Smoking and schizophrenia in population cohorts of Swedish women and men: a prospective co-relative control study

Cross-ancestry genetic investigation of schizophrenia, cannabis use disorder, and tobacco smoking

Individuals with schizophrenia frequently experience co-occurring substance use, including tobacco smoking and heavy cannabis use, and substance use disorders. There is interest in understanding the extent to which these relationships are causal, and to what extent shared genetic factors play a role. We explored the relationships between schizophrenia (Scz; European ancestry N = 161,405; African ancestry N = 15,846), cannabis use disorder (CanUD; European ancestry N = 886,025; African ancestry N = 120,208), and ever-regular tobacco smoking (Smk; European ancestry N = 805,431; African ancestry N = 24,278) using the largest available genome-wide studies of these phenotypes in individuals of African and European ancestries. All three phenotypes were positively genetically correlated (rgs = 0.17-0.62). Genetic instrumental variable analyses suggested the presence of shared heritable factors, but evidence for bidirectional causal relationships was also found between all three phenotypes even after correcting for these shared genetic factors. We identified 327 pleiotropic loci with 439 lead SNPs in the European ancestry data, 150 of which were novel (i.e., not genome-wide significant in the original studies). Of these pleiotropic loci, 202 had lead variants which showed convergent effects (i.e., same direction of effect) on Scz, CanUD, and Smk. Genetic variants convergent across all three phenotypes showed strong genetic correlations with risk-taking, executive function, and several mental health conditions. Our results suggest that both shared genetic factors and causal mechanisms may play a role in the relationship between CanUD, Smk, and Scz, but longitudinal, prospective studies are needed to confirm a causal relationship.

Association between electronic nicotine product use and subsequent first episode psychosis

Tobacco use has been established as a possible risk factor for psychosis, but the effect of electronic nicotine delivery systems (ex. nicotine vapes) has not been independently established. Using the Population Assessment of Tobacco and Health study, we found that use of electronic nicotine products was significantly associated with later first episode psychosis after controlling for substance use and other confounders, and that this relationship was only significant among the heaviest users (>20 puffs/day). Given the rapid rise in electronic nicotine products use, clinicians and public health professionals should consider potential impacts and closely monitor trends in the coming years.

Smoking affects symptom improvement in schizophrenia: a prospective longitudinal study of male patients with first-episode schizophrenia

Patients with schizophrenia (SCZ) smoke up to three times more than general people. However, there are conflicting results regarding the relationship between tobacco smoke and clinical symptom severity in SCZ. The aim of this study was to assess the impact of smoking on clinical symptoms after antipsychotic treatment in a 12-week cohort study after controlling for confounding factors. One hundred and forty-five male patients with drug-naïve first-episode (DNFE) SCZ received antipsychotic monotherapy for 12 weeks. Symptom severity was assessed at baseline and at week 12 by the Positive and Negative Syndrome Scale (PANSS). We found no differences in clinical symptoms among male smokers with SCZ compared with male nonsmokers. However, male smokers showed greater improvement in negative symptoms after 12 weeks of treatment, controlling for age, years of education, onset age, and baseline body mass index (BMI). Our study showed that after 12 weeks of treatment with antipsychotics, male smokers showed greater improvement in negative symptoms than male nonsmokers.

Schizophrenia mediating the effect of smoking phenotypes on antisocial behavior: A Mendelian randomization analysis

AIMS

Previous studies have indicated that smoking is linked to an increased risk of developing schizophrenia, and that individuals with schizophrenia are more prone to engaging in antisocial behavior. However, the causal effects of smoking behaviors on antisocial behavior and the potential mediating role of schizophrenia remains largely unclear.

METHODS

In the present study, using the summary data from genome wide association studies of smoking phenotypes (N = 323,386-805,431), schizophrenia (Ncases = 53,386, Ncontrols = 77,258), and antisocial behavior (N = 85,359), we assessed bidirectional causality between smoking phenotypes and schizophrenia by the Mendelian randomization (MR) approach. Using a two-step MR approach, we further examined whether causal effects of smoking phenotypes/schizophrenia on antisocial behavior were mediated by schizophrenia/smoking phenotypes.

RESULTS

The results showed that smoking initiation (SmkInit) and age of smoking initiation (AgeSmk) causally increase the risk of schizophrenia (SmkInit: OR = 2.06, 95% CI = 1.77-2.39, p = 4.36 × 10-21 ; AgeSmk: OR = 0.32, 95% CI = 0.16-0.62, p = 8.11 × 10-4 , Bonferroni corrected). However, there was no causal effect that liability to schizophrenia leads to smoking phenotypes. MR evidence also revealed causal influences of SmkInit and the amount smoked (CigDay) on antisocial behavior (SmkInit: OR = 1.28, 95% CI = 1.17-1.41, p = 2.53 × 10-7 ; CigDay: OR = 1.16, 95% CI = 1.06-1.27, p = 1.60 × 10-3 , Bonferroni corrected). Furthermore, the mediation analysis indicated that the relationship between SmkInit and antisocial behavior was partly mediated by schizophrenia (mediated proportion = 6.92%, 95% CI = 0.004-0.03, p = 9.66 × 10-3 ).

CONCLUSIONS

These results provide compelling evidence for taking smoking interventions as a prevention strategy for schizophrenia and its related antisocial behavior.

Cross-ancestry genetic investigation of schizophrenia, cannabis use disorder, and tobacco smoking

Individuals with schizophrenia frequently experience co-occurring substance use, including tobacco smoking and heavy cannabis use, and substance use disorders. There is interest in understanding the extent to which these relationships are causal, and to what extent shared genetic factors play a role. We explored the relationships between schizophrenia (Scz), cannabis use disorder (CanUD), and ever-regular tobacco smoking (Smk) using the largest available genome-wide studies of these phenotypes in individuals of African and European ancestries. All three phenotypes were positively genetically correlated (rgs = 0.17 - 0.62). Causal inference analyses suggested the presence of horizontal pleiotropy, but evidence for bidirectional causal relationships was also found between all three phenotypes even after correcting for horizontal pleiotropy. We identified 439 pleiotropic loci in the European ancestry data, 150 of which were novel (i.e., not genome-wide significant in the original studies). Of these pleiotropic loci, 202 had lead variants which showed convergent effects (i.e., same direction of effect) on Scz, CanUD, and Smk. Genetic variants convergent across all three phenotypes showed strong genetic correlations with risk-taking, executive function, and several mental health conditions. Our results suggest that both horizontal pleiotropy and causal mechanisms may play a role in the relationship between CanUD, Smk, and Scz, but longitudinal, prospective studies are needed to confirm a causal relationship.

New medications development for smoking cessation

Diseases associated with nicotine dependence in the form of habitual tobacco use are a major cause of premature death in the United States. The majority of tobacco smokers will relapse within the first month of attempted abstinence. Smoking cessation agents increase the likelihood that smokers can achieve long-term abstinence. Nevertheless, currently available smoking cessation agents have limited utility and fail to prevent relapse in the majority of smokers. Pharmacotherapy is therefore an effective strategy to aid smoking cessation efforts but considerable risk of relapse persists even when the most efficacious medications currently available are used. The past decade has seen major breakthroughs in our understanding of the molecular, cellular, and systems-level actions of nicotine in the brain that contribute to the development and maintenance of habitual tobacco use. In parallel, large-scale human genetics studies have revealed allelic variants that influence vulnerability to tobacco use disorder. These advances have revealed targets for the development of novel smoking cessation agents. Here, we summarize current efforts to develop smoking cessation therapeutics and highlight opportunities for future efforts.

Current (but not ex) cigarette smoking is associated with worse cognitive performances in schizophrenia: results from the FACE-SZ cohort

BACKGROUND

Tobacco use is common in subjects with schizophrenia (SZ) and has sometimes been associated with better functioning in short-term studies. Only few studies embrace an extensive examination of tobacco influence on clinical, cognitive and therapeutic characteristics in stabilized SZ outpatients. The objective of the present study was to assess the association between cognitive performances and smoking status in SZ subjects.

METHODS

In total, 1233 SZ participants (73.9% men, mean age 31.5) were included and tested with a comprehensive battery. Tobacco status was self-declared (never-, ex-, or current smokers). Multivariable analyses including principal component analyses (PCA) were used.

RESULTS

In total, 53.7% were smokers with 33.7% of them nicotine-dependent. Multiple factor analysis revealed that current tobacco smoking was associated with impaired general intellectual ability and abstract reasoning (aOR 0.60, 95% IC 0.41-0.88, p = 0.01) and with a lifetime alcohol use disorder (p = 0.026) and a lifetime cannabis use disorder (p < 0.001). Ex- and never-smokers differed for age, mean outcome, cannabis history and medication [ex-smokers being older (p = 0.047), likely to have higher income (p = 0.026), a lifetime cannabis use disorder (p < 0.001) and higher CPZeq doses (p = 0.005)]. Premorbid IQ in the three groups significantly differed with, from higher to lower: ex-smokers, never-smoker, current smokers (all p < 0.001).

