Cannabis use and age at onset of psychosis: further evidence of interaction with COMT Val158Met polymorphism

Clinical and cognitive outcomes in first-episode psychosis: focus on the interplay between cannabis use and genetic variability in endocannabinoid receptors

Introduction

Research data show the impact of the endocannabinoid system on psychosis through its neurotransmission homeostatic functions. However, the effect of the endocannabinoid system genetic variability on the relationship between cannabis use and psychosis has been unexplored, even less in first-episode patients. Here, through a case-only design, we investigated the effect of cannabis use and the genetic variability of endocannabinoid receptors on clinical and cognitive outcomes in first-episode psychosis (FEP) patients.

Methods

The sample comprised 50 FEP patients of European ancestry (mean age (sd) = 26.14 (6.55) years, 76% males), classified as cannabis users (58%) or cannabis non-users. Two Single Nucleotide Polymorphisms (SNP) were genotyped at the cannabinoid receptor type 1 gene (CNR1 rs1049353) and cannabinoid receptor type 2 gene (CNR2 rs2501431). Clinical (PANSS, GAF) and neuropsychological (WAIS, WMS, BADS) assessments were conducted. By means of linear regression models, we tested the main effect of cannabis use and its interaction with the polymorphic variants on the clinical and cognitive outcomes.

Results

First, as regards cannabis effects, our data showed a trend towards more severe positive symptoms (PANSS, p = 0.05) and better performance in manipulative abilities (matrix test-WAIS, p = 0.041) among cannabis users compared to non-users. Second, concerning the genotypic effects, the T allele carriers of the CNR1 rs1049353 presented higher PANSS disorganization scores than CC homozygotes (p = 0.014). Third, we detected that the observed association between cannabis and manipulative abilities is modified by the CNR2 polymorphism (p = 0.022): cannabis users carrying the G allele displayed better manipulative abilities than AA genotype carriers, while the cannabis non-users presented the opposite genotype-performance pattern. Such gene-environment interaction significantly improved the overall fit of the cannabis-only model (Δ-R2 = 8.4%, p = 0.019).

Discussion

Despite the preliminary nature of the sample, our findings point towards the role of genetic variants at CNR1 and CNR2 genes in the severity of the disorganized symptoms of first-episode psychosis and modulating cognitive performance conditional to cannabis use. This highlights the need for further characterization of the combined role of endocannabinoid system genetic variability and cannabis use in the understanding of the pathophysiology of psychosis.

Acute effects of Δ9-tetrahydrocannabinol (THC) on resting state connectivity networks and impact of COMT genotype: A multi-site pharmacological fMRI study

BACKGROUND

Cannabis produces various acute psychotropic effects, with marked individual differences. Cannabis use is a risk factor for developing psychotic disorders. The main component responsible for these effects is Δ9-tetrahydrocannabinol (THC). Here we investigated the neural basis of acute THC effects and its modulation by catechol-methyl-transferase (COMT) Val158Met genotype.

METHODS

Resting state functional MRI data of healthy occasional cannabis users were combined and re-analyzed from three double-blind, placebo-controlled, within-subject pharmacological functional magnetic resonance imaging studies (total N=87). Functional connectivity after placebo and THC was compared in three functional networks (salience, executive and default mode network) and a network implicated in psychosis (the hippocampus-midbrain-striatum network). COMT genotype modulation of subjective effects and connectivity was examined.

RESULTS

THC reduced connectivity in the salience network, specifically from the right insula to both the left insula and anterior cingulate cortex. We found a trend towards decreased connectivity in the hippocampus-midbrain-striatum network after THC. COMT genotype modulated subjective effects of THC, with strongest dysphoric reactions in Met/Met individuals. In addition, reduced connectivity after THC was demonstrated in the hippocampus-midbrain-striatum network of Met/Met individuals only.

CONCLUSIONS

In this large multisite study we found that THC robustly decreases connectivity in the salience network, involved in processing awareness and salient information. Connectivity changes in the hippocampus-midbrain-striatum network may reflect the acute psychotic-like effects of THC. COMT genotype modulation of THC's impact on subjective effects and functional connectivity provides further evidence for involvement of prefrontal dopamine levels in the acute effects of cannabis.

