (n = 34,653) nationally representative survey of community-dwelling American adults. Multiple logistic regression analyses examined the relation between suicide attempts and Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, nicotine dependence, compared with nonusers of nicotine. Associations between suicide attempts and other measures of nicotine use (nicotine cessation, age of first use, frequency, and amount of use) were also examined.

RESULTS

Lifetime (AOR 1.78; 95% CI 1.48 to 2.15) and past-year nicotine dependence (AOR 1.77; 95% CI 1.02 to 3.06) were independently associated with lifetime and past-year suicide attempts, respectively, even after adjusting for sociodemographic factors, other mental disorders, and physical disease. Nicotine dependence cessation was associated with a decreased likelihood of suicide attempt compared with people currently dependent on nicotine (AOR 0.15; 95% CI 0.05 to 0.43). Greater amount of daily cigarette use was associated with suicide attempts in the model that adjusted for sociodemographic factors and other mental disorders (AOR 1.53; 95% CI 1.05 to 2.24).

CONCLUSIONS

Nicotine dependence is associated with suicide attempts, independently of comorbid mental disorders and physical disease. The association attenuates when a person ceases using nicotine, suggesting a state, rather than trait, effect. These findings provide evidence for additional concern regarding the deleterious health effects of tobacco.

Adolescent mental health as a risk factor for adolescent smoking onset

Smoking continues to be a leading cause of preventable deaths and rates of trying cigarettes and progression to daily smoking among adolescents continues to remain high. A plethora of risk factors for smoking among adolescents has been addressed in the research literature. One that is gaining particular interest is the relationship between adolescent mental health and smoking (both initiation and progression). This paper reviews the evidence for adolescent mental health as a risk factor for cigarette smoking. We focus on the specific mental health conditions that have been more thoroughly addressed as possible risk factors in community-dwelling adolescents. We discuss the multiple hypotheses that have been posited as to the nature of the relationship between adolescent mental health and smoking, as well as detailing so called third factors that may account for the observed relationship. We highlight the contribution of the existing studies to the body of knowledge on this topic, as well as the limitations and open questions that remain as a result. We conclude with discussion of a broad research agenda going forward.

Smoking, parent smoking, depressed mood, and suicidal ideation in teens

OBJECTIVES

We address whether smoking is related to suicidal ideation in teens and whether there is evidence of a causal pathway.

METHODS

We use data from the 2002 National Annenberg Survey of Youth and employ multivariate logistic regression to model each teen's risk of suicidal ideation as a function of self-report of depressive symptoms, own smoking, parent smoking, and demographic and household income variables.

RESULTS

Individuals reporting depressive symptoms have an increased risk of suicidal ideation (odds ratio [OR] = 13.13; 95% CI = 5.98-28.81). Relative to teens who do not smoke and whose parents do not smoke, teens who smoke and do not have a parent who smokes have increased risk of suicidal ideation (OR = 8.10; 95% CI = 2.88-22.80), whereas those with a parent who smokes do not have a statistically significant increased risk of suicidal ideation regardless of teen smoking behavior.

CONCLUSION

Relative to teens who do not smoke and do not have parents who smoke, suicidal ideation risk is increased in teens who smoke only if they do not have a parent who smokes. We find evidence that the smoking and suicidal ideation of the teens is likely due to common psychosocial causes rather than a causal pathway from smoking to suicidal ideation.

Blunted opiate modulation of prolactin response in smoking men and women

Endogenous opioids are integral in modulating drug reward, but it is believed that these may act through several mechanisms including hypothalamic-pituitary-adrenocortical (HPA) and dopamine pathways. This study was developed to examine how nicotine dependence alters endogenous opioid regulation of prolactin response, a peripheral marker of dopaminergic activity. Smokers and nonsmokers completed two sessions during which placebo or 50mg of naltrexone was administered, using a double-blind, counterbalanced design. Blood samples and mood measures were obtained during a resting absorption period, after exposure to two noxious stimuli (cold pressor and thermal pain), and during an extended recovery period. Opioid blockade increased prolactin response, indicating an inhibitory effect of the endogenous opioid system on prolactin, possibly mediated by reduced stimulatory effects of dopamine on this hormone. These responses were attenuated in smokers relative to nonsmokers. There was also a gender disparity in prolactin response, with women showing a stronger response to endogenous opioid modification than men regardless of smoking status. The attenuated effects of opioid blockade may reflect dysregulated opiodergic and dopaminergic effects. Results extend previous reports showing blunted opioid regulation of the HPA response in dependent smokers.

