Association of Combined Patterns of Tobacco and Cannabis Use in Adolescence With Psychotic Experiences

The association between childhood trauma and tobacco smoking in patients with psychosis, unaffected siblings, and healthy controls

In patients with psychosis, rates of tobacco smoking and childhood trauma are significantly higher compared to the general population. Childhood trauma has been proposed as a risk factor for tobacco smoking. However, little is known about the relationship between childhood trauma and smoking in psychosis. In a subsample of the Genetic Risk and Outcome of Psychosis study (760 patients with psychosis, 991 unaffected siblings, and 491 healthy controls), tobacco smoking was assessed using the Composite International Diagnostic Interview and childhood trauma was measured with the Childhood Trauma Questionnaire. Logistic regression models were used to assess associations between trauma and smoking, while correcting for confounders. Positive associations were found between total trauma, abuse, and neglect, and an increased risk for smoking in patients, while correcting for age and gender (ORtrauma 1.77, 95% CI 1.30-2.42, p < 0.001; ORabuse 1.69, 95% CI 1.23-2.31, p = 0.001; ORneglect 1.48, 95% CI 1.08-2.02, p = 0.014). In controls, total trauma and abuse were positively associated with smoking, while correcting for age and gender (ORtrauma 2.40, 95% CI 1.49-3.88, p < 0.001; ORabuse 2.02, 96% CI 1.23-3.32, p = 0.006). All associations lost their significance after controlling for additional covariates and multiple testing. Findings suggest that the association between childhood trauma and tobacco smoking can be mainly explained by confounders (gender, cannabis use, and education) in patients with psychosis. These identified aspects should be acknowledged in tobacco cessation programs.

Heavy metal concentrations and clinical symptoms in patients diagnosed with schizophrenia related to cigarette smoking

In our study, blood concentrations of lead (Pb), arsenic (As), and cadmium (Cd) and urine concentrations of thallium (Tl) were measured together with related symptoms of heavy metal poisoning in cigarette smoking volunteers diagnosed with schizophrenia, in cigarette smokers not diagnosed with schizophrenia, and in the control group of non-smokers and not diagnosed with schizophrenia volunteers. Our study was performed on 171 volunteers divided into the following subgroups: patients diagnosed with schizophrenia with at least 1 year of continuous cigarette smoking experience (56 participants), cigarette smokers not diagnosed with schizophrenia with at least one year of continuous smoking experience (58), and control group (not diagnosed with schizophrenia and non-smoking volunteers) (57). Smoking durations of cigarette smokers diagnosed with schizophrenia and cigarette smokers not diagnosed with schizophrenia are not similar (p = 0.431). Blood Pb, As, and Cd concentrations and urine Tl concentrations were the highest in the subgroup of cigarette smokers not diagnosed with schizophrenia, followed by the subgroup of cigarette smokers diagnosed with schizophrenia, and the control group. Only blood Pb concentrations were significantly higher (probability value p < 0.05) in the group of cigarette smokers not diagnosed with schizophrenia (5.16 μg/dL), comparing to the group of cigarette smokers diagnosed with schizophrenia (3.83 μg/dL) and to the control group (3.43 μg/dL). Blood Cd and As concentrations and urine Tl concentrations were significantly higher (p < 0.05) in cigarette smokers not diagnosed with schizophrenia than in the control group. The results revealed a statistically significant positive correlation (p < 0.001) in the cigarette smokers in the schizophrenia diagnosed group between blood Pb, blood As, and urine Tl concentrations and the duration of cigarette smoking.

Sexual Minority Status and Psychotic Experiences Among Young Adult College Students in the United States

2020-2021 Healthy Minds Study, and used multivariable logistic regression to examine the associations between sexual minority status and psychotic experiences, adjusting for age, gender, and race/ethnicity. We then tested whether psychosocial factors accounted for the association. Sexual minority status was associated with 1.87 times greater odds of having psychotic experiences over the past 12 months (aOR: 1.87; 95% CI: 1.77-1.99; N = 110,551). Several factors mediated the association between sexual orientation and psychotic experiences such as loneliness (26.93%), anxiety (30.90%), depression (33.18%), and marijuana use (13.95%); all factors together accounted for 59.01% of the association between sexual minority status and psychotic experiences. Food insecurity, recent abuse, and discrimination did not significantly mediate the association. Findings should raise clinical awareness that psychotic experiences are more common among sexual minorities than among heterosexuals, which is largely explained by mental health factors, calling for targeted outreach and intervention.

Relationship between mood disorders and substance involvement and the shared genetic liabilities: A population-based study in Taiwan

BACKGROUND

This study explored the phenotypic association of mood disorders, including major depressive disorder (MDD) and bipolar disorder (BPD), with a range of substance involvement, including lifetime experience and age at initiation of tobacco, alcohol, and betel nut use. Additionally, we elucidated polygenic risk score (PRS) association.

METHODS

In total, 132,615 community participants were recruited from the Taiwan Biobank. Genome-wide genotyping data were available for 106,806 unrelated individuals, and the PRS for MDD and BPD was calculated. The significance of mood disorders and PRSs associated with substance involvement were evaluated using a linear/logistic regression model with adjustment for potential confounders. Sex differences were assessed.

RESULTS

MDD and BPD were associated with regular alcohol consumption, drinking cessation, tobacco smoking, smoking cessation, betel nut chewing, and earlier onset of drinking. BPD was associated with an earlier onset of smoking. MDD PRS was associated with regular alcohol use (odds ratio [OR] per standard deviation increase in PRS = 1.03, p = 0.018), alcohol cessation (OR = 1.05, p = 0.03), regular tobacco use (OR = 1.08, p < 0.0001), and betel nut chewing (OR = 1.06, p < 0.0001), whereas BPD PRS was not associated with substance use. Phenotypic association strengths between MDD/BPD and regular drinking/smoking and the polygenic association between MDD PRS and regular smoking were larger in females than in males.

LIMITATIONS

Retrospective self-reported MDD/BPD diagnoses and substance involvement.

CONCLUSIONS

Mood disorders were associated with a range of substance involvement. Shared genetic architecture contributed to the co-occurrence of MDD and substance involvement. These findings may help design prevention and cessation strategies for substance use.