The genetic basis of onset age in schizophrenia: evidence and models

Schizophrenia is a heritable neurocognitive disorder affecting about 1% of the population, and usually has an onset age at around 21-25 in males and 25-30 in females. Recent advances in genetics have helped to identify many common and rare variants for the liability to schizophrenia. Earlier evidence appeared to suggest that younger onset age is associated with higher genetic liability to schizophrenia. Clinical longitudinal research also found that early and very-early onset schizophrenia are associated with poor clinical, neurocognitive, and functional profiles. A recent study reported a heritability of 0.33 for schizophrenia onset age, but the genetic basis of this trait in schizophrenia remains elusive. In the pre-Genome-Wide Association Study (GWAS) era, genetic loci found to be associated with onset age were seldom replicated. In the post-Genome-Wide Association Study era, new conceptual frameworks are needed to clarify the role of onset age in genetic research in schizophrenia, and to identify its genetic basis. In this review, we first discussed the potential of onset age as a characterizing/subtyping feature for psychosis, and as an important phenotypic dimension of schizophrenia. Second, we reviewed the methods, samples, findings and limitations of previous genetic research on onset age in schizophrenia. Third, we discussed a potential conceptual framework for studying the genetic basis of onset age, as well as the concepts of susceptibility, modifier, and "mixed" genes. Fourth, we discussed the limitations of this review. Lastly, we discussed the potential clinical implications for genetic research of onset age of schizophrenia, and how future research can unveil the potential mechanisms for this trait.

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.

Cannabis induced psychosis: a systematic review on the role of genetic polymorphisms

OBJECTIVE

Cannabis sativa is a recreational drug commonly consumed in Europe and is getting popularity for both recreational and therapeutic use. In some individuals, the use of cannabis leads to psychotic disorders. This systematic review summarizes the current evidence linking genetic polymorphisms and inter-individual susceptibility to psychosis induced by cannabis.

METHOD

Studies published from 2005 to 2020 were identified through Medline using PubMed, Web of Science and Scopus database and searches were conducted according to PRISMA guidelines. Initial search was performed with terms: "cannabis induced psychosis" AND "genetics".

RESULTS

From the initial group of 108 papers, 18 studies met our inclusion criteria. Many of the findings revealed associations with genetic polymorphisms modulations of genes involved directly (COMT, DRD2 and DAT) or indirectly (AKT1) to dopamine pathways. The most consistent finding was with COMT rs4680, where the presence of the Val allele was associated with a higher risk for cannabis-induced psychosis. This higher susceptibility was also reported for AKT1 (rs2494732) with the CC genotype. Of note, the only genome-wide association study identified a significant signal close to the cholinergic receptor muscarinic 3 represented by rs115455482 and rs74722579 predisposing to cannabis-induced hallucinations and remarkably no dopaminergic target was found.

CONCLUSION

Actual evidence supports the role of dopamine in cannabis induced psychosis. However, most of genetic polymorphism studies have as a starting point the pre-existing dopaminergic theoretical basis for psychosis. This alerts to the importance of more broad genetic studies. Integrate genetic results into biological systems may enhance our knowledge of cannabis induced psychosis and could help in the prevention and treatment of these patients.

Effects of Prenatal Nicotine, THC, or Co-Exposure on Cognitive Behaviors in Adolescent Male and Female Rats

INTRODUCTION

Although there has been a decrease in the prevalence of tobacco smoking, exposure to nicotine during pregnancy remains a substantial problem worldwide. Further, given the recent escalation in e-cigarette use and legalization of cannabis, it has become essential to understand the effects of nicotine and cannabinoid co-exposure during early developmental stages.

AIMS AND METHODS

We systematically examined the effects of nicotine and/or THC prenatal exposure on cognitive behaviors in male and female offspring. Dams were exposed to nicotine vape or vehicle, and oral edible THC or vehicle, throughout pregnancy. Adolescent offspring were then tested in the prepulse inhibition test, novel object recognition task, and novelty suppressed feeding task.

RESULTS

At birth, pups from mothers exposed to nicotine vape or oral THC exhibited reduced body weight, compared to control pups. Prenatal nicotine vape exposure resulted in a decreased baseline startle reactivity in adolescent male and female rats, and in females, enhanced sensorimotor gating in the prepulse inhibition test. Prenatal nicotine and THC co-exposure resulted in significant deficits in the prepulse inhibition test in males. Deficits in short-term memory were also found in males prenatally exposed to THC, either alone or with nicotine co-exposure, and in females exposed to THC alone. Finally, in males, a modest increase in anxiety-associated behaviors was found with THC or nicotine exposure in the latency to approach a novel palatable food.