CONCLUSIONS

This study is the largest to date providing strong evidence that chronic smoking is associated with cognitive impairment in SZ, arguing against the self-medication hypothesis as a contributor to the high prevalence of smoking in SZ. Ex-smokers may also represent a specific subgroup. Longitudinal studies are warranted to determine the developmental impact of tobacco on neurocognition.

Genetic susceptibility for schizophrenia after adjustment by genetic susceptibility for smoking: implications in identification of risk genes and genetic correlation with related traits

BACKGROUND

Prevalence of smoking in schizophrenia (SCZ) is larger than in general population. Genetic studies provided some evidence of a causal effect of smoking on SCZ. We aim to characterize the genetic susceptibility to SCZ affected by genetic susceptibility to smoking.

METHODS

Multi-trait-based conditional and joint analysis was applied to the largest European SCZ genome-wide association studies (GWAS) to remove genetic effects on SCZ driven by smoking, estimated by generalized summary data-based Mendelian randomization. Enrichment analysis was performed to compare original v. conditional GWAS. Change in genetic correlation between SCZ and relevant traits after conditioning was assessed. Colocalization analysis was performed to identify specific loci confirming general findings.

RESULTS

Conditional analysis identified 19 new risk loci for SCZ and 42 lost loci whose association with SCZ may be partially driven by smoking. These results were strengthened by colocalization analysis. Enrichment analysis indicated a higher association of differentially expressed genes at prenatal brain stages after conditioning. Genetic correlation of SCZ with substance use and dependence, attention deficit-hyperactivity disorder, and several externalizing traits significantly changed after conditioning. Colocalization of association signal between SCZ and these traits was identified for some of the lost loci, such as CHRNA2, CUL3, and PCDH7.

CONCLUSIONS

Our approach led to identification of potential new SCZ loci, loci partially associated to SCZ through smoking, and a shared genetic susceptibility between SCZ and smoking behavior related to externalizing phenotypes. Application of this approach to other psychiatric disorders and substances may lead to a better understanding of the role of substances on mental health.

Prevalence of tobacco smoking in people at clinical high-risk for psychosis: Systematic review and meta-analysis

Several hypotheses have been proposed to explain why individuals with psychosis consume more tobacco compared with the general population, but the reasons remain unclear. The phases predating the onset of psychosis could provide an interesting framework to clarify this association. The aim of this systematic review and meta-analysis is to provide an updated and comprehensive synthesis of the association between tobacco smoking and Clinical High Risk for Psychosis (CHRP) status. We performed a multistep systematic PRISMA/MOOSE-compliant electronic search for articles published from inception until October 1st, 2021. Web of Science was searched, complemented by a manual search of original articles reporting the outcome of tobacco consumption (defined as the number of individuals which were smoking tobacco at baseline) in a group of CHR-P patients versus healthy controls (HC). We employed quality assessment of the included studies with Newcastle Ottawa Scale (NOS). The effect size for the primary outcome was the odds ratio (OR) of smoking tobacco in CHR-P samples vs HC. We performed a random-effects model meta-analysis, assessment of heterogeneity with I² index, sensitivity analyses excluding one study at a time for primary outcome, meta-regressions with four independent moderators (mean age, female ratio, sample size, NOS) and assessment of publication bias with funnel plot and Egger's test. We included 21 independent articles, totalling 2018 CHR-P individuals (mean age of 21.35 ± 2.91 years and average female ratio of 41 ± 7 %) and 1160 HC (mean age of 22.42 ± 3.70 years and average female ratio of 45 ± 11 %). The NOS score was 6.52 ± 1.25 (range from 0 to 9). The OR of smoking status was 2.22 (95%CI 1.74-2.84, p < 0.01). Heterogeneity (I²) was 24.09 (p = 0.16). Sensitivity analyses, removing one study at a time, revealed the robustness of our main finding. Meta-regressions did not reveal any significant association between the moderators and the main outcome. Visual inspection of the funnel plot and Egger's test did not reveal evident publication bias. Our main finding of an increased OR of smokers in the CHR-P individuals compared to healthy controls corroborates the accumulation of unhealthy lifestyles in this vulnerable group. This does not demonstrate any causal association between tobacco smoking and incidence of psychosis, which should be investigated in future prospective cohorts. In conclusion, the window of opportunity represented by CHR-P status should involve more efficient physical health screening and better investigating the aetiological impact of smoking in the development of psychosis.

Smoking Habits and Attitudes toward Smoking in Patients with Severe Mental Illness in Residential Facilities in Insular Greece

Smoking may contribute to increased cardiovascular morbidity and mortality in patients with schizophrenia spectrum disorders. The objective of the present study is to explore the attitudes toward smoking in patients with severe mental illness in residential rehabilitation facilities in insular Greece. The patients (n = 103) were studied with the use of a questionnaire based on a semi-structured interview. Most of the participants (68.3%) were current regular smokers, had been smoking for 29 years and started smoking at an early age. The majority (64.8%) reported having tried to quit smoking in the past, and only half had been advised by a physician to quit. The patients agreed on the rules for smoking and believed that the staff should avoid smoking in the facility. The years of smoking were statistically significantly correlated to the educational level and the treatment with antidepressant medication. A statistical analysis showed that longer stay period in the facilities correlates with current smoking, an effort to quit and increased belief that smoking causes harm to health. Further research on the attitudes of patients in residential facilities toward smoking is needed, which could guide interventions for smoking cessation and should be assumed by all health professionals who are involved in the care of those patients.

Substance use Specificities in Women with Psychosis: A Critical Review

BACKGROUND

Women with schizophrenia or other psychotic disorders differ from male patients in many respects, including psychopathology, prognosis, disease course, and substance use comorbidities. Most studies performed to date to investigate the association between drug use and psychosis have not evaluated gender differences, although this has started to change in recent years.

METHODS

We briefly summarize the available evidence on gender differences in drug use and substance use disorders (SUD) in psychotic patients during the early phases of the psychotic illness and during the course of schizophrenia.

RESULTS

Substance use and SUD are both less prevalent in women, both in the general population and at all phases of the psychotic spectrum. Some studies suggest that SUD may be under diagnosed in female patients, in part due to their more vulnerable profile. Substance use, especially cannabis, may more negatively impact females, especially on the disease course and prognosis. The available data suggest that it may be more difficult to treat SUD in female patients with schizophrenia, which could negatively impact prognosis.

CONCLUSION

Women with concomitant psychotic illness and SUD comprise a highly vulnerable subgroup. This should be considered when selecting the treatment approach, especially in the early phases of the illness, to ensure better outcomes.

Prevalence and severity of tobacco use and access to tobacco cessation among tertiary care psychiatric in-patients in India

Background

Rates of smoking in persons with mental illness are reported to be two times higher than those without mental illness in developed countries. We aimed to examine the prevalence and severity of tobacco use, and access to tobacco cessation services among tertiary care psychiatric in-patients in India.

Methods

In this cross-sectional study, 500 consecutive adult in-patients in tertiary care with ICD 10 diagnoses, F20-59, were administered a sociodemographic and clinical proforma, Clinical Global Impression-Severity scale, Fagerstrom Test for Nicotine Dependence, Tobacco Craving Questionnaire, Reasons for quitting questionnaire, and Smoke Scale-Adults. Urine cotinine levels were estimated in the last 100 patients. Details of tobacco use and cessation interventions provided were obtained.

Results

Overall prevalence of current tobacco use was 34.00%; 34.3%, 32.6%, 43.6%, and 16.7% in patients of F20-29, F30-39, F40-49, and F50-59 categories, respectively. Males used tobacco products at a significantly higher rate (44.85% vs. 17.58% in females) and were highly dependent. Smokeless tobacco use was reported in 20.5% and 18% of female patients with F20-29 and F30-39 diagnoses, respectively. More than half of the tobacco users were not asked about tobacco use and 89.4% of the users were provided no prior assistance for cessation at the time of assessment. Urinary cotinine levels were significantly greater for those who use smokeless forms than smokers or dual users.

Conclusions

Nearly a third of psychiatric in-patients are current users of tobacco. Moderate to severe tobacco dependence was observed across psychiatric diagnoses. The assessment and interventions provided were suboptimal.

Demographics, clinical characteristics and cognitive symptoms of heavy smokers and non-heavy smokers in Chinese male patients with chronic schizophrenia

Many studies have shown a high smoking rate and cognitive impairment in patients with schizophrenia. The effects of smoking and nicotine intake on cognitive function in schizophrenia are still controversial. In this study, we divided patients into heavy smoking and non-heavy smoking groups and compared the clinical characteristics and cognitive symptoms between the two groups in Chinese male patients with schizophrenia. A total of 154 heavy smoking patients and 372 non-heavy smoking patients were recruited. They completed a detailed questionnaire including general and socio-demographic data. Positive and Negative Syndrome Scale (PANSS) was rated for psychopathology. The Fagerstrom Test for Nicotine Dependence (FTND) was used to assess the degree of nicotine dependence. Heavy smokers were younger, started smoking earlier and had a higher FTND total score than non-heavy smoking patients. Moreover, we found that heavy smokers had significantly lower negative symptom scores and cognitive factor scores than non-heavy smokers. Logistic regression analysis showed that cognitive factor score and age of initial smoking were significantly associated with heavy smoking. Linear regression analysis showed that cognitive factor score, age of initial smoking and dose of antipsychotics were significant predictors of the amount of smoking. Our findings suggest that there are significant differences in some demographic and clinical variables between heavy and non-heavy smokers in Chinese male patients with chronic schizophrenia. Moreover, heavy smokers have less cognitive symptoms, suggesting that heavy smoking may be beneficial for cognition of patients with schizophrenia.