Prenatal nicotine-exposure alters fetal autonomic activity and medullary neurotransmitter receptors: implications for sudden infant death syndrome

During pregnancy, exposure to nicotine and other compounds in cigarette smoke increases the risk of the sudden infant death syndrome (SIDS) two- to fivefold. Serotonergic (5-HT) abnormalities are found, in infants who die of SIDS, in regions of the medulla oblongata known to modulate cardiorespiratory function. Using a baboon model, we tested the hypothesis that prenatal exposure to nicotine alters 5-HT receptor and/or transporter binding in the fetal medullary 5-HT system in association with cardiorespiratory dysfunction. At 87 (mean) days gestation (dg), mothers were continuously infused with saline (n = 5) or nicotine (n = 5) at 0.5 mg/h. Fetuses were surgically instrumented at 129 dg for cardiorespiratory monitoring. Cesarean section delivery and retrieval of fetal medulla were performed at 161 (mean) dg for autoradiographic analyses of nicotinic and 5-HT receptor and transporter binding. In nicotine-exposed fetuses, high-frequency heart rate variability was increased 55%, possibly reflecting increases in the parasympathetic control of heart rate. This effect was more pronounced with greater levels of fetal breathing and age. These changes in heart rate variability were associated with increased 5-HT(1A) receptor binding in the raphé obscurus (P = 0.04) and increased nicotinic receptor binding in the raphé obscurus and vagal complex (P < 0.05) in the nicotine-exposed animals compared with controls (n = 6). The shift in autonomic balance in the fetal primate toward parasympathetic predominance with chronic exposure to nicotine may be related, in part, to abnormal 5-HT-nicotine alterations in the raphé obscurus. Thus increased risk for SIDS due to maternal smoking may be partly related to the effects of nicotine on 5-HT and/or nicotinic receptors.

The neuronal pathways mediating the behavioral and addictive properties of nicotine

This chapter considers the neurobiological mechanisms that are thought to mediate the reinforcing or rewarding properties of nicotine. It focuses on the data (derived principally from studies with experimental animals) showing that nicotine, like other drugs of dependence, stimulates the mesolimbic dopamine (DA) neurones that project to the nucleus accumbens and that these effects play a pivotal role in the biology underlying nicotine dependence. The reinforcing or rewarding properties of nicotine are thought to be associated particularly with the increase in DA overflow evoked in the shell subdivision of the accumbens. However, behavioural studies suggest that these properties of nicotine in experimental animals do not seem to be sufficiently potent to explain the powerful addiction to tobacco experienced by most habitual smokers. This chapter also considers the biological mechanisms that mediate the effects of cues and stimuli associated with the presentation of nicotine, which are thought to contribute significantly to the powerful addictive properties of tobacco smoke.

Smoking and suicide: a brief overview

This article provides a brief overview of the rationales, possible mechanisms and epidemiological data on the association of smoking, smoking cessation and cessation medications with suicide. Current smoking is reliably associated with suicide both in case-control and cohort studies. The three most plausible (but relatively untested) explanations for the association are that smokers have pre-existing conditions that increase their risk for suicide, smoking causes painful and debilitating conditions that might lead to suicide, and smoking decreases serotonin and monoamine oxidase levels. Stopping smoking appears to lead to major depression in some smokers; thus, it could induce suicide; however, smoking cessation has not been associated with suicide in the few studies available. Regulatory agencies have stated bupropion, rimonabant and varenicline appear to be associated with suicide; however, the data for these statements have not been presented in sufficient detail to assess their validity. Most prior data have come from post hoc analyses. Studies that a priori focus on understanding smoking and suicide are now needed.