Unhealthy behaviors associated with mental health disorders: a systematic comparative review of diet quality, sedentary behavior, and cannabis and tobacco use

Background

There are well-established literatures documenting the associations between mental disorders and unhealthy behaviors such as poor diet quality, sedentary behavior, and cannabis and tobacco use. Few studies have attempted to understand the respective findings in light of each other, however.

Objective

The purpose of this review was to assemble comparable data for each behavior-disorder association and assess the associations in terms of their overall strength. The review aimed to include a representative, but not exhaustive, range of studies that would allow for explorative comparisons.

Methods

Eligible studies were identified via Pubmed searches and citation searching, restricted to publications no older than 2015 written in English. To obtain comparable data, only studies that reported findings as odds ratios were included, and risk of bias related to study samples, behavioral measurement disparities, and control variables was assessed via sensitivity analyses. Findings for each disorder were compared on the basis of different measures of central tendency.

Results

From 3,682 records, 294 studies were included. The review found evidence of associations between each of the four unhealthy behaviors and psychosis, depression, anxiety, bipolar disorder, attention-deficit/hyperactivity disorder (ADHD), and post-traumatic stress disorder (PTSD), while personality disorder was only investigated in relation to cannabis and tobacco use. In overall comparison, the associations were generally of similar strength, and only the association between cannabis use and personality disorder was exceptional in terms of being significantly stronger than its counterparts across disorders and across behaviors. Analyses of bias risk identified some influence from behavioral measurement disparities and lack of adequate statistical control, but findings were generally robust across a range of sensitivity analyses.

Conclusion

This explorative and comparative review found that poor diet quality, sedentary behavior, and cannabis and tobacco use are about equally strongly associated with a range of different mental disorders. Given the general nature of these associations, we should probably understand them to reflect a general and shared etiology. However, the findings in this review should be regarded as tentative until confirmed by more comprehensive investigations.

Tobacco use in first-episode psychosis, a multinational EU-GEI study

BACKGROUND

Tobacco is a highly prevalent substance of abuse in patients with psychosis. Previous studies have reported an association between tobacco use and schizophrenia. The aim of this study was to analyze the relationship between tobacco use and first-episode psychosis (FEP), age at onset of psychosis, and specific diagnosis of psychosis.

METHODS

The sample consisted of 1105 FEP patients and 1355 controls from the European Network of National Schizophrenia Networks Studying Gene-Environment Interactions (EU-GEI) study. We assessed substance use with the Tobacco and Alcohol Questionnaire and performed a series of regression analyses using case-control status, age of onset of psychosis, and diagnosis as outcomes and tobacco use and frequency of tobacco use as predictors. Analyses were adjusted for sociodemographic characteristics, alcohol, and cannabis use.

RESULTS

After controlling for cannabis use, FEP patients were 2.6 times more likely to use tobacco [p ⩽ 0.001; adjusted odds ratio (AOR) 2.6; 95% confidence interval (CI) [2.1-3.2]] and 1.7 times more likely to smoke 20 or more cigarettes a day (p = 0.003; AOR 1.7; 95% CI [1.2-2.4]) than controls. Tobacco use was associated with an earlier age at psychosis onset (β = -2.3; p ⩽ 0.001; 95% CI [-3.7 to -0.9]) and was 1.3 times more frequent in FEP patients with a diagnosis of schizophrenia than in other diagnoses of psychosis (AOR 1.3; 95% CI [1.0-1.8]); however, these results were no longer significant after controlling for cannabis use.

CONCLUSIONS

Tobacco and heavy-tobacco use are associated with increased odds of FEP. These findings further support the relevance of tobacco prevention in young populations.

Independent contribution of polygenic risk for schizophrenia and cannabis use in predicting psychotic-like experiences in young adulthood: testing gene × environment moderation and mediation

BACKGROUND

It has not yet been determined if the commonly reported cannabis-psychosis association is limited to individuals with pre-existing genetic risk for psychotic disorders.

METHODS

We examined whether the relationship between polygenic risk score for schizophrenia (PRS-Sz) and psychotic-like experiences (PLEs), as measured by the Community Assessment of Psychic Experiences-42 (CAPE-42) questionnaire, is mediated or moderated by lifetime cannabis use at 16 years of age in 1740 of the individuals of the European IMAGEN cohort. Secondary analysis examined the relationships between lifetime cannabis use, PRS-Sz and the various sub-scales of the CAPE-42. Sensitivity analyses including covariates, including a PRS for cannabis use, were conducted and results were replicated using data from 1223 individuals in the Dutch Utrecht cannabis cohort.

RESULTS

PRS-Sz significantly predicted cannabis use (p = 0.027) and PLE (p = 0.004) in the IMAGEN cohort. In the full model, considering PRS-Sz and covariates, cannabis use was also significantly associated with PLE in IMAGEN (p = 0.007). Results remained consistent in the Utrecht cohort and through sensitivity analyses. Nevertheless, there was no evidence of a mediation or moderation effects.

CONCLUSIONS

These results suggest that cannabis use remains a risk factor for PLEs, over and above genetic vulnerability for schizophrenia. This research does not support the notion that the cannabis-psychosis link is limited to individuals who are genetically predisposed to psychosis and suggests a need for research focusing on cannabis-related processes in psychosis that cannot be explained by genetic vulnerability.

A multicomponent psychosocial intervention to reduce substance use by adolescents involved in the criminal justice system: the RISKIT-CJS RCT

Background

Substance use and offending are related in the context of other disinhibitory behaviours. Adolescents involved in the criminal justice system constitute a particularly vulnerable group, with a propensity to engage in risky behaviour that has long-term impact on their future health and well-being. Previous research of the RISKIT programme provided evidence of a potential effect in reducing substance use and risky behaviour in adolescents.

Objectives

To evaluate the clinical effectiveness and cost-effectiveness of a multicomponent psychosocial intervention compared with treatment as usual in reducing substance use for substance-using adolescents involved in the criminal justice system.

Design

A mixed-methods, prospective, pragmatic, two-arm, randomised controlled trial with follow-up at 6 and 12 months post randomisation.

Setting

The study was conducted across youth offending teams, pupil referral units and substance misuse teams across four areas of England (i.e. South East, London, North West, North East).