Smoking in early adulthood is prospectively associated with prescriptions of antipsychotics, mood stabilizers, antidepressants and anxiolytics

BACKGROUND

Whether smoking should be regarded as a risk factor for mental disorders remains unresolved. Prescribed psychotropic drugs can be used as indications for mental disorders. We investigated how smoking was prospectively related to prescription of antipsychotics, mood stabilizers, antidepressants, and anxiolytics.

METHODS

Information about smoking, including the Fagerström Test for Nicotine Dependence, and relevant confounders, were obtained from the population-based Young in Norway Study (N = 2602), with four data collection waves between 1992 and 2006. These survey data were linked with information on prescriptions for psychotropic drugs from the comprehensive, nationwide Norwegian Prescription Database from 2007 to 2015.

RESULTS

Daily smoking with high dependence in 2006 at age 28.5 (s.d. = 2.0) was associated with filling prescriptions of antipsychotics (OR, 6.57, 95% CI 2.19-19.70, p = 0.001), mood stabilizers (OR, 7.11, 95% CI 2.51-20.15, p < 0.001) and antidepressants (OR, 1.91, 95% CI 1.13-3.23, p = 0.016) 1-9 years later. Associations remained significant after adjustment for a variety of potential confounders measured before the assessment of smoking, including sociodemographic background, conduct problems, cannabis use, mental distress, and previous prescriptions for psychotropic medications. The association between smoking and prescription of anxiolytics was weaker and more unstable.

CONCLUSIONS

In this study of young adults, daily smoking with high dependence was associated with later prescriptions of antipsychotics, mood stabilizers and antidepressants, indicating smoking as a risk factor for mental disorders treated with these drugs.

Evaluation of the causal relationship between smoking and schizophrenia in East Asia

Cigarette smoking has been suggested to be associated with the risk of schizophrenia in observational studies. A significant causal effect of smoking on schizophrenia has been reported in European populations using the Mendelian randomization approach; however, no evidence of causality was found in participants from East Asia. Using Taiwan Biobank (TWBB), we conducted genome-wide association studies (GWAS) to identify susceptibility loci for smoking behaviors, including smoking initiation (N = 79,989) and the onset age (N = 15,582). We then meta-analyzed GWAS from TWBB and Biobank Japan (BBJ) with the total sample size of 245,425 for smoking initiation and 46,000 for onset age of smoking. The GWAS for schizophrenia was taken from the East Asia Psychiatric Genomics Consortium, which included 22,778 cases and 35,362 controls. We performed a two-sample Mendelian randomization to estimate the causality of smoking behaviors on schizophrenia in East Asia. In TWBB, we identified one locus that met genome-wide significance for onset age. In a meta-analysis of TWBB and BBJ, we identified two loci for smoking initiation. In Mendelian randomization, genetically predicted smoking initiation (odds ratio (OR) = 4.00, 95% confidence interval (CI) = 0.89–18.01, P = 0.071) and onset age (OR for a per-year increase = 0.96, 95% CI = 0.91–1.01, P = 0.098) were not significantly associated with schizophrenia; the direction of effect was consistent with European Ancestry samples, which had higher statistical power. These findings provide tentative evidence consistent with a causal role of smoking on the development of schizophrenia in East Asian populations.

Investigating the reciprocal temporal relationships between tobacco consumption and psychological disorders for youth: an international review

OBJECTIVE

To investigate reciprocal temporal relationships between tobacco consumption and psychological disorders for youth.Design: Review DATA SOURCES: Five databases (PubMed, Embase, Scopus, CINAHL and PsycINFO) on 26 September 2019 and updated on 11 May 2021, indexing tobacco, mental illness and longitudinal.Study selection: Methods used consensus and multiple reviewers.

INTERVENTIONS

Cohort studies (n=49) examining tobacco and selected psychological disorders (depression, anxiety, bipolar, psychosis, borderline personality disorder) among youth, and systematic reviews (n=4) of these relationships met inclusion criteria.

PRIMARY AND SECONDARY OUTCOME MEASURES

Effect of tobacco on psychological disorders and effect of psychological disorders on tobacco.

DATA EXTRACTION AND SYNTHESIS

Independent extraction by the first author and checked by final author. Joanna Briggs Institute Critical Appraisal Tools were used for all studies.Included studies had moderate-to-high appraisal scores. We synthesised findings using vote counting for effect direction and descriptive data.

RESULTS

Fifty-three studies were included in the review. Thirteen of 15 studies showed a positive effect direction of tobacco on depression (p<0.001). Six of 12 studies showed a positive effect direction of depression on tobacco (p=0.016). Six of eight studies showed a positive effect direction of tobacco on anxiety (p=0.016). Eleven of 18 studies showed a positive effect direction of anxiety on tobacco (p=0.003). No effect between tobacco and bipolar, or tobacco and psychosis was found. No studies examined tobacco and borderline personality disorder.

CONCLUSIONS

Reciprocal relationships existed between tobacco and both depression and anxiety for youth, though causality is unconfirmed. No positive effect direction was found between tobacco and psychosis, perhaps because nicotine has conflicting effects on psychosis. For other relationships examined, evidence was weak because of low number of studies. More research to inform prevention and early intervention is needed.

PROSPERO REGISTRATION NUMBER

CRD42020150457.

Multifactorial Causes of Paranoid Schizophrenia With Auditory-Visual Hallucinations in a 31-Year-Old Male With History of Traumatic Brain Injury and Substance Abuse

Schizophrenia is a chronic psychiatric disorder that classically presents with distortions of thought, behavior, and perceptions that are often misdiagnosed. One difficulty in diagnosing schizophrenia is due to its phenotypically heterogeneous condition that can be precipitated by a combination of genetic, epigenetic, and environmental factors. The prevalence of schizophrenia is roughly 1%, but it is often misdiagnosed. Possible differential diagnoses include depression or bipolar disorder with psychosis, psychosis due to a medical condition, schizotypal and schizoid personality disorders, and neurocognitive disorders. 

In this case report, a 31-year-old male presents with thoughts of suicide following a recent exacerbation of his hallucinations. On presentation, the patient presented with a historical diagnosis of “paranoid schizophrenia” as well as a history of traumatic brain injury (TBI), poly-substance use disorder, and a family history of schizophrenia. This case serves to highlight the difficulties of making an accurate diagnosis and providing evidenced-based treatment.

Portable Neuroimaging-Guided Noninvasive Brain Stimulation of the Cortico-Cerebello-Thalamo-Cortical Loop—Hypothesis and Theory in Cannabis Use Disorder

Background: Maladaptive neuroplasticity-related learned response in substance use disorder (SUD) can be ameliorated using noninvasive brain stimulation (NIBS); however, inter-individual variability needs to be addressed for clinical translation. Objective: Our first objective was to develop a hypothesis for NIBS for learned response in SUD based on a competing neurobehavioral decision systems model. The next objective was to develop the theory by conducting a computational simulation of NIBS of the cortico-cerebello-thalamo-cortical (CCTC) loop in cannabis use disorder (CUD)-related dysfunctional “cue-reactivity”—a construct closely related to “craving”—that is a core symptom. Our third objective was to test the feasibility of a neuroimaging-guided rational NIBS approach in healthy humans. Methods: “Cue-reactivity” can be measured using behavioral paradigms and portable neuroimaging, including functional near-infrared spectroscopy (fNIRS) and electroencephalogram (EEG) metrics of sensorimotor gating. Therefore, we conducted a computational simulation of NIBS, including transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS) of the cerebellar cortex and deep cerebellar nuclei (DCN) of the CCTC loop for its postulated effects on fNIRS and EEG metrics. We also developed a rational neuroimaging-guided NIBS approach for the cerebellar lobule (VII) and prefrontal cortex based on a healthy human study. Results: Simulation of cerebellar tDCS induced gamma oscillations in the cerebral cortex, while transcranial temporal interference stimulation induced a gamma-to-beta frequency shift. A preliminary healthy human study (N = 10) found that 2 mA cerebellar tDCS evoked similar oxyhemoglobin (HbO) response in the range of 5 × 10⁻⁶ M across the cerebellum and PFC brain regions (α = 0.01); however, infra-slow (0.01–0.10 Hz) prefrontal cortex HbO-driven phase–amplitude-coupled (PAC; 4 Hz, ±2 mA (max)) cerebellar tACS evoked HbO levels in the range of 10⁻⁷ M that were statistically different (α = 0.01) across these brain regions. Conclusion: Our healthy human study showed the feasibility of fNIRS of cerebellum and PFC and closed-loop fNIRS-driven ctACS at 4 Hz, which may facilitate cerebellar cognitive function via the frontoparietal network. Future work needs to combine fNIRS with EEG for multi-modal imaging for closed-loop NIBS during operant conditioning.