CONCLUSIONS

These studies demonstrate differential effects of prenatal exposure to e-cigarette nicotine vape and/or edible THC on cognitive function, with differing effects within male and female groups.

IMPLICATIONS

These studies demonstrate an impact of nicotine, THC, or co-exposure during early developmental stages in utero on behavioral outcomes in adolescence. These findings have important translational implications given the continued use of nicotine and THC containing products by pregnant women worldwide, which can be applied to support healthcare and policy efforts restricting nicotine and THC use during pregnancy.

Cannabis, Schizophrenia Risk and Genetics: A Case Report of a Patient With Homozygous Valine Catechol-O-Methyltransferase Polymorphism

The question of whether cannabis can trigger schizophrenia continues to be a subject of interest. There has been an increasing focus on identifying potential genetic factors that may predispose cannabis users to develop schizophrenia. One such gene identified in many studies codes for a catechol-O-methyltransferase (COMT) enzyme polymorphism. These studies, however, are limited by the inclusion of patients displaying psychotic symptoms during cannabis intoxication and those who continue to display psychotic symptoms after its cessation. The latter is of interest in truly understanding the risk of cannabis triggering schizophrenia and more studies are needed to clarify the potential relationship. We present the case of a 24-year-old female who presented with psychotic symptoms and was diagnosed with schizophrenia after extensive cannabis use. In addition, she had a homozygous valine COMT polymorphism, a genetic variant thought to be associated with a predisposition for schizophrenia in cannabis users. We discuss the significance of our findings in understanding the relationship between cannabis use and the development of schizophrenia in genetically predisposed individuals.

Adolescent Neurodevelopment and Vulnerability to Psychosis

Adolescence is characterized by significant changes in several domains, including brain structure and function, puberty, and social and environmental factors. Some of these changes serve to increase the likelihood of psychosis onset during this period, while others may buffer this risk. This review characterizes our current knowledge regarding the unique aspects of adolescence that may serve as risk factors for schizophrenia spectrum disorders. In addition, we provide potential future directions for research into adolescent-specific developmental mechanisms that impart vulnerability to psychosis and the possibility of interventions that capitalize on adolescents' unique characteristics. Specifically, we explore the ways in which gray and white matter develop throughout adolescence in typically developing youth as well as in those with psychosis spectrum disorders. We also discuss current views on the function that social support and demands, as well as role expectations, play in risk for psychosis. We further highlight the importance of considering biological factors such as puberty and hormonal changes as areas of unique vulnerability for adolescents. Finally, we discuss cannabis use as a factor that may have a unique impact during adolescent neurodevelopment, and subsequently potentially impact psychosis onset. Throughout, we include discussion of resilience factors that may provide unique opportunities for intervention during this dynamic life stage.

Psychotic disorder and cannabis use: Canadian hospitalization trends, 2006-2015

INTRODUCTION

Given the recent and impending changes to the legal status of nonmedical cannabis use in Canada, understanding the effects of cannabis use on the health care system is important for evaluating the impact of policy change. The aim of this study was to examine pre-legalization trends in hospitalizations for mental and behavioural disorders due to the use of cannabis, according to demographics factors and clinical conditions.

METHODS

We assessed the total number of inpatient hospitalizations for psychiatric conditions with a primary diagnosis of a mental or behavioural disorder due to cannabis use (ICD-10-CA code F12) from the Hospital Mental Health Database for ten years spanning 2006 to 2015, inclusive. We included hospitalizations from all provinces and territories except Quebec. Rates (per 100 000 persons) and relative proportions of hospitalizations by clinical condition, age group, sex and year are reported.

RESULTS

Between 2006 and 2015, the rate of cannabis-related hospitalizations in Canada doubled. Of special note, however, is that hospitalizations during this time period for those with the clinical condition code "mental and behavioural disorders due to use of cannabinoids, psychotic disorder" (F12.5) tripled, accounting for almost half (48%) of all cannabis-related hospitalizations in 2015.

CONCLUSION

Further research is required to investigate the reasons for the increase in hospitalizations for cannabis-related psychotic disorder. The introduction of high-potency cannabinoid products and synthetic cannabinoids into the illicit market are considered as possible factors.