Genetic variation in the serotonin pathway and smoking cessation with nicotine replacement therapy: new data from the Patch in Practice trial and pooled analyses

The serotonin pathway has been implicated in nicotine dependence and may influence smoking cessation. Therefore, 792 cigarette smokers from the Patch in Practice trial were genotyped for the tryptophan hydroxylase (TPH1 A779C), serotonin transporter (SLC6A45-HTTLPR), and 5-HT1A (HTR1A C-1019G) polymorphisms. Cox regression analysis did not demonstrate significant effects of any of the three genotypes on relapse to smoking: TPH1 (Reference AA; AC: hazard ratio (HR) 0.99, 95% confidence interval (CI) 0.78, 1.24, p=0.90; CC: HR 0.93, 95% CI 0.73, 1.18, p=0.55); 5-HTTLPR (Reference LL; SL: HR 1.01, 95% CI 0.85, 1.20, p=0.90; SS: HR 1.13, 95% CI 0.91, 1.39, p=0.27); HTR1A (Reference CC; CG: HR 1.04, 95% CI 0.86, 1.25, p=0.70; GG: HR 1.01, 95% CI 0.82, 1.24, p=0.93). Moreover, pooled analyses of data from all three extant pharmacogenetic NRT trials (N=1398) found no significant effect of 5-HTTLPR genotype on continuous abstinence at 12-week (Reference LL; SL: odds ratio (OR)=1.25, 95% CI 0.89, 1.74, p=0.19; SS: OR=1.31, 95% CI 0.86, 1.98, p=0.21) or 26-week follow-up (Reference LL; SL: OR=0.93, 95% CI 0.64, 1.33, p=0.68; SS: OR=1.00, 95% CI 0.63, 1.58, p=1.00). These data do not support a statistically or clinically significant moderating effect of these specific 5-HT pathway genetic variants on smoking cessation. However, the possibility remains that other variants in these or other 5-HT genes may influence NRT efficacy for smoking cessation in treatment seeking smokers.

Alpha4 containing nicotinic receptors are positioned to mediate postsynaptic effects on 5-HT neurons in the rat dorsal raphe nucleus

Nicotinic acetylcholine receptors containing the alpha4 and beta2 subunits constitute the most abundant high-affinity binding site of nicotine in the brain and are critical for the addictive qualities of nicotine. 5-HT neurotransmission is thought to be an important contributor to nicotine addiction. Therefore in this study it was examined how alpha4-containing receptors are positioned to modulate the function of 5-HT neurons using ultrastructural analysis of immunolabeling for the alpha4 receptor subunit in the dorsal raphe nucleus (DR), a primary source of forebrain 5-HT in the rat. Of 150 profiles labeled for the alpha4 subunit, 140 or 93% consisted of either soma or dendrites, these were often small-caliber (distal) dendrites <1.5 microm in diameter (63/150 or 42%). The majority (107/150 or 71%) of profiles containing labeling for alpha4 were dually labeled for the synthetic enzyme for 5-HT, tryptophan hydroxylase (TPH). Within dendrites immunogold labeling for alpha4 was present on the plasma membrane or near postsynaptic densities. However, labeling for alpha4 was commonly localized to the cytoplasmic compartment often associated with smooth endoplasmic reticulum, plausibly representing receptors in transit to or from the plasma membrane. Previous studies have suggested that nicotine presynaptically regulates activity onto 5-HT neurons, however alpha4 immunolabeling was detected in only 10 axons in the DR or 7% of profiles sampled. This finding suggest that alpha4 containing receptors are minor contributors to presynaptic regulation of synaptic activity onto 5-HT neurons, but rather alpha4 containing receptors are positioned to influence 5-HT neurons directly at postsynaptic sites.

Effects of cigarette smoking and family history of alcoholism on sweet taste perception and food cravings in women

BACKGROUND

Despite popular beliefs that smoking affects the sensitivity and liking of sweet-tasting foods and beverages, few psychophysical studies have examined this phenomenon and none have taken into account the individual's family history of alcoholism (FH+), a predictor of heightened sweet preferences.