Alcohol use disorder and non-fatal suicide attempt: findings from a Swedish National Cohort Study

BACKGROUND AND AIMS

Alcohol use disorder (AUD) is associated with increased risk of non-fatal suicide attempt. We aimed to measure the strength and mechanistic nature of the association between AUD and increased suicide attempt and determine any causal pathways and/or shared risk factors.

DESIGN

We used Cox proportional hazards models in population-level and co-relative analyses to evaluate the risk of first non-fatal suicide attempt as a function of previous AUD.

SETTING AND PARTICIPANTS

We used continuously updated longitudinal nationwide Swedish registry data on native Swedes born from 1950 to 1970 (n = 2 229 619) and followed from age 15 until 2012.

MEASUREMENTS

AUD and suicide attempt were identified using International Classification of Diseases (ICD)-8, ICD-9, and ICD-10 codes. AUD was also identified using pharmacy and criminal records. Genetic and family environmental risks were derived based on relatedness via the Multi-Generation Register and shared residency via the Population and Housing Census and the Total Population Register.

FINDINGS

AUD was robustly associated with suicide attempt in crude models (hazard ratio [HR] = 15.24 [95% CI: 14.92, 15.56]). In models adjusted for sociodemographic factors and psychiatric comorbidity, the association was attenuated: for women, HRs declined gradually across time, ranging from 5.55 (3.72, 8.29) during the observation period that ranged from age 15 to 19 years to 1.77 (1.65, 1.90) at age 40 or older. For men, the corresponding figures were 6.12 (4.07, 9.19) and 1.83 (1.72, 1.94); in contrast to women, risk of suicide attempt among men increased from age 15 to 29 before declining. In co-relative models, a residual association remained, consistent with a causal path from AUD to suicide attempt.

CONCLUSIONS

In Sweden, alcohol use disorder appears to be an important predictor of suicide attempt even in the context of other psychiatric disorders. The observed association is likely the result of features that jointly impact risk of alcohol use disorder and suicide attempts (genetic liability, psychiatric illness, and childhood stressors) and a potentially causal pathway, acting independently or in conjunction with one another.

A polygenic approach to the association between smoking and schizophrenia

Smoking prevalence in schizophrenia is considerably larger than in general population, playing an important role in early mortality. We compared the polygenic contribution to smoking in schizophrenic patients and controls to assess if genetic factors may explain the different prevalence. Polygenic risk scores (PRSs) for smoking initiation and four genetically correlated traits were calculated in 1108 schizophrenic patients (64.4% smokers) and 1584 controls (31.1% smokers). PRSs for smoking initiation, educational attainment, body mass index and age at first birth were associated with smoking in patients and controls, explaining a similar percentage of variance in both groups. Attention-deficit hyperactivity disorder (ADHD) PRS was associated with smoking only in schizophrenia. This association remained significant after adjustment by psychiatric cross-disorder PRS. A PRS combining all the traits was more explanative than smoking initiation PRS alone, indicating that genetic susceptibility to the other traits plays an additional role in smoking behaviour. Smoking initiation PRS was also associated with schizophrenia in the whole sample, but the significance was lost after adjustment for smoking status. This same pattern was observed in the analysis of specific SNPs at the CHRNA5-CHRNA3-CHRNB4 cluster associated with both traits. Overall, the results indicate that the same genetic factors are involved in smoking susceptibility in schizophrenia and in general population and are compatible with smoking acting, directly or indirectly, as a risk factor for schizophrenia that contributes to the high prevalence of smoking in these patients. The contrasting results for ADHD PRS may be related to higher ADHD symptomatology in schizophrenic patients.

The Impact of Adolescent Alcohol Exposure on Nicotine Behavioral Sensitization in the Adult Male Neonatal Ventral Hippocampal Lesion Rat

Nicotine and alcohol use is highly prevalent among patients with serious mental illness, including those with schizophrenia (SCZ), and this co-occurrence can lead to a worsening of medical and psychiatric morbidity. While the mechanistic drivers of co-occurring SCZ, nicotine use and alcohol use are unknown, emerging evidence suggests that the use of drugs during adolescence may increase the probability of developing psychiatric disorders. The current study used the neonatal ventral hippocampal lesion (NVHL) rat model of SCZ, which has previously been shown to have enhanced nicotine behavioral sensitization and, following adolescent alcohol, increased alcohol consumption. Given how commonly alcohol is used by adolescents that develop SCZ, we used the NVHL rat to determine how exposure to adolescent alcohol impacts the development of nicotine behavioral sensitization in adulthood. Male Sprague-Dawley rats underwent the NVHL surgery or a sham (control) surgery and subsequently, half of each group was allowed to drink alcohol during adolescence. Nicotine behavioral sensitization was assessed in adulthood with rats receiving subcutaneous injections of nicotine (0.5 mg/kg) each day for 3 weeks followed by a nicotine challenge session 2 weeks later. We demonstrate that all groups of rats became sensitized to nicotine and there were no NVHL-specific increases in nicotine behavioral sensitization. We also found that NVHL rats appeared to develop sensitization to the nicotine paired context and that adolescent alcohol exposure blocked this context sensitization. The current findings suggest that exposure to alcohol during adolescence can influence behaviors that manifest in the adult NVHL rat (i.e., context sensitization). Interestingly, nicotine behavioral sensitization levels were not altered in the NVHL groups regardless of adolescent alcohol exposure in contrast to prior reports.

Drinking and smoking polygenic risk is associated with childhood and early-adulthood psychiatric and behavioral traits independently of substance use and psychiatric genetic risk

Alcohol drinking and tobacco smoking are hazardous behaviors associated with a wide range of adverse health outcomes. In this study, we explored the association of polygenic risk scores (PRS) related to drinks per week, age of smoking initiation, smoking initiation, cigarettes per day, and smoking cessation with 433 psychiatric and behavioral traits in 4498 children and young adults (aged 8-21) of European ancestry from the Philadelphia neurodevelopmental cohort. After applying a false discovery rate multiple testing correction accounting for the number of PRS and traits tested, we identified 36 associations related to psychotic symptoms, emotion and age recognition social competencies, verbal reasoning, anxiety-related traits, parents' education, and substance use. These associations were independent of the genetic correlations among the alcohol-drinking and tobacco-smoking traits and those with cognitive performance, educational attainment, risk-taking behaviors, and psychopathology. The removal of participants endorsing substance use did not affect the associations of each PRS with psychiatric and behavioral traits identified as significant in the discovery analyses. Gene-ontology enrichment analyses identified several neurobiological processes underlying mechanisms of the PRS associations we report. In conclusion, we provide novel insights into the genetic overlap of smoking and drinking behaviors in children and young adults, highlighting their independence from psychopathology and substance use.

Impact of previous tobacco use with or without cannabis on first psychotic experiences in patients with first-episode psychosis

OBJECTIVE

There is high prevalence of cigarette smoking in individuals with first-episode psychosis (FEP) prior to psychosis onset. The purpose of the study was to determine the impact of previous tobacco use with or without cannabis on first psychotic experiences in FEP and the impact of this use on age of onset of symptoms, including prodromes.

METHODS

Retrospective analyses from the naturalistic, longitudinal, multicentre, "Phenotype-Genotype and Environmental Interaction. Application of a Predictive Model in First Psychotic Episodes (PEPs)" Study. The authors analysed sociodemographic/clinical data of 284 FEP patients and 231 matched healthy controls, and evaluated first psychotic experiences of patients using the Symptom Onset in Schizophrenia Inventory.

RESULTS

FEP patients had significantly higher prevalence of tobacco, cannabis, and cocaine use than controls. The FEP group with tobacco use only prior to onset (N = 56) had more sleep disturbances (42.9% vs 18.8%, P = 0.003) and lower prevalence of negative symptoms, specifically social withdrawal (33.9% vs 58%, P = 0.007) than FEP with no substance use (N = 70), as well as lower prevalence of ideas of reference (80.4% vs 92.4%, P = 0.015), perceptual abnormalities (46.4% vs 67.4%, P = 0.006), hallucinations (55.4% vs 71.5%, P = 0.029), and disorganised thinking (41.1% vs 61.1%, P = 0.010) than FEP group with previous tobacco and cannabis use (N = 144). FEP patients with cannabis and tobacco use had lower age at first prodromal or psychotic symptom (mean = 23.73 years [SD = 5.09]) versus those with tobacco use only (mean = 26.21 [SD = 4.80]) (P = 0.011).

CONCLUSIONS

The use of tobacco alone was not related to earlier age of onset of a first psychotic experience, but the clinical profile of FEP patients is different depending on previous tobacco use with or without cannabis.

Association between tobacco use and symptomatology in individuals at ultra-high risk to develop a psychosis: A longitudinal study

BACKGROUND

The high prevalence rates and impact of tobacco smoking in individuals with a psychotic disorder have become an increasing interest. Little is known about tobacco smoking in individuals at ultra-high risk of psychosis (UHR).

METHODS

We studied 345 UHR individuals of the high-risk study of the European network of national schizophrenia networks studying Gene-Environment Interactions (EU-GEI). Smoking status and the number of cigarettes per day were assessed at multiple moments using the CIDI. Symptom severity at each time point was assessed using CAARMS. Linear mixed-effects analyses were conducted to examine the multi-cross-sectional and prospective associations between (change in) smoking behaviour and symptomatology.