Participants

Adolescents aged between 13 and 17 years (inclusive), recruited between September 2017 and June 2020.

Interventions

Participants were randomised to treatment as usual or to treatment as usual in addition to the RISKIT-Criminal Justice System (RISKIT-CJS) programme. The RISKIT-CJS programme was a multicomponent intervention and consisted of two individual motivational interviews with a trained youth worker (lasting 45 minutes each) and two group sessions delivered over half a day on consecutive weeks.

Main outcome measures

At 12 months, we assessed per cent days abstinent from substance use over the previous 28 days. Secondary outcome measures included well-being, motivational state, situational confidence, quality of life, resource use and fidelity of interventions delivered.

Results

A total of 693 adolescents were assessed for eligibility, of whom 505 (73%) consented. Of these, 246 (49%) were allocated to the RISKIT-CJS intervention and 259 (51%) were allocated to treatment as usual only. At month 12, the overall follow-up rate was 57%: 55% in the RISKIT-CJS arm and 59% in the treatment-as-usual arm. At month 12, we observed an increase in per cent days abstinent from substances in both arms of the study, from 61% to 85%, but there was no evidence that the RISKIT-CJS intervention was superior to treatment as usual. A similar pattern was observed for secondary outcomes. The RISKIT-CJS intervention was not found to be any more cost-effective than treatment as usual. The qualitative research indicated that young people were positive about learning new skills and acquiring new knowledge. Although stakeholders considered the intervention worthwhile, they expressed concern that it came too late for the target population.

Limitations

Our original aim to collect data on offences was thwarted by the onset of the COVID-19 pandemic, and this affected both the statistical and economic analyses. Although 214 (87%) of the 246 participants allocated to the RISKIT-CJS intervention attended at least one individual face-to-face session, 98 (40%) attended a group session and only 47 (19%) attended all elements of the intervention.

Conclusions

The RISKIT-CJS intervention was no more clinically effective or cost-effective than treatment as usual in reducing substance use among adolescents involved in the criminal justice system.

Future research

The RISKIT-CJS intervention was considered more acceptable, and adherence was higher, in pupil referral units and substance misuse teams than in youth offending teams. Stakeholders in youth offending teams thought that the intervention was too late in the trajectory for their population.

Trial registration

This trial is registered as ISRCTN77037777.

Funding

This project was funded by the National Institute for Health and Care Research (NIHR) Public Health Research programme and will be published in full in Public Health Research; Vol. 11, No. 3. See the NIHR Journals Library website for further project information.

State Cannabis Legalization and Psychosis-Related Health Care Utilization

Importance

Psychosis is a hypothesized consequence of cannabis use. Legalization of cannabis could therefore be associated with an increase in rates of health care utilization for psychosis.

Objective

To evaluate the association of state medical and recreational cannabis laws and commercialization with rates of psychosis-related health care utilization.

Design, Setting, and Participants

Retrospective cohort design using state-level panel fixed effects to model within-state changes in monthly rates of psychosis-related health care claims as a function of state cannabis policy level, adjusting for time-varying state-level characteristics and state, year, and month fixed effects. Commercial and Medicare Advantage claims data for beneficiaries aged 16 years and older in all 50 US states and the District of Columbia, 2003 to 2017 were used. Data were analyzed from April 2021 to October 2022.

Exposure

State cannabis legalization policies were measured for each state and month based on law type (medical or recreational) and degree of commercialization (presence or absence of retail outlets).

Main Outcomes and Measures

Outcomes were rates of psychosis-related diagnoses and prescribed antipsychotics.

Results

This study included 63 680 589 beneficiaries followed for 2 015 189 706 person-months. Women accounted for 51.8% of follow-up time with the majority of person-months recorded for those aged 65 years and older (77.3%) and among White beneficiaries (64.6%). Results from fully-adjusted models showed that, compared with no legalization policy, states with legalization policies experienced no statistically significant increase in rates of psychosis-related diagnoses (medical, no retail outlets: rate ratio [RR], 1.13; 95% CI, 0.97-1.36; medical, retail outlets: RR, 1.24; 95% CI, 0.96-1.61; recreational, no retail outlets: RR, 1.38; 95% CI, 0.93-2.04; recreational, retail outlets: RR, 1.39; 95% CI, 0.98-1.97) or prescribed antipsychotics (medical, no retail outlets RR, 1.00; 95% CI, 0.88-1.13; medical, retail outlets: RR, 1.01; 95% CI, 0.87-1.19; recreational, no retail outlets: RR, 1.13; 95% CI, 0.84-1.51; recreational, retail outlets: RR, 1.14; 95% CI, 0.89-1.45). In exploratory secondary analyses, rates of psychosis-related diagnoses increased significantly among men, people aged 55 to 64 years, and Asian beneficiaries in states with recreational policies compared with no policy.

Conclusions and Relevance

In this retrospective cohort study of commercial and Medicare Advantage claims data, state medical and recreational cannabis policies were not associated with a statistically significant increase in rates of psychosis-related health outcomes. As states continue to introduce new cannabis policies, continued evaluation of psychosis as a potential consequence of state cannabis legalization may be informative.

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.

Correlates of psychotic like experiences (PLEs) during Pandemic: An online study investigating a possible link between the SARS-CoV-2 infection and PLEs among adolescents

BACKGROUND

This study investigated whether SARS-CoV-2 infection, depression, anxiety, sleep problems, cigarette, alcohol, drug usage contribute to psychotic-like experiences (PLEs) among adolescents during the pandemic. We also aimed to explore whether baseline inflammatory markers or the number of SARS-CoV-2-related symptoms are associated with PLEs, and the latter is mediated by internalizing symptoms.

METHODS

Altogether, 684 adolescents aged 12-18 (SARS-CoV-2 group n = 361, control group (CG) n = 323) were recruited. The Community Assessment of Psychic Experiences-42-Positive Dimension (CAPE-Pos), Patient Health Questionnaire-9 (PHQ-9), Generalized Anxiety Disorder-7 (GAD-7), and Pittsburg Sleep Quality Index (PSQI) questionnaires were completed by all volunteers using an online survey. C-reactive Protein and hemogram values, and SARS-CoV-2-related symptoms during the acute infection period were recorded in the SARS-CoV-2 group. Group comparisons, correlations, logistic regression, and bootstrapped mediation analyses were performed.