METHODS

A within- and between-subjects study was conducted to determine the effect of both cigarette smoking and an acute exposure to nicotine on sweet taste sensitivity and preferences in women. Two groups were studied on 2 days separated by 1 week: women who were current smokers (n = 27, 18 were FH+) and those who never smoked in their lifetime (n = 22, 9 were FH+). Current smokers smoked nicotine-containing cigarettes during 1 test session and nicotine-free cigarettes during the other. The procedures were identical during both test sessions for the group of never smokers, with the exception that they did not smoke. Two-alternative staircase methods and forced-choice tracking procedures were used to assess sucrose thresholds and preferences, respectively, during both test session. Standardized questionnaires were administered to assess food cravings as well as smoking and alcohol usage and dependence. The Family Interview for Genetic Studies was used to detect alcoholism according to the DSM III criteria for family members up to second-degree relatives.

RESULTS

Acute exposure to nicotine did not affect sucrose detection thresholds or preferences, but smokers had significantly higher sucrose detection thresholds than never smokers. The greater the smoking dose in pack-years, the lower the sucrose sensitivity. Regardless of smoking status, women who were FH+ preferred significantly higher sucrose concentrations and craved sweets more often than women who were not.

CONCLUSIONS

Both smoking and having a family history of alcoholism had differential effects on sweet taste. Smoking was associated with decreased sweet taste sensitivity whereas having a family history of alcoholism was associated with heightened sweet preferences. These findings suggests that future research on the effects of smoking on food habits and cravings should take into account family history of alcoholism given its association with sweet liking and the increased likelihood to develop a tobacco disorder.

Common genetic factors for depression and cardiovascular disease

There is increasing knowledge regarding the considerable comorbidity between depression and cardiovascular disease, which are two of the most common disorders in developed countries. The associated vulnerability is not unidirectional, as the presence of cardiovascular disease can also influence mood states. Although this may be the result of psychological factors, common biological mechanisms, including genetic ones, are thought to be responsible for this interaction; we can thus question whether variations in genes could be predisposing factors. Regarding the multiple interactions in the mechanisms between depression and cardiovascular system disorders, eg, dysfunctions in the hypo-thalamic-pituitary-adrenocortical and sympathoadrenal axis and the response to stress, the importance of the sero-tonergic and immune systems, or the impact on the renin-angiotensin system, several candidate genes are being investigated. However, despite the interest in unraveling the potential susceptibility genes for both disorders, most available studies have so far dealt with the impact of polymorphisms in relation to either depression or cardiovascular disease. A few recent studies have now examined the effects of gene-gene or gene-environment interactions, and are investigating the impact of "depression-related" variants on cardiac response to stress. The first promising results were obtained with the serotonin transporter, and it may be hypothesized that this polymorphism interacts via the impact of the S allele on depression and via the effect of the L allele on platelet activation. However, the role played by various other candidate genes remains to be determined, especially regarding the question as to whether they are indicative of common pathophysiological mechanisms, or for identifying a subgroup of patients with somatic disorders that are more closely related to psychiatric symptoms.

Is the loudness dependence of auditory evoked potentials modulated by the selective serotonin reuptake inhibitor citalopram in healthy subjects?

The loudness dependence of auditory evoked potentials (LDAEP) has been discussed as a non-invasive in vivo marker of central serotonergic function. Evidence for this has been found in animal studies, but studies in humans provide less consistent results. In this study, the relationship between LDAEP and directly modulated central serotonergic activity in healthy subjects was investigated. In a single-blind cross-over design, the LDAEP of female participants (age: 24.0 +/- 2.3 years) was measured under two conditions: (1) infusion of 20 mg citalopram diluted in 250 ml 0.9% saline and (2) infusion of 250 ml 0.9% saline as placebo. LDAEP was measured at five different time points before, during and up to 60 min after drug/placebo administration and dipole source analysis was performed. The increase of the central serotonin activity in response to citalopram was not accompanied by a significant change of the LDAEP compared to the placebo condition. The result underlines that the acceptance of LDAEP as a marker of central serotonergic function still needs further discussion.