FINDINGS

At baseline, 175 individuals (53%) smoked tobacco with an average of 12.4 (SD = 9.0) cigarettes per day. Smokers did not significantly differ in symptom severity from non-smokers on general, positive, negative, emotional, cognitive, behavioural, or motor symptoms across time. However, associations were found between the number of cigarettes and the severity of general psychopathology (estimate 0.349, SE 0.146, p = 0.017). Change in the number of cigarettes had no significant effect on change in general symptom severity (estimate 0.330, SE 0.285, p = 0.248).

INTERPRETATION

Smoking prevalence in UHR individuals is high. Cigarette consumption was associated with higher levels of general symptoms. However, we observed no association between change in number of cigarettes and symptom severity. Given the fact that smoking is associated with poorer health and worse outcomes in people with psychosis, the clinical high-risk phase offers a window of opportunity for prevention and cessation interventions.

Impact of smoking Behavior on cognitive functioning in persons at risk for psychosis and healthy controls: A longitudinal study

Background

The high prevalence of smoking in individuals who are at ultra-high risk (UHR) for psychosis is well known and moderate cognitive deficits have also been found in UHR. However, the association between smoking and cognition in UHR is unknown and longitudinal studies are lacking.

Method

A cohort study with 330 UHR individuals and 66 controls was conducted, as part of the European network of national schizophrenia networks studying gene–environment interactions (EU-GEI). At baseline and after 6, 12, and 24 months, smoking behavior was assessed with the Composite International Diagnostic Interview and cognitive functioning with a comprehensive test battery. Linear mixed-effects analyses were used to examine the multicross-sectional and prospective associations between (change in) smoking behavior and cognitive functioning, accounting for confounding variables.

Results

At baseline, 53% of UHR and 27% of controls smoked tobacco. Smoking UHR and controls did not significantly differ from nonsmoking counterparts on the tested cognitive domains (speed of processing, attention/vigilance, working memory, verbal learning, or reasoning/problem solving) across different assessment times. Neither smoking cessation nor initiation was associated with a significant change in cognitive functioning in UHR.

Conclusions

No associations were found between smoking and cognitive impairment in UHR nor in controls. However, the fact that one in every two UHR individuals report daily use of tobacco is alarming. Our data suggest that UHR have fewer cognitive impairments and higher smoking cessation rates compared to patients with first-episode psychosis found in literature. Implications to promote smoking cessation in the UHR stage need further investigation.

A genetically informed study on the association of cannabis, alcohol, and tobacco smoking with suicide attempt

Use of substances such as cannabis, alcohol, and tobacco, has been associated with increased risk of suicide attempt in several observational studies. However, establishing whether these associations are causal is challenging when using observational designs. To evaluate the potential causal contributions of cannabis use, alcohol use, and tobacco smoking to suicide attempt, we applied two-sample Mendelian randomization, an instrumental variable approach using single-nucleotide polymorphisms (SNPs) as instrumental variables for three exposures: lifetime cannabis use (yes/no; 42 instrument SNPs; GWAS sample size [N] = 162,082), alcohol use (drinks-per-week; 53 instrument SNPs; N = 941,280), and tobacco smoking (initiation, yes/no; 156 instrument SNPs; N = 1,232,091; heaviness; 27 instrument SNPs; N = 337,334). The main outcome was suicide attempt measured from hospital records (N = 50,264). All data come from publicly available summary statistics of genome-wide association studies of participants of European ancestry. We found evidence supporting a possible causal role of cannabis (OR = 1.18; 95% CI = 1.01-1.37, P = 0.032), alcohol (OR = 1.95; 95% CI = 1.15-3.32, P = 0.013), and smoking (initiation, OR = 1.90; 95% CI = 1.54-2.34, P < 0.001; heaviness, OR = 2.13; 95% CI = 1.13-3.99; P = 0.019) on suicide attempt. Using multivariable Mendelian randomization, we found that only cannabis showed a direct pathway to suicide attempt (P = 0.001), suggesting that the effect of alcohol and smoking was mediated by the other substance use phenotypes. No evidence was found for reverse causation, i.e., associations of suicide attempt on cannabis (P = 0.483), alcohol (P = 0.234), smoking initiation (P = 0.144), and heaviness (P = 0.601). In conclusion, evidence from this quasi-experimental study based on genetic data from large-scale GWASs are consistent with a causal role of cannabis, alcohol, and tobacco smoking on suicide attempt.

Smoking and Neuropsychiatric Disease-Associations and Underlying Mechanisms

Despite extensive efforts to combat cigarette smoking/tobacco use, it still remains a leading cause of global morbidity and mortality, killing more than eight million people each year. While tobacco smoking is a major risk factor for non-communicable diseases related to the four main groups—cardiovascular disease, cancer, chronic lung disease, and diabetes—its impact on neuropsychiatric risk is rather elusive. The aim of this review article is to emphasize the importance of smoking as a potential risk factor for neuropsychiatric disease and to identify central pathophysiological mechanisms that may contribute to this relationship. There is strong evidence from epidemiological and experimental studies indicating that smoking may increase the risk of various neuropsychiatric diseases, such as dementia/cognitive decline, schizophrenia/psychosis, depression, anxiety disorder, and suicidal behavior induced by structural and functional alterations of the central nervous system, mainly centered on inflammatory and oxidative stress pathways. From a public health perspective, preventive measures and policies designed to counteract the global epidemic of smoking should necessarily include warnings and actions that address the risk of neuropsychiatric disease.

Environmental Risk Factors for Schizophrenia and Bipolar Disorder and Their Relationship to Genetic Risk: Current Knowledge and Future Directions

Schizophrenia (SZ) and bipolar disorder (BD) are severe psychiatric disorders which result from complex interplay between genetic and environmental factors. It is well-established that they are highly heritable disorders, and considerable progress has been made identifying their shared and distinct genetic risk factors. However, the 15-40% of risk that is derived from environmental sources is less definitively known. Environmental factors that have been repeatedly investigated and often associated with SZ include: obstetric complications, infections, winter or spring birth, migration, urban living, childhood adversity, and cannabis use. There is evidence that childhood adversity and some types of infections are also associated with BD. Evidence for other risk factors in BD is weaker due to fewer studies and often smaller sample sizes. Relatively few environmental exposures have ever been examined for SZ or BD, and additional ones likely remain to be discovered. A complete picture of how genetic and environmental risk factors confer risk for these disorders requires an understanding of how they interact. Early gene-by-environment interaction studies for both SZ and BD often involved candidate genes and were underpowered. Larger samples with genome-wide data and polygenic risk scores now offer enhanced prospects to reveal genetic interactions with environmental exposures that contribute to risk for these disorders. Overall, although some environmental risk factors have been identified for SZ, few have been for BD, and the extent to which these account for the total risk from environmental sources remains unknown. For both disorders, interactions between genetic and environmental risk factors are also not well understood and merit further investigation. Questions remain regarding the mechanisms by which risk factors exert their effects, and the ways in which environmental factors differ by sex. Concurrent investigations of environmental and genetic risk factors in SZ and BD are needed as we work toward a more comprehensive understanding of the ways in which these disorders arise.

Brain gene co-expression networks link complement signaling with convergent synaptic pathology in schizophrenia

The most significant common variant association for schizophrenia (SCZ) reflects increased expression of the complement component 4A (C4A). Yet, it remains unclear how C4A interacts with other SCZ risk genes or whether the complement system more broadly is implicated in SCZ pathogenesis. Here, we integrate several existing, large-scale genetic and transcriptomic datasets to interrogate the functional role of the complement system and C4A in the human brain. Unexpectedly, we find no significant genetic enrichment among known complement system genes for SCZ. Conversely, brain co-expression network analyses using C4A as a seed gene reveal that genes downregulated when C4A expression increases exhibit strong and specific genetic enrichment for SCZ risk. This convergent genomic signal reflects synaptic processes, is sexually dimorphic and most prominent in frontal cortical brain regions, and is accentuated by smoking. Overall, these results indicate that synaptic pathways-rather than the complement system-are the driving force conferring SCZ risk.