RESULTS

CAPE-Pos-Frequency/Stress scores were significantly higher, whereas GAD-7-Total and PSQI-Total scores were significantly lower in SARS-CoV-2 than CG. Among the SARS-CoV-2 group, monocyte count and the number of SARS-CoV-2-symptoms were positively correlated with CAPE-Pos-Frequency/Stress scores. Besides SARS-CoV-2, cigarette use, GAD-7, and PHQ-9 scores significantly contributed to the presence of at least one CAPE-Pos "often" or "almost always". PHQ-9 and GAD-7 fully mediated the relationship between the number of SARS-CoV-2 symptoms and CAPE-Pos-Frequency.

CONCLUSIONS

This study is the first to show a possible relationship between SARS-CoV-2 infection and PLEs among adolescents. Depression, anxiety, and cigarette use also contributed to PLEs. The number of SARS-Cov-2-symptoms and PLEs association was fully mediated by internalizing symptoms, but prospective studies will need to confirm this result.

Minimizing policy-biased appraisals of the evidence on cannabis and psychosis

Appraisals of the evidence on the relationship between cannabis use and psychosis are often biased by appraisers' pre-existing views on whether adult cannabis use should or should not be legal. This viewpoint gives examples of such policy-biased appraisals and suggests strategies for avoiding them.

Differential trajectories of tobacco smoking in people at ultra-high risk for psychosis: Associations with clinical outcomes

OBJECTIVE

People at ultra-high risk (UHR) for psychosis have a high prevalence of tobacco smoking, and rates are even higher among the subgroup that later develop a psychotic disorder. However, the longitudinal relationship between the course of tobacco smoking and clinical outcomes in UHR subjects is unknown.

METHODS

We investigated associations between tobacco smoking and clinical outcomes in a prospective study of UHR individuals (n = 324). Latent class mixed model analyses were used to identify trajectories of smoking severity. Mixed effects models were applied to investigate associations between smoking trajectory class and the course of attenuated psychotic symptoms (APS) and affective symptoms, as assessed using the CAARMS.

RESULTS

We identified four different classes of smoking trajectory: (i) Persistently High (n = 110), (ii) Decreasing (n = 29), (iii) Persistently Low (n = 165) and (iv) Increasing (n = 20). At two-year follow-up, there had been a greater increase in APS in the Persistently High class than for both the Persistently Low (ES = 9.77, SE = 4.87, p = 0.046) and Decreasing (ES = 18.18, SE = 7.61, p = 0.018) classes. There were no differences between smoking classes in the incidence of psychosis. There was a greater reduction in the severity of emotional disturbance and general symptoms in the Decreasing class than in the High (ES = -10.40, SE = 3.41, p = 0.003; ES = -22.36, SE = 10.07, p = 0.027), Increasing (ES = -11.35, SE = 4.55, p = 0.014; ES = -25.58, SE = 13.17, p = 0.050) and Low (ES = -11.38, SE = 3.29, p = 0.001; ES = -27.55, SE = 9.78, p = 0.005) classes, respectively.

CONCLUSIONS

These findings suggests that in UHR subjects persistent tobacco smoking is associated with an unfavorable course of psychotic symptoms, whereas decrease in the number of cigarettes smoked is associated with improvement in affective symptoms. Future research into smoking cessation interventions in the early stages of psychoses is required to shine light on the potential of modifying smoking behavior and its relation to clinical outcomes.

Examining pathways between genetic liability for schizophrenia and patterns of tobacco and cannabis use in adolescence

BACKGROUND

It is not clear to what extent associations between schizophrenia, cannabis use and cigarette use are due to a shared genetic etiology. We, therefore, examined whether schizophrenia genetic risk associates with longitudinal patterns of cigarette and cannabis use in adolescence and mediating pathways for any association to inform potential reduction strategies.

METHODS

Associations between schizophrenia polygenic scores and longitudinal latent classes of cigarette and cannabis use from ages 14 to 19 years were investigated in up to 3925 individuals in the Avon Longitudinal Study of Parents and Children. Mediation models were estimated to assess the potential mediating effects of a range of cognitive, emotional, and behavioral phenotypes.

RESULTS

The schizophrenia polygenic score, based on single nucleotide polymorphisms meeting a training-set p threshold of 0.05, was associated with late-onset cannabis use (OR = 1.23; 95% CI = 1.08,1.41), but not with cigarette or early-onset cannabis use classes. This association was not mediated through lower IQ, victimization, emotional difficulties, antisocial behavior, impulsivity, or poorer social relationships during childhood. Sensitivity analyses adjusting for genetic liability to cannabis or cigarette use, using polygenic scores excluding the CHRNA5-A3-B4 gene cluster, or basing scores on a 0.5 training-set p threshold, provided results consistent with our main analyses.

CONCLUSIONS

Our study provides evidence that genetic risk for schizophrenia is associated with patterns of cannabis use during adolescence. Investigation of pathways other than the cognitive, emotional, and behavioral phenotypes examined here is required to identify modifiable targets to reduce the public health burden of cannabis use in the population.

Variations of cannabis-related adverse mental health and addiction outcomes across adolescence and adulthood: A scoping review

INTRODUCTION

Evidence supporting associations between cannabis use and many health outcomes is growing, however it remains unclear how such associations vary across the lifespan. We therefore aim to answer the following questions: (1) Are the risks of cannabis's adverse effects on mental health and addiction-related outcomes different in adolescents than in adults? (2) What are the relationships between these cannabis's adverse effects and (a) an individual's age at first cannabis use, (b) age at assessment, and (c) duration of cannabis use?

METHODS

We searched Medline, Embase, CINAHL, and PsychINFO from inception to 18 October 2021. Two reviewers independently screened studies and descriptively synthesized results.

RESULTS

We included 140 studies. Cannabis effects on mental health and addiction-related outcomes were worse in adolescents, early cannabis initiators and cannabis users who consumed for longest periods. Evidence of worse long-term adverse effects in adolescents was substantial for psychosis, cannabis, and nicotine use disorders; mixed for depression, suicidality, other substance use and disorders; and limited for anxiety. Additionally, acute cannabis exposure had the opposite trend with adults more often reporting adverse effects than adolescents.