The Effects of Glutamate and GABA Receptor Antagonists on Nicotine-induced Neurotransmitter Changes in Cognitive Areas*

In the present study, we tested the effects of glutamate and GABA receptor antagonists on nicotine-induced neurotransmitter changes in the hippocampal (dorsal and ventral) and cortical (medial temporal and prefrontal) brain areas of conscious freely moving rats via microdialysis. Both the antagonists and nicotine were administered intracerebrally. The antagonists tested were NMDA, AMPA-kainate, and metabotropic glutamate receptor subtype antagonists (MK801, CNQX, and LY 341495, respectively) and GABA(A) and GABA(B) receptor subtype antagonists (bicuculline and hydroxysaclofen, respectively). We assayed nicotine-induced changes in dopamine (DA), norepinephrine (NE), serotonin (5-HT), and their metabolites. We found with the antagonists, both decreases and increases in nicotine-induced neurotransmitter responses. In the presence of nicotine all the antagonists (except LY 341495) caused a decrease in DA levels in the regions tested. NE levels were decreased in the cortex by all antagonists. In the hippocampus, GABA antagonists decreased NE levels, as did the metabotropic glutamate antagonist, LY 341495, while the other glutamate antagonists increased NE levels. The results of the 5-HT assay were more variable and dependent on the region and antagonist examined; increases were found slightly more often than decreases. The changes in metabolites were not often parallel with changes in their associated neurotransmitters, indicating that the antagonists also affect the metabolism of the neurotransmitters. The effect of the antagonists in the absence of nicotine was mostly to decrease the level of neurotransmitters, although increases were seen in a few cases. The results suggest that the excitatory glutamatergic- and inhibitory GABAergic-amino acid receptors are both involved in mediating nicotine-induced neurotransmitter responses, and their inhibitory or stimulatory effects are receptor subtype and brain region dependent.

Hypothalamic–Pituitary–Adrenocortical responses to psychological stress and risk for smoking relapse

Stress is a commonly reported precipitant of relapse to substance use. There is a growing recognition of the need to understand psychobiological alterations in the stress response among chronic drug users, and to determine how they may precipitate relapse. This paper focuses on the hypothalamic-pituitary-adrenocortical (HPA) response to stress among dependent smokers. Nicotine acutely activates the HPA axis, and increased HPA activity has been linked to attenuated CNS nicotinic receptor sensitivity. We will review a series of studies demonstrating that steep decline in cortisol concentrations during early abstinence and hyporesponsiveness to stress predict shorter time to relapse. Our studies show that hormonal associations with smoking relapse tend to be more consistent in men, while intensity of withdrawal symptoms tend to be consistent predictors of smoking relapse in women. We propose that perturbed HPA activity during early smoking abstinence exacerbate withdrawal symptoms and may contribute to the rapid relapse observed in the majority of smokers. Our results also reinforce the need for gender-specific investigation of mechanistic and interventional strategies to combat nicotine addiction.

The effects of cholinergic and dopaminergic antagonists on nicotine-induced cerebral neurotransmitter changes

In a continuing study of nicotine-induced mechanisms in brain areas associated with cognitive processes, the effects of cholinergic and dopaminergic antagonists on nicotine-induced changes in dopamine, norepinephrine, and serotonin were examined. These effects were measured via in vivo microdialysis in the dorsal and ventral hippocampus and in the prefrontal and medial temporal cortex of conscious, freely moving, adult male rats. Nicotine (0.3 mg/kg, free base) was administered subcutaneously and the antagonists were infused locally via the microdialysis probe. Nicotine alone induced an increase of dopamine and its metabolites in all areas, an increase of norepinephrine in the cortex, and an increase of the norepinephrine metabolite 4-hydroxy-3-methoxy-phenylglycol in all areas. Serotonin was decreased in the hippocampus and increased in the cortex. Nicotine-induced dopamine increases were inhibited by nicotinic (mecamylamine 100 microM, methyllycaconitine 500 microM), muscarinic (atropine 100 microM), and dopaminergic D1 (SCH23390 100 microM) and D2 (eticlopride 100 microM) antagonists, in the hippocampal and cortical areas. In the hippocampal areas, these antagonists had less significant effect on norepinephrine and serotonin. However, in the cortical areas, all antagonists inhibited the nicotine-induced increase of serotonin to varying degrees; and some, primarily nicotinic and dopamine D1 antagonists, inhibited the induced increase of norepinephrine. In the hippocampal and cortical areas, the mechanisms of nicotine-induced dopamine increase seem to be similar, but the mechanisms seem to be different for noradrenergic and serotonergic systems, as shown by the fact that nicotine induces no change in norepinephrine and a decrease in serotonin in the hippocampus, while it induces an increase in both in the cortex. Nicotine-induced dopamine release seems to be mediated, in part locally, by nicotinic and muscarinic receptors on dopaminergic cells. In contrast, nicotine's effect on norepinephrine and serotonin is at least partially mediated by initial changes at other than local sites, and through different receptors. Thus, the effects of nicotine and the mechanisms involved differ for different neurotransmitters and in different brain areas.