Genome-wide analyses of smoking behaviors in schizophrenia: Findings from the Psychiatric Genomics Consortium

While 17% of US adults use tobacco regularly, smoking rates among persons with schizophrenia are upwards of 60%. Research supports a shared etiological basis for smoking and schizophrenia, including findings from genome-wide association studies (GWAS). However, few studies have directly tested whether the same or distinct genetic variants also influence smoking behavior among schizophrenia cases. Using data from the Psychiatric Genomics Consortium (PGC) study of schizophrenia (35476 cases, 46839 controls), we estimated genetic correlations between these traits and tested whether polygenic risk scores (PRS) constructed from the results of smoking behaviors GWAS were associated with schizophrenia risk or smoking behaviors among schizophrenia cases. Results indicated significant genetic correlations of schizophrenia with smoking initiation (rg = 0.159; P = 5.05 × 10-10), cigarettes-smoked-per-day (rg = 0.094; P = 0.006), and age-of-onset of smoking (rg = 0.10; P = 0.009). Comparing smoking behaviors among schizophrenia cases to the general population, we observe positive genetic correlations for smoking initiation (rg = 0.624, P = 0.002) and cigarettes-smoked-per-day (rg = 0.689, P = 0.120). Similarly, TAG-based PRS for smoking initiation and cigarettes-smoked-per-day were significantly associated with smoking initiation (P = 3.49 × 10-5) and cigarettes-smoked-per-day (P = 0.007) among schizophrenia cases. We performed the first GWAS of smoking behavior among schizophrenia cases and identified a novel association with cigarettes-smoked-per-day upstream of the TMEM106B gene on chromosome 7p21.3 (rs148253479, P = 3.18 × 10-8, n = 3520). Results provide evidence of a partially shared genetic basis for schizophrenia and smoking behaviors. Additionally, genetic risk factors for smoking behaviors were largely shared across schizophrenia and non-schizophrenia populations. Future research should address mechanisms underlying these associations to aid both schizophrenia and smoking treatment and prevention efforts.

Colocalization of association signals at nicotinic acetylcholine receptor genes between schizophrenia and smoking traits

BACKGROUND

Epidemiological data suggest that smoking may be a risk factor for schizophrenia (SCZ), but more evidence is needed. Two regions coding nicotinic acetylcholine receptor (nAchR) subunits, atCHRNA2 and the CHRNA5/A3/B4 cluster, were associated with SCZ in genome-wide association studies (GWAS). Additionally, a signal at CHRNA4 is near significance. CHRNA2 was also associated with cannabis use disorder (CUD). These regions were also associated with smoking behaviors. If tobacco is a risk factor, the GWAS signals at smoking behaviors and SCZ have to be due to the same causal variants, i.e. they have to colocalize, although colocalization does not necessarily imply causality. Here, we present colocalization analysis at these loci between SCZ and smoking behaviors.

METHODS

The Bayesian approach implemented in coloc was used to check for posterior probability of colocalization versus independent signals at the three loci with some evidence of association with SCZ and smoking behaviors, using GWAS summary statistics. Colocalization was also assessed for positive control traits and CUD. Three different sensibility analyses were used to confirm the results. A visualization tool, LocusCompare, was used to facilitate interpretation of the coloc results.

RESULTS

Evidence for colocalization of GWAS signals between SCZ and smoking behaviors was found for CHRNA2. Evidence for independent causal variants was found for the other two loci. CUD GWAS signal at CHRNA2 colocalizes with SCZ and smoking behaviors.

CONCLUSIONS

Overall, the results indicate that the association between some nAchR subunit genes and SCZ cannot be solely explained by their effect on smoking behaviors.

Cigarette smoking and schizophrenia: Mendelian randomisation study

BACKGROUND

The link between schizophrenia and cigarette smoking has been well established through observational studies. However, the cause-effect relationship remains unclear.

AIMS

We conducted Mendelian randomisation analyses to assess any causal relationship between genetic variants related to four smoking-related traits and the risk of schizophrenia.

METHOD

We performed a two-sample Mendelian randomisation using summary statistics from genome-wide association studies (GWAS) of smoking-related traits and schizophrenia (7711 cases, 18 327 controls) in East Asian populations. Single nucleotide polymorphisms (SNPs) correlated with smoking behaviours (smoking initiation, smoking cessation, age at smoking initiation and quantity of smoking) were investigated in relation to schizophrenia using the inverse-variance weighted (IVW) method. Further sensitivity analyses, including Mendelian randomisation-Egger (MR-Egger), weighted median estimates and leave-one-out analysis, were used to test the consistency of the results.

RESULTS

The associated SNPs for the four smoking behaviours were not significantly associated with schizophrenia status. Pleiotropy did not inappropriately affect the results.

CONCLUSIONS

Cigarette smoking is a complex behaviour in people with schizophrenia. Understanding factors underlying the observed association remains important; however, our findings do not support a causal role of smoking in influencing risk of schizophrenia.

Evidence for a Causal Relationship Between Academic Achievement and Cigarette Smoking

INTRODUCTION

Academic achievement (AA) is associated with smoking rates. Can we determine the degree to which this relationship is likely a causal one?

METHODS

We predict smoking in male conscripts (mean age 18.2) assessed from 1984 to 1991 (N = 233 248) and pregnant females (mean age 27.7) receiving prenatal care 1972-1990 (N = 494 995) from AA assessed in all students at 16. Instrumental variable (IV) analyses used the instrument month-of-birth as in each school year, older children have high AA. Co-relative analyses used AA-smoking associations in the population, cousins and siblings to predict the AA-smoking relationship in MZ twins, thereby controlling for familial confounding.

RESULTS

In males, higher AA was associated with a substantial decrease in risk for smoking (odds ratio [OR] [95% confidence intervals [CIs]] per standard deviation [SD] = 0.41 [0.40-0.41]) while the parallel figures obtain from our IV and co-relative analyses were 0.47 (0.39-0.57) and 0.51 (0.43-0.60), respectively. In females, these figures for pre-pregnancy smoking were, respectively, 0.39 (0.39-0.39), 0.50 (0.46-0.54) and 0.54 (0.51-0.58). Results for heavy versus light smoking suggested a causal effect but were inconsistent across methods. However, among females smoking prior to pregnancy, AA predicted a reduced risk for continued smoking with ORs for uncontrolled, IV, and co-relative analyses equaling, respectively, were 0.54 (0.53-0.55) 0.68 (0.56-0.82) and 0.78 (0.66-0.91), respectively.

CONCLUSIONS

Two different methods produced consistent evidence that higher AA has a causal effect on reducing smoking rates and increasing cessation rates in smoking pregnant females. Improving AA may result in meaningful gains in population health through reduced smoking.

IMPLICATIONS

This study provides consistent evidence across two different methods that high AA is causally related to reduced rates of smoking and increasing rates of smoking cessation among pregnant women. Our results suggest that interventions that improve educational achievement in adolescence would reduce tobacco consumption, thereby improving public health.

Cigarette Smoking and Schizophrenia: Etiology, Clinical, Pharmacological, and Treatment Implications

Recent data suggests that the prevalence of smoking in schizophrenia remains high. While reports suggest that smoking increases the risk of developing schizophrenia, the potential causative role of smoking in this relationship needs further investigation. Smokers with schizophrenia are more likely to have more intense positive symptoms and lower cognitive function, but diminished intensity of extrapyramidal side effects than nonsmoking patients with schizophrenia. They were also more likely to exhibit aggressive behaviour compared to nonsmokers, which could suggest higher levels of baseline aggression. The significant cost associated with regular tobacco expenditure can detract from investment in key domains. Large-scale trials have shown that pharmacotherapy for smoking cessation is effective and does not worsen the risk of developing neuropsychiatric symptoms compared to placebo. Electronic cigarette use among schizophrenia patients is high, and there is emerging evidence supportive of its efficacy. Future improvements include large-scale trials assessing the utility, efficacy, and safety of electronic cigarettes in schizophrenia patients.

Polygenic risk scores for late smoking initiation associated with the risk of schizophrenia

Patients with schizophrenia display characteristic smoking-related behaviors and genetic correlations between smoking behaviors and schizophrenia have been identified in European individuals. However, the genetic etiology of the association remains to be clarified. The present study investigated transethnic genetic overlaps between European-based smoking behaviors and the risk of Japanese schizophrenia by conducting polygenic risk score (PRS) analyses. Large-scale European genome-wide association study (GWAS) datasets (n = 24,114-74,035) related to four smoking-related intermediate phenotypes [(i) smoking initiation, (ii) age at smoking initiation, (iii) smoking quantity, and (iv) smoking cessation] were utilized as discovery samples. PRSs derived from these discovery GWASs were calculated for 332 Japanese subjects [schizophrenia patients, their unaffected first-degree relatives (FRs), and healthy controls (HCs)] as a target sample. Based on GWASs of European smoking phenotypes, we investigated the effects of PRSs on smoking phenotypes and the risk of schizophrenia in the Japanese population. Of the four smoking-related behaviors, the PRSs for age at smoking initiation in Europeans significantly predicted the age at smoking initiation (R² = 0.049, p = 0.026) and the PRSs for smoking cessation significantly predicted the smoking cessation (R² = 0.092, p = 0.027) in Japanese ever-smokers. Furthermore, the PRSs related to age at smoking initiation in Europeans were higher in Japanese schizophrenia patients than in the HCs and those of the FRs were intermediate between those of patients with schizophrenia and those of the HCs (R² = 0.015, p = 0.015). In our target subjects, patients with schizophrenia had a higher mean age at smoking initiation (p = 0.018) and rate of daily smoking initiation after age 20 years (p = 0.023) compared with the HCs. A total of 60.6% of the patients started to smoke before the onset of schizophrenia. These findings suggest that genetic factors affecting late smoking initiation are associated with the risk of schizophrenia.

Evidence for causal effects of lifetime smoking on risk for depression and schizophrenia: a Mendelian randomisation study

BACKGROUND

Smoking prevalence is higher amongst individuals with schizophrenia and depression compared with the general population. Mendelian randomisation (MR) can examine whether this association is causal using genetic variants identified in genome-wide association studies (GWAS).