CONCLUSION

The available evidence suggests that cannabis use should be delayed as late as possible in adulthood and shortened in duration across the lifespan to decrease the risk of negative outcomes, while emphasizing the need for adapted harm reduction approaches. This scoping review provides evidence on the role of age and duration of exposure as determinants of cannabis-related adverse effects, which may inform prevention and harm reduction strategies.

SYSTEMATIC REVIEW REGISTRATION

https://doi.org/10.17605/OSF.IO/BYG72.

Brief Report: Suspected Cannabis-Induced Mania and Psychosis in Young Adult Males with Autism Spectrum Disorder

There is increasing interest in investigating cannabis for behavioral symptoms in individuals with autism spectrum disorder (ASD). The potential role of dysregulated cannabinoid signaling contributing to the pathophysiology of ASD is an area of active investigation. Results from retrospective and uncontrolled trials of cannabis in subjects with ASD have been published, reporting both potential benefits and adverse effects. Here, we describe the clinical course of three young adult males with ASD who developed mania or psychosis after the consistent use of cannabidiol and delta-9-tetrahydrocannabinol. Caution should be utilized with cannabis use in individuals with ASD until large-scale, replicated randomized controlled trials demonstrating efficacy, safety and tolerability have been published.

Cannabis and tobacco use prior to pregnancy and subsequent offspring birth outcomes: a 20-year intergenerational prospective cohort study

There is increasing evidence that the life-course origins of health and development begin before conception. We examined associations between timing and frequency of preconception cannabis and tobacco use and next generation preterm birth (PTB), low birth weight (LBW) and small for gestational age. 665 participants in a general population cohort were repeatedly assessed on tobacco and cannabis use between ages 14-29 years, before pregnancy. Associations were estimated using logistic regression. Preconception parent (either maternal or paternal) daily cannabis use age 15-17 was associated with sixfold increases in the odds of offspring PTB (aOR 6.65, 95% CI 1.92, 23.09), and offspring LBW (aOR 5.84, 95% CI 1.70-20.08), after adjusting for baseline sociodemographic factors, parent sex, offspring sex, family socioeconomic status, parent mental health at baseline, and concurrent tobacco use. There was little evidence of associations with preconception parental cannabis use at other ages or preconception parental tobacco use. Findings support the hypothesis that the early life origins of growth begin before conception and provide a compelling rationale for prevention of frequent use during adolescence. This is pertinent given liberalisation of cannabis policy.

Genetic overlap and causal associations between smoking behaviours and mental health

Cigarette smoking is a modifiable behaviour associated with mental health. We investigated the degree of genetic overlap between smoking behaviours and psychiatric traits and disorders, and whether genetic associations exist beyond genetic influences shared with confounding variables (cannabis and alcohol use, risk-taking and insomnia). Second, we investigated the presence of causal associations between smoking initiation and psychiatric traits and disorders. We found significant genetic correlations between smoking and psychiatric disorders and adult psychotic experiences. When genetic influences on known covariates were controlled for, genetic associations between most smoking behaviours and schizophrenia and depression endured (but not with bipolar disorder or most psychotic experiences). Mendelian randomization results supported a causal role of smoking initiation on psychiatric disorders and adolescent cognitive and negative psychotic experiences, although not consistently across all sensitivity analyses. In conclusion, smoking and psychiatric disorders share genetic influences that cannot be attributed to covariates such as risk-taking, insomnia or other substance use. As such, there may be some common genetic pathways underlying smoking and psychiatric disorders. In addition, smoking may play a causal role in vulnerability for mental illness.

Latent Class Mediation: A Comparison of Six Approaches

Latent class mediation modeling is designed to estimate the mediation effect when both the mediator and the outcome are latent class variables. We suggest using an adjusted one-step approach in which the latent class models for the mediator and the outcome are estimated first to decide on the number of classes, then the latent class models and the mediation model are jointly estimated. We present both an empirical demonstration and a simulation study to compare the performance of this one-step approach to a standard three-step approach with modal assignment (modal) and four different modern three-step approaches. Results from the study indicate that unadjusted modal, which ignores the classification errors of the latent class models, produced biased mediation effects. On the other hand, the adjusted one-step approach and the modern three-step approaches performed well with respect to bias for estimating mediation effects, regardless of measurement quality (i.e., model entropy) and latent class size. Among the three-step approaches we investigated, the maximum likelihood method with modal assignment and the BCH correction with robust standard error estimators are good alternatives to the adjusted one-step approach, given their unbiased standard error estimations.

A systematic review of longitudinal studies investigating the impact of cannabis use in patients with psychotic disorders

Introduction: Research has established a link between cannabis use and adverse psychotic outcomes in psychosis patients. However, we have yet to determine if this relationship is maintained when controlling for important confounding variables. The following systematic review aims to investigate if the association between cannabis use and psychotic outcomes is preserved when accounting for important confounders, and if discontinued use mitigates any potential negative impacts.Areas covered: The authors conducted an exhaustive search of the MEDLINE database and Google Scholar to identify articles pertaining to the systematic review. Thirty-three articles were retained for meeting the eligibility criteria.Expert opinion: The evidence confirms an overarching pattern of negative psychotic outcomes of cannabis intake in psychosis populations, even when accounting for crucial confounders. Psychosis patients should be informed with evidence-based health information regarding the effects of cannabis use. Clinicians should systematically evaluate cannabis intake patterns in psychosis patients and offer intervention services geared toward reducing problematic consumption. Researchers should record confounding factors in a more systematic manner in future longitudinal investigations while paying careful attention to the potency and dose-response effects of the ingested cannabis. Deciders will need to investigate the impact of cannabis regulations on psychosis populations.

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.

Does an association between cigarette smoking and Parkinson's Disease-related psychosis exist? Insights from a large non-demented cohort

BACKGROUND

Parkinson's Disease-related Psychosis (PDP) encompasses a spectrum of symptoms ranging from "minor" hallucinations to formed hallucinations and delusions. Notably, cognitive impairment has been recognized as the strongest risk factor for PDP. Several evidences suggest a possible role of cigarette smoking in both cognition and psychotic syndromes.