Adult neurogenesis: from precursors to network and physiology

The discovery that the adult mammalian brain creates new neurons from pools of stemlike cells was a breakthrough in neuroscience. Interestingly, this particular new form of structural brain plasticity seems specific to discrete brain regions, and most investigations concern the subventricular zone (SVZ) and the dentate gyrus (DG) of the hippocampal formation (HF). Overall, two main lines of research have emerged over the last two decades: the first aims to understand the fundamental biological properties of neural stemlike cells (and their progeny) and the integration of the newly born neurons into preexisting networks, while the second focuses on understanding its relevance in brain functioning, which has been more extensively approached in the DG. Here, we propose an overview of the current knowledge on adult neurogenesis and its functional relevance for the adult brain. We first present an analysis of the methodological issues that have hampered progress in this field and describe the main neurogenic sites with their specificities. We will see that despite considerable progress, the levels of anatomic and functional integration of the newly born neurons within the host circuitry have yet to be elucidated. Then the intracellular mechanisms controlling neuronal fate are presented briefly, along with the extrinsic factors that regulate adult neurogenesis. We will see that a growing list of epigenetic factors that display a specificity of action depending on the neurogenic site under consideration has been identified. Finally, we review the progress accomplished in implicating neurogenesis in hippocampal functioning under physiological conditions and in the development of hippocampal-related pathologies such as epilepsy, mood disorders, and addiction. This constitutes a necessary step in promoting the development of therapeutic strategies.

Cue reactivity in nicotine and tobacco dependence: a “multiple-action” model of nicotine as a primary reinforcement and as an enhancer of the effects of smoking-associated stimuli

The present paper proposes a model for the identification and the validation of brain processes and mechanisms underlying smokers' cue reactivity. Smoking behaviour is maintained by the reinforcing properties of nicotine, but it was also proposed that nicotine enhances the conditioned value of smoking and nicotine-associated stimuli. In fact, it is widely reported that the exposure of smokers to smoking/nicotine-associated stimuli induces cue reactivity, which is a vast array of physiological, psychological and behavioural responses. Imaging studies are revealing neuroanatomical correlates of cue reactivity in brain areas involved in motivational, emotional, cognitive processes and in their integration. Behavioural studies in laboratory animal models have shown analogies between the effects of nicotine-associated stimuli and cue reactivity effects in smokers. Lesion and mapping studies with nicotine reported brain activation patterns in cortico-limbic areas similarly to those obtained with imaging studies in humans. Although only limited studies have been done with nicotine-associated stimuli in animals, the identification of molecular mechanisms underlying other drugs of abuse-associated cue effect may help to propose potential common molecular mechanisms for nicotine cues. These findings suggest that smoking/nicotine-associated stimuli are processed at two levels: (i), bottom-up, automatic processing in a parallel fashion through ascendant pathways, to activate attentional functions; (ii), top-down, in a serial fashion from cortical areas, to modulate sensory inputs and motor control. It appears that nicotine increase information processing at both levels so as to establish and to amplify the conditioned value of smoking cues.

Psychobiological Theories of Smoking and Smoking Motivation

Abstract. Theories of smoking have been developed about the conditions and causes of smoking as well as for explaining its maintenance. Moreover, factors of smoking motivation have been identified, which describe incentives to smoke and types of smoking behavior. The most frequently reported motives are psychosocial smoking, sensorimotor smoking, indulgent smoking, stimulation smoking, sedation smoking, dependent smoking, and automatic smoking. In the first phase after the start of smoking, psychosocial smoking is the dominating motive, which is best represented by theories of social psychology. Sensorimotor smoking may be best explained by theories of classical and operant conditioning. Indulgent smoking (= smoking for pleasure) may be explained by neurochemical theories and by the neurobiological theories of dependence emphasizing nicotine-induced activation of mesolimbic dopaminergic reinforcement. Stimulation smoking and sedation smoking are related to arousal models. Moreover, sedation smoking is also explained by aspects of reducing negative affect (as claimed by theories of affect regulation) and by biochemical theories emphasizing serotonergic mechanisms in modulating anxiety as well as by theories of dependence. Dependent smoking, which is mostly based on negative reinforcement (suppression of withdrawal symptoms) may be explained by neurochemical theories as well as by neurobiological theories of psychological and physical dependence explaining blunted dopaminergic and serotonergic responsivity as due to desensitization of respective receptors. Also automatic smoking may be explained by processes of habit learning and neurobiological theories of dependence. Finally, personality theories have been applied to all of these smoking motives.