Factors Moderating the Association Between Cannabis Use and Psychosis Risk: A Systematic Review

Increasing evidence indicates a relationship between cannabis use and psychosis risk. Specific factors, such as determinants of cannabis use or the genetic profile of cannabis users, appear to moderate this association. The present systematic review presents a detailed and up-to-date literature overview on factors that influence the relationship between cannabis use and psychosis risk. A systematic search was performed according to the PRISMA guidelines in MEDLINE and Embase, and 56 studies were included. The results show that, in particular, frequent cannabis use, especially daily use, and the consumption of high-potency cannabis are associated with a higher risk of developing psychosis. Moreover, several genotypes moderate the impact of cannabis use on psychosis risk, particularly those involved in the dopamine function, such as AKT1. Finally, cannabis use is associated with an earlier psychosis onset and increased risk of transition in individuals at a clinical high risk of psychosis. These findings indicate that changing cannabis use behavior could be a harm reduction strategy employed to lower the risk of developing psychosis. Future research should aim to further develop specific biomarkers and genetic profiles for psychosis, thereby contributing to the identification of individuals at the highest risk of developing a psychotic disorder.

Determining Risks for Cannabis Use Disorder in the Face of Changing Legal Policies

Purpose of review

This review aims to summarize and critically evaluate the current literature on the associations between individual and socio-cultural factors that increase risk for cannabis use disorder (CUD), and policy change.

Recent findings

Epidemiological studies show that areas with permissive legal cannabis climates are associated with greater individual risk factors for CUD. This includes: (1) higher rates of edible consumption and vaping, (2) higher delta-9-tetrahydrocannabinol (THC) potency and lower cannabidiol (CBD) levels, and, (3) younger age of initiation of use.

Summary

A change in the socio-cultural level, such as shifts in the legalization of cannabis, could interact with individual-level factors in their associations with CUD. There is currently a lack of empirical studies that evaluate this interaction. We propose that future research consider a bioecological framework for CUD to allow for a comprehensive understanding of the effects of legal climate that could inform policy and clinical practice.

Trend level gene-gender interaction effect for the BDNF rs6265 variant on age of onset of psychosis

A BDNF rs6265 [A/A] by gender by cannabis use interaction has been associated with age of onset of psychosis (AoP). We examined the gender and cannabis use-adjusted association between BDNF rs6265 [G>A] and AKT1 rs2494732 [T>C] and AoP. Data from 167 Caucasians on AoP and age at first regular cannabis use were collected. Kaplan-Meier and Cox regression analyses were conducted. A trend level gene-gender interaction effect was observed for the BDNF rs6265 A/A genotype, controlling for age at first regular cannabis use. Larger collaborative research projects are required to further investigate this effect.

Acute effects of ∆9-tetrahydrocannabinol (THC) on resting state brain function and their modulation by COMT genotype

Cannabis produces a broad range of acute, dose-dependent psychotropic effects. Only a limited number of neuroimaging studies have mapped these effects by examining the impact of cannabis on resting state brain neurophysiology. Moreover, how genetic variation influences the acute effects of cannabis on resting state brain function is unknown. Here we investigated the acute effects of ∆9-tetrahydrocannabinol (THC), the main psychoactive constituent of cannabis, on resting state brain neurophysiology, and their modulation by catechol-methyl-transferase (COMT) Val158Met genotype. Thirty-nine healthy volunteers participated in a pharmacological MRI study, where we applied Arterial Spin Labelling (ASL) to measure perfusion and functional MRI to assess resting state connectivity. THC increased perfusion in bilateral insula, medial superior frontal cortex, and left middle orbital frontal gyrus. This latter brain area showed significantly decreased connectivity with the precuneus after THC administration. THC effects on perfusion in the left insula were significantly related to subjective changes in perception and relaxation. These findings indicate that THC enhances metabolism and thus neural activity in the salience network. Furthermore, results suggest that recruitment of brain areas within this network is involved in the acute effects of THC. Resting state perfusion was modulated by COMT genotype, indicated by a significant interaction effect between drug and genotype on perfusion in the executive network, with increased perfusion after THC in Val/Met heterozygotes only. This finding suggests that prefrontal dopamine levels are involved in the susceptibility to acute effects of cannabis.