OBJECTIVES

To evaluate the possible independent association between cigarette smoking and PDP in a large cohort of non-demented PD patients.

METHODS

A cohort of non-demented PD patients was selected from the FRAGAMP study population. All participants underwent a standardised structured questionnaire to assess demographic, clinical and environmental exposure data. Clinical features were assessed using UPDRS, HY stage, AIMS, MMSE and Hamilton Rating Scale for Depression. Presence of psychotic symptoms was assessed using UPDRS-I.2 score. Diagnosis of PDP was made according to NINDS/NIMH criteria.

RESULTS

Four hundred eighty-five non-demented PD patients were enrolled [292 men (60.2%); mean age ± SD 65.6 ± 9.8]. Among them, 28 (5.8%) had PDP. Multivariate analysis, adjusting by HY stage, MMSE and LED, shown an independent association between PDP and "nightmares-abnormal movements during sleep" and current smoking [adjOR 7.39 (95%CI 1.45-37.69; P-value 0.016)].

CONCLUSIONS

Our findings provide interesting insights about the possible role of current smoking in facilitating the occurrence of psychotic symptoms in PD.

Psychotic Experiences and Schizotypy in Early Adolescence Predict Subsequent Suicidal Ideation Trajectories and Suicide Attempt Outcomes From Age 18 to 38 Years

Subclinical risk markers for schizophrenia predict suicidality, but little is known about the nature of the relationship. Suicidal ideation is often considered homogenous, but distinguishing passive from active ideation (ie, thoughts of death vs thoughts of killing oneself) and different temporal patterns may further the understanding of risk factors. We tested whether schizotypy and psychotic experiences (PEs) in early adolescence predict subsequent growth trajectories of suicidal ideation and suicide attempt outcomes. Participants were 1037 members of the population-representative Dunedin Study cohort. PE was measured at 11 years and schizotypy at 13 and 15 years. Outcomes were passive and active suicidal ideation, and suicide attempt, measured at 18, 21, 26, 32, and 38 years. Passive ideation was best represented by 2 trajectories, including persistent and transient ideation classes. Schizotypy predicted membership in the smaller persistent class (odds ratio [OR] = 1.21, P = .041), whereas PE was not associated with class membership. The probability of suicide attempts was 13.8% in the persistent ideation class, compared with 1.8% in the transient class. Active ideation was best represented by a 1-class model, the intercept of which was predicted by schizotypy (OR = 1.23, P = .015). Suicide attempts were predicted by schizotypy (OR = 1.53, P = .040) and PE (OR = 3.42, P = .046), and this was partially mediated by indirect effects via the active ideation trajectory. Findings indicate that adolescent schizotypy and PE are related to subsequent suicidal ideation and attempts. Suicidal ideation is heterogeneous, and schizotypy is specifically related to a persistent passive ideation subgroup.

High genes: Genetic underpinnings of cannabis use phenotypes

Cannabis is one of the most widely used substances across the globe and its use has a substantial heritable component. However, the heritability of cannabis use varies according to substance use phenotype, suggesting that a unique profile of gene variants may contribute to the different stages of use, such as age of use onset, lifetime use, cannabis use disorder, and withdrawal and craving during abstinence. Herein, we review a subset of genes identified by candidate gene, family-based linkage, and genome-wide association studies related to these cannabis use phenotypes. We also describe their relationships with other substances, and their functions at the neurobiological, cognitive, and behavioral levels to hypothesize the role of these genes in cannabis use risk. Delineating genetic risk factors in the various stages of cannabis use will provide insight into the biological mechanisms related to cannabis use and highlight points of intervention prior to and following the development of dependence, as well as identify targets to aid drug development for treating problematic cannabis use.

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.

Individualized prediction of 2-year risk of relapse as indexed by psychiatric hospitalization following psychosis onset: Model development in two first episode samples

BACKGROUND

Although most patients with psychotic disorders experience relapse, it is not possible to predict whether or when an individual patient is going to relapse. We aimed to develop a multifactorial risk prediction algorithm for predicting risk of relapse in first episode psychosis (FEP).

METHODS

Data from two prospectively collected cohorts of FEP patients (N = 1803) were used to develop three multiple logistic prediction models to predict risk of relapse (defined as hospitalization) within the first 2 years of onset of psychosis. Model 1 (M1_S1) used data obtained from clinical notes (Sample 1) while model 2 (M2_S2) applied the same set of predictors using data obtained from research interviews (Sample 2). The final model (Sample 2: M3_S2) used the same predictors plus additional detailed information on predictors. Model performance was evaluated employing measures of overall accuracy, calibration, discrimination and internal validation.

RESULTS

In both samples, the 2-year probability of psychiatric hospitalization was 37%. Of all the models, discrimination accuracy was lowest when limited information (such as socio-demographic and clinical parameters) was included in the prediction model. Model M3_S2 using additional information (descriptors of pattern of cannabis, nicotine, alcohol and other illicit drug use) obtained from research interview had the best discrimination accuracy (Harrell's C index 0.749).

CONCLUSIONS

The measures that contributed most to predicting hospitalization are readily accessible in routine clinical practice, suggesting that a risk prediction tool based on these models would be clinically practicable following validation in independent samples and permit a personalized approach to relapse prevention in psychosis.

Risk Factors for Cannabis-Related Mental Health Harms in Older Adults: A Review

Objectives: This paper reviews research on the topic of cannabis use and mental health harms in older adults and illustrates potential contributing factors and special clinical considerations for working with this population. Known risk factors for cannabis-related mental disorders and mental health problems are outlined, first for the general population and then specifically for older adults. Methods: Studies were identified through online databases using a variety of search words. Articles were included in the review if they were peer-reviewed or published by a reputable national organization, published in English, and were pertinent to the topic of mental health harms of cannabis use. Results: Risk factors that emerged from the literature review aligned with the following categories: (1) patterns of use (i.e., potency of product, frequency of use), (2) personal characteristics (i.e., age, sex, social demographics), (3) psychosocial constructs (motivations, perceptions), and (4) morbidities (mental health, medication interactions). Conclusions: Frequent use was associated with increased risk for mental health consequences related to cannabis use. Certain motives for use (i.e., using to cope, using as a sleep aid) may increase susceptibility to cannabis-related harms, although more empirical work is required. Mental health conditions may predispose to cannabis-related harms through a variety of mechanisms, including increased vulnerability for cannabis-related psychiatric disorders, poorer prognosis for preexisting psychiatric disorders, and possibility of cannabis-medication interactions. Personal characteristics (younger age, being male, lower socioeconomic status) predict more frequent cannabis use, which may dispose to adverse outcomes. Clinical Implications: Predictors of cannabis-related harms hold relevance for public health messaging, as well as clinical interventions. Understanding how cannabis interacts with sociodemographic factors, mental health morbidities, and medications is crucial in providing accurate guidance to patients about their recreational cannabis use and in informing prescriber decisions about medicinal cannabis.