Selective stimulation of serotonin2c receptors blocks the enhancement of striatal and accumbal dopamine release induced by nicotine administration

The effects of acute and repeated nicotine administration on the extracellular levels of dopamine (DA) in the corpus striatum and the nucleus accumbens were studied in conscious, freely moving rats by in vivo microdialysis. Acute intraperitoneal (i.p.) injection of nicotine (1 mg/kg) increased DA outflow both in the corpus striatum and the nucleus accumbens. Repeated daily injection of nicotine (1 mg/kg, i.p.) for 10 consecutive days caused a significant increase in basal DA outflow both in the corpus striatum and the nucleus accumbens. Acute challenge with nicotine (1 mg/kg, i.p.) in animals treated repeatedly with this drug enhanced DA extracellular levels in both brain areas. However, the effect of nicotine was potentiated in the nucleus accumbens, but not in the corpus striatum. To test the hypothesis that stimulation of 5-HT (5-hydroxytryptamine, serotonin)(2C) receptors could affect nicotine-induced DA release, the selective 5-HT(2C) receptor agonist RO 60-0175 was used. Pretreatment with RO 60-0175 (1 and 3 mg/kg, i.p.) dose-dependently prevented the enhancement in DA release elicited by acute nicotine in the corpus striatum, but was devoid of any significant effect in the nucleus accumbens. RO 60-0175 (1 and 3 mg/kg, i.p.) dose-dependently reduced the stimulatory effect on striatal and accumbal DA release induced by an acute challenge with nicotine (1 mg/kg, i.p.) in rats treated repeatedly with this alkaloid. However, only the effect of 3 mg/kg RO 60-0175 reached statistical significance. The inhibitory effect of RO 60-0175 on DA release induced by nicotine in the corpus striatum and the nucleus accumbens was completely prevented by SB 242084 (0.5 mg/kg, i.p.) and SB 243213 (0.5 mg/kg, i.p.), two selective antagonists of 5-HT(2C) receptors. It is concluded that selective activation of 5-HT(2C) receptors can block the stimulatory action of nicotine on central DA function, an effect that might be relevant for the reported antiaddictive properties of RO 60-0175.

Tobacco use is associated with reduced central serotonergic neurotransmission in type 1 alcohol-dependent individuals

BACKGROUND

Reduced central serotonergic neurotransmission in alcohol dependence may be attributed to the effects of cigarette smoking (and possibly more specifically to nicotine) rather than to alcoholism or its subtypes. The aim of the present study was therefore to compare central serotonergic neurotransmission in tobacco-using (cigarette smokers and users of smokeless tobacco, i.e., snuffers) alcohol-dependent individuals to that of tobacco-nonusing alcohol-dependent individuals.

METHODS

The central serotonergic neurotransmission was assessed by the prolactin (PRL) response to the serotonin-releasing agent D-fenfluramine (30 mg orally). Male subjects (n = 37) aged 20-65 years were recruited for this purpose. They were all type 1 alcohol-dependent individuals and had ended their alcohol intake the day before the D-fenfluramine challenge test.

RESULTS

There was no difference in baseline PRL concentrations between tobacco-using (n = 18) and tobacco-nonusing (n = 19) alcohol-dependent individuals. On the other hand, the maximum PRL response after D-fenfluramine was significantly lower in the tobacco-using group as compared to the tobacco-nonusing individuals.

CONCLUSION

Whether the reduction in central serotonergic neurotransmission in tobacco-using alcohol-dependent individuals is pre-existing or a result of tobacco use remains to be elucidated.