The Effect of Age of Initiation of Cannabis Use on Psychosis, Depression, and Anxiety among Youth under 25 Years

OBJECTIVES

This study was conducted to review the current state of evidence on the association between age of initiation of cannabis use and symptoms of psychosis, depression, or anxiety among youth under 25 years of age.

METHODS

We conducted a systematic review of articles published prior to March 2018 by searching OVID MEDLINE, PsycINFO, EMBASE, and the references of included studies. We included comparative studies (cohort, case-control, cross-sectional) that reported on cannabis use in persons <25 years of age (exposure) and symptoms of psychosis, depression, or anxiety (outcome). We narratively synthesized the studies according to design (cohort, etc.) and psychiatric outcome. We used the Newcastle-Ottawa Scale to assess risk of bias.

RESULTS

Of the 534 citations identified through the literature search, 23 met the eligibility criteria and were included in this review. With psychosis as the outcome, all except one study found that earlier cannabis use was generally associated with higher risks. With depression/anxiety as the outcome, 6 of the 11 included studies reported findings indicating that earlier use of cannabis was linked to higher symptom levels.

CONCLUSION

In persons <25 years old, greater cannabis use is associated with more psychological symptoms, especially among those with a predisposition or existing vulnerability to such outcomes (Oxford Centre for Evidence-Based Medicine level 3 or 4). Policy makers need to consider the adverse effects of cannabis use in youth when planning a public health approach to cannabis legalization.

Pattern-based formulation: clinical case 5

OBJECTIVE:

To demonstrate how the Pattern-based Formulation can be used to integrate biological, psychological and sociocultural factors in constructing the case formulation in a patient who developed schizophrenia and post-psychotic depression.

CONCLUSIONS:

Three new patterns are introduced and used to construct a comprehensive case formulation. This expands the suite of patterns in the pattern-based method of psychiatric case formulation, and further demonstrates its broad utility as an educational resource in psychiatry training.

Interactions Between Variation in Candidate Genes and Environmental Factors in the Etiology of Schizophrenia and Bipolar Disorder: a Systematic Review

Schizophrenia and bipolar disorder (BD) are complex and multidimensional disorders with high heritability rates. The contribution of genetic factors to the etiology of these disorders is increasingly being recognized as the action of multiple risk variants with small effect sizes, which might explain only a minor part of susceptibility. On the other site, numerous environmental factors have been found to play an important role in their causality. Therefore, in recent years, several studies focused on gene × environment interactions that are believed to bridge the gap between genetic underpinnings and environmental insults. In this article, we performed a systematic review of studies investigating gene × environment interactions in BD and schizophrenia spectrum phenotypes. In the majority of studies from this field, interacting effects of variation in genes encoding catechol-O-methyltransferase (COMT), brain-derived neurotrophic factor (BDNF), and FK506-binding protein 5 (FKBP5) have been explored. Almost consistently, these studies revealed that polymorphisms in COMT, BDNF, and FKBP5 genes might interact with early life stress and cannabis abuse or dependence, influencing various outcomes of schizophrenia spectrum disorders and BD. Other interactions still require further replication in larger clinical and non-clinical samples. In addition, future studies should address the direction of causality and potential mechanisms of the relationship between gene × environment interactions and various categories of outcomes in schizophrenia and BD.

A comparative study of socio-demographic and substance use correlates in early-onset psychosis

BACKGROUND

Comorbid substance use, particularly cannabis among adolescents with mental illness, is a major public health concern in developing countries with limited mental health resources. Better understanding of the association between cannabis use and other polysubstance use and early mental illness will provide for more targeted early interventions.

AIM

This aim of this study was to examine the socio-demographic profile and cannabis use characteristics among adolescents with first-episode early-onset psychosis (EOP) and compare with age-matched and gender-matched adolescents with first-episode non-psychotic mental illness (controls).

METHOD

Forty-five adolescents with first-episode EOP and 45 controls were assessed using a clinical interview, Positive and Negative Syndrome Scale and World Health Organization Alcohol, Smoking and Substance Involvement Screening test (ASSIST) for substance-related problems.