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.

Adolescent Substance Use and the Brain: Behavioral, Cognitive and Neuroimaging Correlates

Adolescence is an important ontogenetic period that is characterized by behaviors such as enhanced novelty-seeking, impulsivity, and reward preference, which can give rise to an increased risk for substance use. While substance use rates in adolescence are generally on a decline, the current rates combined with emerging trends, such as increases in e-cigarette use, remain a significant public health concern. In this review, we focus on the neurobiological divergences associated with adolescent substance use, derived from a cross-sectional, retrospective, and longitudinal studies, and highlight how the use of these substances during adolescence may relate to behavioral and neuroimaging-based outcomes. Identifying and understanding the associations between adolescent substance use and changes in cognition, mental health, and future substance use risk may assist our understanding of the consequences of drug exposure during this critical window.

Adolescent multiple risk behaviours cluster by number of risks rather than distinct risk profiles in the ALSPAC cohort

BACKGROUND

Experimentation with new behaviours during adolescence is normal. However, engagement in two or more risk behaviours, termed multiple risk behaviours is associated with socioeconomic disadvantage and poor health and social outcomes. Evidence of how adolescents cluster based on their risk behaviours is mixed.

METHODS

Latent Class Analysis was used to study patterns of engagement in 10 self-reported risk behaviours (including substance use, self-harm and sexual health) from the Avon Longitudinal Study of Parents and Children (ALSPAC) cohort at ages 15-16 years. Data was available for 6556 adolescents. Associations between risk profile and sex were explored.

RESULTS

A 3-class model for both females and males was deemed to have acceptable fit. Whilst we found evidence of a sex difference in the risk behaviours reported within each class, the sex-specific results were very similar in many respects. For instance, the prevalence of membership of the high-risk class was 8.5% for males and 8.7% for females and both groups had an average of 5.9 behaviours. However, the classes were both statistically dubious, with class separation (entropy) being poor as well as conceptually problematic, because the resulting classes did not provide distinct profiles and varied only by quantity of risk-behaviours.

CONCLUSION

Clusters of adolescents were not characterised by distinct risk behaviour profiles, and provide no additional insight for intervention strategies. Given this is a more complicated, software-specific method, we conclude that an equally effective, but more readily replicable approach is to use a count of the number of risk behaviours.

Modes of delivery in concurrent nicotine and cannabis use ("co-use") among youth: Findings from the International Tobacco Control (ITC) Survey

BACKGROUND

Cannabis use is more common among nicotine users than non-users. This study characterized concurrent use of nicotine and cannabis ("co-use") among 12,064 youth aged 16-19 years residing in Canada, the United States, and England in 2017. Methods: Data were from the ITC Youth Tobacco & Vaping Survey (Wave 1). Seven modes of cannabis delivery (MOD) were characterized by country of residence and past 30-day use of combusted tobacco and electronic cigarettes. Weighted multivariable regression models were fitted to assess the correlates of co-use and each cannabis MOD. Results: Seventy percent of cannabis users reported nicotine use. Co-users exhibited behavioral and demographic differences compared to exclusive users of either substance. "Smoking cannabis without tobacco" was the most popular form of use (78%). Use of nicotine-containing e-cigarettes was associated with "using an e-cigarette to vape cannabis oil/liquid" (aOR: 4.96, 95%CI: 2.23-11.06). Combustible tobacco use was associated with "smoking cannabis with tobacco in a joint/blunt" (aOR: 2.93, 95%CI: 1.89-4.56). Country-level differences were detected. Conclusions: Nicotine use is substantial among cannabis users, and associations exist between modes of delivery for both drugs. Results underscore the importance of studying cannabis and nicotine use concurrently, and the need to address the use of both substances in developing interventions for youth users.

Cannabis Use and the Risk for Psychosis and Affective Disorders

Objective: This review discusses the relationship between cannabis use and psychotic, bipolar, depressive, and anxiety disorders, as well as suicide. It summarizes epidemiological evidence from cross-sectional and long-term prospective studies and considers possible etiological mechanisms. Methods: Systematic reviews and methodologically robust studies in the field (from inception to February 2019) were identified using a comprehensive search of Medline, PsychINFO, and Embase and summarized using a narrative synthesis. Results: Consistent evidence, both from observational and experimental studies, has confirmed the important role of cannabis use in the initiation and persistence of psychotic disorders. The size of the effect is related to the extent of cannabis use, with greater risk for early cannabis use and use of high-potency varieties and synthetic cannabinoids. Accumulating evidence suggests that frequent cannabis use also increases the risk for mania as well as for suicide. However, the effect on depression is less clear and findings on anxiety are contradictory with only a few methodologically robust studies. Furthermore, the relationship with common mental disorders may involve reverse causality, as depression and anxiety are reported to lead to greater cannabis consumption in some studies. Pathogenetic mechanisms focus on the effect of tetrahydrocannabinol (THC, the main psychoactive ingredient of cannabis) interacting with genetic predisposition and perhaps other environmental risk factors. Cannabidiol (CBD), the other important ingredient of traditional cannabis, ameliorates the psychotogenic effects of THC but is absent from the high-potency varieties that are increasingly available. Conclusions: The evidence that heavy use of high-THC/low-CBD types of cannabis increases the risk of psychosis is sufficiently strong to merit public health education. Evidence of similar but smaller effects in mania and suicide is growing, but is not convincing for depression and anxiety. There is much current interest in the possibility that CBD may be therapeutically useful.