METHODS

We conducted two-sample MR to explore the bi-directional effects of smoking on schizophrenia and depression. For smoking behaviour, we used (1) smoking initiation GWAS from the GSCAN consortium and (2) we conducted our own GWAS of lifetime smoking behaviour (which captures smoking duration, heaviness and cessation) in a sample of 462690 individuals from the UK Biobank. We validated this instrument using positive control outcomes (e.g. lung cancer). For schizophrenia and depression we used GWAS from the PGC consortium.

RESULTS

There was strong evidence to suggest smoking is a risk factor for both schizophrenia (odds ratio (OR) 2.27, 95% confidence interval (CI) 1.67-3.08, p < 0.001) and depression (OR 1.99, 95% CI 1.71-2.32, p < 0.001). Results were consistent across both lifetime smoking and smoking initiation. We found some evidence that genetic liability to depression increases smoking (β = 0.091, 95% CI 0.027-0.155, p = 0.005) but evidence was mixed for schizophrenia (β = 0.022, 95% CI 0.005-0.038, p = 0.009) with very weak evidence for an effect on smoking initiation.

CONCLUSIONS

These findings suggest that the association between smoking, schizophrenia and depression is due, at least in part, to a causal effect of smoking, providing further evidence for the detrimental consequences of smoking on mental health.

The effects of polygenic risk for psychiatric disorders and smoking behaviour on psychotic experiences in UK Biobank

While psychotic experiences are core symptoms of mental health disorders like schizophrenia, they are also reported by 5-10% of the population. Both smoking behaviour and genetic risk for psychiatric disorders have been associated with psychotic experiences, but the interplay between these factors remains poorly understood. We tested whether smoking status, maternal smoking around birth, and number of packs smoked/year were associated with lifetime occurrence of three psychotic experiences phenotypes: delusions (n = 2067), hallucinations (n = 6689), and any psychotic experience (delusions or hallucinations; n = 7803) in 157,366 UK Biobank participants. We next calculated polygenic risk scores for schizophrenia (PRSSCZ), bipolar disorder (PRSBP), major depression (PRSDEP) and attention deficit hyperactivity disorder (PRSADHD) in 144,818 UK Biobank participants of European ancestry to assess whether association between smoking and psychotic experiences was attenuated after adjustment of diagnosis of psychiatric disorders and the PRSs. Finally, we investigated whether smoking exacerbates the effects of genetic predisposition on the psychotic phenotypes in gene-environment interaction models. Smoking status, maternal smoking, and number of packs smoked/year were associated with psychotic experiences (p < 1.77 × 10-5). Except for packs smoked/year, effects were attenuated but remained significant after adjustment for diagnosis of psychiatric disorders and PRSs (p < 1.99 × 10-3). Gene-environment interaction models showed the effects of PRSDEP and PRSADHD (but not PRSSCZ or PRSBP) on delusions (but not hallucinations) were significantly greater in current smokers compared to never smokers (p < 0.002). There were no significant gene-environment interactions for maternal smoking nor for number of packs smoked/year. Our results suggest that both genetic risk of psychiatric disorders and smoking status may have independent and synergistic effects on specific types of psychotic experiences.

Schizophrenia and Epigenetic Aging Biomarkers: Increased Mortality, Reduced Cancer Risk, and Unique Clozapine Effects

BACKGROUND

Schizophrenia (SZ) is associated with increased all-cause mortality, smoking, and age-associated proteins, yet multiple previous studies found no association between SZ and biological age using Horvath's epigenetic clock, a well-established aging biomarker based on DNA methylation. However, numerous epigenetic clocks that may capture distinct aspects of aging have been developed. This study tested the hypothesis that altered aging in SZ manifests in these other clocks.

METHODS

We performed a comprehensive analysis of 14 epigenetic clocks categorized according to what they were trained to predict: chronological age, mortality, mitotic divisions, or telomere length. To understand the etiology of biological age differences, we also examined DNA methylation predictors of smoking, alcohol, body mass index, serum proteins, and cell proportions. We independently analyzed 3 publicly available multiethnic DNA methylation data sets from whole blood, a total of 567 SZ cases and 594 nonpsychiatric controls.

RESULTS

All data sets showed accelerations in SZ for the 3 mortality clocks up to 5 years, driven by smoking and elevated levels of 6 age-associated proteins. The 2 mitotic clocks were decelerated in SZ related to antitumor natural killer and CD8T cells, which may help explain conflicting reports about low cancer rates in epidemiological studies of SZ. One cohort with available medication data showed that clozapine is associated with male-specific decelerations up to 7 years in multiple chronological age clocks.

CONCLUSIONS

Our study demonstrates the utility of studying the various epigenetic clocks in tandem and highlights potential mechanisms by which mental illness influences long-term outcomes, including cancer and early mortality.

Editorial: Brain Mediators of the Cannabis-Prodromal Psychosis Connection

The article by Yu and Jia et al.¹ in this issue of the Journal investigates the role of a subregion of the parahippocampal gyrus called the right uncus ("hook") as a possible mediator of the known increase of psychotic-like experiences (PLEs) due to the consumption of cannabinoids (ie, cannabis).² The authors chose a pattern of plausible inference worthy of pursuit. Cannabis continues to be one of the most widely used drugs globally, only behind alcohol, caffeine, and tobacco; 188 million people used cannabis worldwide in 2017.³ In January 2019, the WHO's Expert Committee on Drug Dependence (ECDD)⁴ recommended that cannabis be no longer classified as a Schedule IV drug (its medical potential is now deemed to outweigh its abuse potential). It should be noted that cannabidiol (CBD) is a non-psychoactive component of cannabis that has medicial uses in reducing pain and inflammation, controlling epileptic seizures, and possibly even treating mental illness and addiction.⁵ As more world governments legalize cannabis for recreational use, and owing to the widening availability of higher tetrahydrocannabinol content variants of cannabis, the number of cannabis users is increasing rapidly, which in turn increases the number of people having PLEs worldwide. Schizophrenia is one of the top 15 leading causes of disability worldwide.⁶ The estimated prevalence of schizophrenia and related psychotic disorders in the United States in 2005 ranged from 0.25% to 0.64%⁷; a meta-analysis a decade later found the lifetime prevalence worldwide to be 0.48% with interquartile range 0.34% to 0.85%.⁸ The high variability of sampling domains, diagnostic criteria, data availability and analytic methods employed preclude reliable estimates of incidence and prevalence increases of schizophrenia at present.

Identification of 34 genes conferring genetic and pharmacological risk for the comorbidity of schizophrenia and smoking behaviors

The prevalence of smoking is significantly higher in persons with schizophrenia (SCZ) than in the general population. However, the biological mechanisms of the comorbidity of smoking and SCZ are largely unknown. This study aimed to reveal shared biological pathways for the two diseases by analyzing data from two genome-wide association studies with a total sample size of 153,898. With pathway-based analysis, we first discovered 18 significantly enriched pathways shared by SCZ and smoking, which were classified into five groups: postsynaptic density, cadherin binding, dendritic spine, long-term depression, and axon guidance. Then, by using an integrative analysis of genetic, epigenetic, and expression data, we found not only 34 critical genes (e.g., PRKCZ, ARHGEF3, and CDKN1A) but also various risk-associated SNPs in these genes, which convey susceptibility to the comorbidity of the two disorders. Finally, using both in vivo and in vitro data, we demonstrated that the expression profiles of the 34 genes were significantly altered by multiple psychotropic drugs. Together, this multi-omics study not only reveals target genes for new drugs to treat SCZ but also reveals new insights into the shared genetic vulnerabilities of SCZ and smoking behaviors.

Nicotine consumption during the prodromal phase of schizophrenia - a review of the literature

Recent research has fueled a debate concerning the role of nicotine in the emergence of schizophrenia. The three main hypotheses are: (a) the self-medication effect, (b) the causal relationship hypothesis, or (c) the shared diathesis hypothesis. To explore this role, the study of nicotine consumption during the initial prodromal phase of schizophrenia offers important opportunities. In the present work, 10 relevant studies are reviewed, out of 727 retrieved citations, in order to address questions regarding the prevalence of smoking in the prodromal period, the time of smoking initiation, existing patterns of tobacco use in relation with the escalation of prodromal symptoms into first psychotic episode, and potential differences in symptomatology between smokers and nonsmokers. Even though there was considerable heterogeneity among studies, relevant findings are discussed. Prevalence of nicotine use during the prodromal period was reported to be 16.6-46%. Tobacco use was found to be taken up most often before or during the prodromal period of schizophrenia. Even though a protective role of smoking has been reported by one study, other studies report an increased risk for psychosis, with hazard ratios 2.77 (95% CI: 2.34-3.43) and 2.21 (95% CI: 1.11-4.42) for female and male heavy smokers (11-20 and >20 cigarettes/day), respectively. In a different study, the risk of onset was associated with the progressive use of cannabis and tobacco prior to onset, particularly with rapid escalation to the highest levels of use. Also, nicotine use in ultra high risk (UHR) for developing psychosis subjects is associated with elevated cognitive performance, namely better processing speed, visual learning, and spatial working memory. As a conclusion, it appears that evidence accumulates supporting a possible etiologic role of smoking, in the emergence of schizophrenia along with diverse effects on patients' symptomatology, already demonstrable at the prodromal phase. Future research employing better-defined criteria should further explore the patterns of use and effects of nicotine during the schizophrenia prodrome.