RESULTS

There were significant socio-demographic differences among the adolescents with EOP (73% Black, 64% from low family income, 44% from rural areas) compared with controls (24% Black, 53% from low family income, 2% from rural areas). Although there was no difference in lifetime cannabis use, EOP adolescents differed in motivation for cannabis use, had increased current cannabis use (38%, P = 0.01) and more frequent use (52%, P = 0.04) compared with controls (16% current and 18% frequent use). EOP adolescents reported more hazardous use with higher ASSIST mean cannabis-specific involvement scores (EOP 10,2; controls 2,3; P = 0.004).

CONCLUSION

The differences in socio-demographic variables may reflect the marked disparity in access to mental health care for rural Black youth. Psychotic youth may be more vulnerable to comorbid cannabis-related problems than other mentally ill adolescents. The study highlights the need for early introduction of substance use interventions among adolescents with mental illness.

The interaction between cannabis use and the Val158Met polymorphism of the COMT gene in psychosis: A transdiagnostic meta - analysis

BACKGROUND

Neither environmental nor genetic factors are sufficient to predict the transdiagnostic expression of psychosis. Therefore, analysis of gene-environment interactions may be productive.

OBJECTIVE

A meta-analysis was performed using papers investigating the interaction between cannabis use and catechol-O-methyl transferase (COMT) polymorphism Val158Met (COMTVal158Met).

DATA SOURCES

PubMed, Embase, PsychInfo.

STUDY ELIGIBILITY CRITERIA

All observational studies assessing the interaction between COMTVal158Met and cannabis with any psychosis or psychotic symptoms measure as an outcome.

STUDY APPRAISAL AND SYNTHESIS METHODS

A meta-analysis was performed using the Meta-analysis of Observational Studies in Epidemiology guidelines and forest plots were generated. Thirteen articles met the selection criteria: 7 clinical studies using a case-only design, 3 clinical studies with a dichotomous outcome, and 3 studies analysing a continuous outcome of psychotic symptoms below the threshold of psychotic disorder. The three study types were analysed separately. Validity of the included studies was assessed using "A Cochrane Risk of Bias Assessment Tool: for Non-Randomized Studies of Interventions".

RESULTS

For case-only studies, a significant interaction was found between cannabis use and COMTVal158Met, with an OR of 1.45 (95% Confidence Interval = 1.05-2.00; Met/Met as the risk genotype). However, there was no evidence for interaction in either the studies including dichotomous outcomes (B = -0.51, 95% Confidence Interval -1.72, 0.70) or the studies including continuous outcomes (B = -0.04 95% Confidence Interval -0.16-0.08).

LIMITATION

A substantial part of the included studies used the case-only design, which has lower validity and tends to overestimate true effects.

CONCLUSION

The interaction term between cannabis use and COMTVal158Met was only statistically significant in the case-only studies, but not in studies using other clinical or non-clinical psychosis outcomes. Future additional high quality studies might change current perspectives, yet currently evidence for the interaction remains unconvincing.

Investigation of the COMT Val158Met variant association with age of onset of psychosis, adjusting for cannabis use

OBJECTIVE

COMT rs4680 (Val158Met) genotype moderates the effect of cannabis on the age of onset of psychosis (AoP). We investigated the association between rs4680 and AoP, after adjusting for relevant covariates, in a Canadian Caucasian sample.

METHODS

One hundred and sixty-nine subjects with psychosis were recruited. AoP, defined as age of DSM-IV diagnosis was established using the Structured Clinical Interview for DSM-IV. Cannabis use data were collected using a self-report computerized questionnaire. DNA was extracted from saliva and genotyping of the COMT Val158Met polymorphism was done by SNaPshot and TaqMan assays. Kaplan-Meier analysis results are reported.

RESULTS

In those who had used cannabis before 20 years of age, rs4680 had a trend level effect on AoP (median AoP: Val/Val < Val/Met < Met/Met 19.37, 20.95, 21.24 years, respectively; log-rank test p = .051).

CONCLUSION

Our data are indicative of the need to further investigate the association between the COMT rs4680 variant and AoP in the context of adolescent cannabis use.