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.

Childhood abuse and psychotic experiences in adulthood: findings from a 35-year longitudinal study

BACKGROUND

The extent to which exposure to childhood sexual and physical abuse increases the risk of psychotic experiences in adulthood is currently unclear.AimsTo examine the relationship between childhood sexual and physical abuse and psychotic experiences in adulthood taking into account potential confounding and time-dynamic covariate factors.

METHOD

Data were from a cohort of 1265 participants studied from birth to 35 years. At ages 18 and 21, cohort members were questioned about childhood sexual and physical abuse. At ages 30 and 35, they were questioned about psychotic experiences (symptoms of abnormal thought and perception). Generalised estimating equation models investigated covariation of the association between abuse exposure and psychotic experiences including potential confounding factors in childhood (socioeconomic disadvantage, adverse family functioning) and time-dynamic covariate factors (mental health, substance use and life stress).

RESULTS

Data were available for 962 participants; 6.3% had been exposed to severe sexual abuse and 6.4% to severe physical abuse in childhood. After adjustment for confounding and time-dynamic covariate factors, those exposed to severe sexual abuse had rates of abnormal thought and abnormal perception symptoms that were 2.25 and 4.08 times higher, respectively than the 'no exposure' group. There were no significant associations between exposure to severe physical abuse and psychotic experiences.

CONCLUSIONS

Findings indicate that exposure to severe childhood sexual (but not physical) abuse is independently associated with an increased risk of psychotic experiences in adulthood (particularly symptoms of abnormal perception) and this association could not be fully accounted for by confounding or time-dynamic covariate factors.Declaration of interestNone.

A Twin Study on the Association Between Psychotic Experiences and Tobacco Use During Adolescence

OBJECTIVE

Psychotic experiences (PE) are dimensional phenomena in the general population that resemble psychotic symptoms, such as paranoia and hallucinations. This is the first twin study to explore the degree to which tobacco use and PE share genetic or environmental influences. Previous studies on the association between adolescent tobacco use and PE have not considered PE dimensionally, included negative symptoms, or accounted for confounding by sleep disturbance and stressful life events.

METHOD

An unselected adolescent twin sample (N = 3,787 pairs; mean age = 16.16 years) reported on PE (paranoia, hallucinations, cognitive disorganization, grandiosity, and anhedonia) and regularity of tobacco use. Parents rated the twins' negative symptoms. Regression analyses were conducted while adjusted for sociodemographic characteristics, prenatal maternal smoking, cannabis use, sleep disturbance, and stressful life events. Bivariate twin modeling was used to estimate the degree of genetic and common and unique environmental influences shared between tobacco use and PE.

RESULTS

Regular smokers were significantly more likely to experience paranoia, hallucinations, cognitive disorganization, and negative symptoms (β = 0.17-0.34), but not grandiosity or anhedonia, than nonsmokers, after adjustment for confounders. Paranoia, hallucinations, and cognitive disorganization correlated ≥0.15 with tobacco use (r = 0.15-0.21, all p < .001). Significant genetic correlations (r_A=0.37-0.45) were found. Genetic influences accounted for most of the association between tobacco use and paranoia (84%) and cognitive disorganization (81%). Familial influences accounted for 80% of the association between tobacco use and hallucinations.

CONCLUSION

Tobacco use and PE during adolescence were associated after adjustment for confounders. They appear to co-occur largely because of shared genetic influences.

Genetic Predisposition vs Individual-Specific Processes in the Association Between Psychotic-like Experiences and Cannabis Use

Importance

Previous research indicates that cannabis use is associated with psychotic-like experiences (PLEs). However, it is unclear whether this association results from predispositional (ie, shared genetic) factors or individual-specific factors (eg, causal processes, such as cannabis use leading to PLEs).

Objectives

To estimate genetic and environmental correlations between cannabis use and PLEs, and to examine PLEs in twin and nontwin sibling pairs discordant for exposure to cannabis use to disentangle predispositional from individual-specific effects.

Design, Setting, and Participants

In this cross-sectional analysis, diagnostic interviews and self-reported data were collected from 2 separate population-based samples of twin and nontwin sibling pairs. Data from the Human Connectome Project were collected between August 10, 2012, and September 29, 2015, and data from the Australian Twin Registry Cohort 3 (ATR3) were collected between August 1, 2005, and August 31, 2010. Data were analyzed between August 17, 2017, and July 6, 2018. The study included data from 1188 Human Connectome Project participants and 3486 ATR3 participants, totaling 4674 participants.

Main Outcomes and Measures

Three cannabis-involvement variables were examined: frequent use (ie, ≥100 times), a DSM-IV lifetime cannabis use disorder diagnosis, and current cannabis use. Genetic and environmental correlations between cannabis involvement and PLEs were estimated. Generalized linear mixed models examined PLE differences in twin and nontwin sibling pairs discordant for cannabis use.

Results

Among the 4674 participants, the mean (SD) age was 30.5 (3.2) years, and 2923 (62.5%) were female. Data on race/ethnicity were not included as a covariate owing to lack of variability within the ATR3 sample; among the 1188 participants in the Human Connectome Project, 875 (73.7%) were white. Psychotic-like experiences were associated with frequent cannabis use (β = 0.11; 95% CI, 0.08-0.14), cannabis use disorder (β = 0.13; 95% CI, 0.09-0.16), and current cannabis use (β = 0.07; 95% CI, 0.04-0.10) even after adjustment for covariates. Correlated genetic factors explained between 69.2% and 84.1% of this observed association. Within discordant pairs of twins/siblings (Npairs, 308-324), Psychotic-like experiences were more common in cannabis-exposed individuals compared with their relative who used cannabis to a lesser degree (β ≥ .23, P < .05; eg, frequent and infrequent cannabis-using relatives significantly differed, z = -5.41; P < .001).

Conclusions and Relevance

Despite the strong contribution of shared genetic factors, frequent and problem cannabis use also appears to be associated with PLEs via person-specific pathways. This study's findings suggest that policy discussions surrounding legalization should consider the influence of escalations in cannabis use on traitlike indices of vulnerability, such as PLEs, which could contribute to pervasive psychological and interpersonal burden.