Tobacco use and psychosis risk in persons at clinical high risk

AIM

To evaluate the role of tobacco use in the development of psychosis in individuals at clinical high risk.

METHOD

The North American Prodrome Longitudinal Study is a 2-year multi-site prospective case control study of persons at clinical high risk that aims to better understand predictors and mechanisms for the development of psychosis. The cohort consisted of 764 clinical high risk and 279 healthy comparison subjects. Clinical assessments included tobacco and substance use and several risk factors associated with smoking in general population studies.

RESULTS

Clinical high risk subjects were more likely to smoke cigarettes than unaffected subjects (light smoking odds ratio [OR] = 3.0, 95% confidence interval [CI] = 1.9-5; heavy smoking OR = 4.8, 95% CI = 1.7-13.7). In both groups, smoking was associated with mood, substance use, stress and perceived discrimination and in clinical high risk subjects with childhood emotional neglect and adaption to school. Clinical high risk subjects reported higher rates of several factors previously associated with smoking, including substance use, anxiety, trauma and perceived discrimination. After controlling for these potential factors, the relationship between clinical high risk state and smoking was no longer significant (light smoking OR = 0.9, 95% CI = 0.4-2.2; heavy smoking OR = 0.3, 95% CI = 0.05-2.3). Moreover, baseline smoking status (hazard ratio [HR] = 1.16, 95% CI = 0.82-1.65) and categorization as ever smoked (HR = 1.3, 95% CI = 0.8-2.1) did not predict time to conversion.

CONCLUSION

Persons at high risk for psychosis are more likely to smoke and have more factors associated with smoking than controls. Smoking status in clinical high risk subjects does not predict conversion. These findings do not support a causal relationship between smoking and psychosis.

Individual-level and area-level socioeconomic status (SES) and schizophrenia: cross-sectional analyses using the evidence from 1.9 million Chinese adults

OBJECTIVES

Health disparities in schizophrenia are well established. However, it is less understood whether area-level socioeconomic status (SES) is differentially associated with schizophrenia depending on individual-level SES. Therefore, using a nationally large representative data, this study investigated the association between individual-level SES, area-level SES and their interaction with schizophrenia in Chinese adults from a multilevel perspective.

SETTING

Household interviews in 734 counties (districts), 2980 towns (streets) and 5964 communities (villages) from 31 provinces, People's Republic of China, as part of the cross-sectional survey of Second China National Sample Survey on Disability.

PARTICIPANTS

1 909 205 men and women aged 18 years old and above.

PRIMARY AND SECONDARY OUTCOME MEASURES

A screen followed by clinical diagnosis was used to identify schizophrenia, and schizophrenia was ascertained according to the International Statistical Classification of Diseases, 10th Revision (code F20).

RESULTS

1-SD increase in individual SES was associated with decreased risk of schizophrenia (OR=0.45, 95% CI 0.43 to 0.46). 1-SD increase in area-level SES was associated with increased risk of schizophrenia (OR=1.30, 95% CI 1.24 to 1.37). The interaction of individual SES and area-level SES was statistically significant (OR=1.05, 95% CI 1.02 to 1.08); as the level of area SES increased, schizophrenia risk of lower SES people grew faster than the risk of higher SES people.

CONCLUSIONS

Area-level SES is particularly important to mental health of low SES individuals, with low SES people in high SES counties having the highest risk of schizophrenia than other groups. Action to reduce SES disparities in schizophrenia will require attention to the area-level context of low SES adults.

The relationship between nicotine and psychosis

Cigarette smoking is strongly associated with psychotic disorders such as schizophrenia. For several decades it was assumed that the relationship could be explained by reverse causation; that smoking was secondary to the illness itself, either through self-medication or a process of institutionalization, or was entirely explained by confounding by cannabis use or social factors. However, studies have exposed that such hypotheses cannot fully explain the association, and more recently a bidirectional relationship has been proposed wherein cigarette smoking may be causally related to risk of psychosis, possibly via a shared genetic liability to smoking and psychosis. We review the evidence for these candidate explanations, using findings from the latest epidemiological, neuroimaging, genetic and preclinical work.

Tobacco smoking and schizophrenia: re-examining the evidence

Tobacco smoking among people with mental illnesses can be explained by biological, psychological and social factors. The prevalence of smoking in people diagnosed with schizophrenia is higher than in people with other mental disorders and in the general population. This article explores three current hypotheses that explain this higher prevalence of smoking in schizophrenia. The first, the self-medication hypothesis, is increasingly countered by a growing body of evidence indicating that smokers experience more severe symptoms of schizophrenia. Numerous researchers have already identified smoking as a possible risk factor for the development of schizophrenia, which is the second hypothesis. The third hypothesis (shared genetic vulnerability) identifies certain genes that confer vulnerability for both schizophrenia and nicotine dependence. Understanding the reasons behind the higher prevalence of smoking among people with schizophrenia is vital in planning effective primary, secondary and tertiary smoking prevention for these individuals.

LEARNING OBJECTIVES

At the end of this article, readers will be able to: •

Genome-Wide Variants Shared Between Smoking Quantity and Schizophrenia on 15q25 Are Associated With CHRNA5 Expression in the Brain

Cigarette smokers with schizophrenia consume more cigarettes than smokers in the general population. Schizophrenia and smoking quantity may have shared genetic liability. Genome-wide association studies (GWASs) of schizophrenia and smoking quantity have highlighted a biological pleiotropy in which a robust 15q25 locus affects both traits. To identify the genetic variants shared between these traits on 15q25, we used summary statistics from large-scale GWAS meta-analyses of schizophrenia in the Psychiatric Genomics Consortium 2 and smoking quantity assessed by cigarettes smoked per day in the Tobacco and Genetics Consortium. To evaluate the regulatory potential of the shared genetic variants, expression quantitative trait loci analysis in 10 postmortem brain regions was performed using the BRAINEAC dataset in 134 neuropathologically normal individuals. Twenty-two genetic variants on 15q25 were associated with both smoking quantity and schizophrenia at the genome-wide significance level (P < 5.00 × 10-8). Major alleles of all variants were associated with higher smoking quantity and risk of schizophrenia. These genetic variants were associated with PSMA4, CHRNA3, and CHRNB4 expression in specific brain regions (lowest P = 4.81 × 10-4) and with CHRNA5 expression in multiple brain regions (lowest P = 8.70 × 10-6). Risk-associated major alleles of these variants were commonly associated with higher expression in several brain regions, excluding the medulla, at the transcript level. In addition, the risk-associated major allele at rs637137 was associated with higher CHRNA5 expression at the specific exon level in multiple brain regions (lowest P = 2.37 × 10-5). Our findings suggest that genome-wide variants shared between smoking quantity and schizophrenia contribute to a common pathophysiology underlying these traits involving altered CHRNA5 expression in the brain.

Tobacco smoking is associated with antipsychotic medication, physical aggressiveness, and alcohol use disorder in schizophrenia: results from the FACE-SZ national cohort

Tobacco smoking is common in schizophrenia and is one of the main causes of premature mortality in this disorder. Little is known about clinical correlates and treatments associated with tobacco smoking in patients with schizophrenia. Still, a better characterization of these patients is necessary, in a personalized care approach. Aggressiveness and childhood trauma have been associated with tobacco smoking in general population, but this association has never been explored in schizophrenia. Our study examines the clinical and therapeutic characteristics of tobacco smoking in schizophrenia. 474 stabilized patients (mean age = 32.2; 75.7% male gender; smokers n = 207, 54.6%) were consecutively included in the network of the FondaMental Expert centers for Schizophrenia and assessed with valid scales. Current tobacco status was self-declared. Aggressiveness was self-reported with Buss-Perry Aggressiveness Questionnaire and Childhood Trauma with Childhood Trauma Questionnaire. Ongoing treatment was reported. In univariate analysis, tobacco smoking was associated with lower education level (p < 0.01), positive syndrome (p < 0.01), higher physical aggressiveness (p < 0.001), alcohol dependence (p < 0.001), and First Generation Antipsychotics (FGAs) use (p = 0.018). In a multivariate model, tobacco smoking remained associated with physical aggressiveness (p < 0.05), current alcohol dependence (p < 0.01) and FGA use (p < 0.05). No association was observed with childhood trauma history, mood disorder, suicidal behavior, psychotic symptom, global functioning or medication adherence. Patients with tobacco use present clinical and therapeutic specificities, questioning the neurobiological links between tobacco and schizophrenia. They could represent a specific phenotype, with specific clinical and therapeutic specificities that may involve interactions between cholinergic-nicotinic system and dopaminergic system. Further longitudinal studies are needed to confirm the potential efficacy of second generation antipsychotics (SGAs) on tobacco use in schizophrenia and to develop effective strategies for tobacco cessation in this population.