Cannabis use, COMT, BDNF and age at first-episode psychosis

Although an interaction between COMT Val158Met and BDNF Val66Met polymorphisms with cannabis use has been proposed with respect to the risk of psychosis emergence, findings remain inconclusive. The aim of the present study was to evaluate the different possible associations between these polymorphisms and early cannabis use and the age at the first episode of psychosis. The relationship between age at psychosis onset and COMT Val158Met and BDNF Val66Met polymorphisms with early cannabis use as well as those factors associated with early cannabis use were investigated. Among 260 Caucasian first-episode psychosis patients, early cannabis use and the presence of the met-allele from the BDNF Val66Met polymorphism were significantly associated with age at psychosis onset. Furthermore, early cannabis use was significantly associated with male gender in the logistic regression analysis. These findings provide evidence of the important role of early cannabis use and the Val66Met BDNF polymorphism on age at psychosis onset and they point out to sex-specific differences in cannabis use patterns.

Depression, marijuana use and early-onset marijuana use conferred unique effects on neural connectivity and cognition

OBJECTIVE

Marijuana (MJ) use is common. Research shows risks for psychiatric illnesses, including major depressive disorder (MDD) and cognitive deficits with MJ use, particularly early-onset use. We investigated cognitive function, functional connectivity, and genetic risk with MDD alone and combined with MJ use, and differences between early-vs. late-onset/non-MJ use in youth.

METHOD

A total of 74 youth in four groups were studied: healthy control, MDD, frequent MJ use and current/past MDD plus frequent MJ use. Psychiatric symptoms, cognitive performance and demographics were measured. Default mode network (DMN) brain connectivity was determined. Risk alleles in six genes of interest were evaluated.

RESULTS

DMN differences among groups in reward-processing and motor control regions were found; the effects of MJ use and MDD were distinct. Early-onset MJ use was associated with lower IQ and hyperconnectivity within areas of the DMN. Early-onset MJ use was associated with the BDNF risk allele.

CONCLUSIONS

Cognitive deficits linked with early-onset MJ use were present within several years after MJ use began and may result from, predispose to, or share a common cause with early-onset MJ use. The DMN was affected by MDD, MJ and their combination, as well as by early-onset MJ use. BDNF carrier state may predispose to early-onset MJ use.

Cannabis and development of dual diagnoses: A literature review

BACKGROUND

The use of cannabis has garnered more attention recently with ongoing efforts at marijuana legalization. The consequences of cannabis use are not clearly understood and remain a concern.

OBJECTIVES

To review the acute and persistent effects of cannabis use and associations with psychiatric disorders.

METHODS

Using Pubmed and PsychInfo, we conducted a narrative review of the literature on cannabis and psychiatric comorbidity using the keywords cannab*, marijuana, schizo*, psychosis, mood, depression, mania, bipolar, and anxiety.

RESULTS

There is substantial evidence of cannabis use leading to other illicit drug use and of an association between cannabis use and psychosis. A few reports suggest an association with bipolar disorder while the association with depression and anxiety disorders is mixed.

CONCLUSIONS

Whenever an association is observed between cannabis use and psychiatric disorders, the relationship is generally an adverse one. Age at the time of cannabis use appears to be an important factor with stronger associations observed between adolescent onset cannabis use and later onset of psychiatric disorders. Additional studies taking into account potential confounds (such as withdrawal symptoms, periods of abstinence, and other substance use) and moderators (such as age of initiation of cannabis use, the amount and frequency of drug use, prior history of childhood maltreatment, and gender) are needed to better understand the psychiatric consequences of cannabis use.

A Test-Replicate Approach to Candidate Gene Research on Addiction and Externalizing Disorders: A Collaboration Across Five Longitudinal Studies

This study presents results from a collaboration across five longitudinal studies seeking to test and replicate models of gene-environment interplay in the development of substance use and externalizing disorders (SUDs, EXT). We describe an overview of our conceptual models, plan for gene-environment interplay analyses, and present main effects results evaluating six candidate genes potentially relevant to SUDs and EXT (MAOA, 5-HTTLPR, COMT, DRD2, DAT1, and DRD4). All samples included rich longitudinal and phenotypic measurements from childhood/adolescence (ages 5-13) through early adulthood (ages 25-33); sample sizes ranged from 3487 in the test sample, to ~600-1000 in the replication samples. Phenotypes included lifetime symptom counts of SUDs (nicotine, alcohol and cannabis), adult antisocial behavior, and an aggregate externalizing disorder composite. Covariates included the first 10 ancestral principal components computed using all autosomal markers in subjects across the data sets, and age at the most recent assessment. Sex, ancestry, and exposure effects were thoroughly evaluated. After correcting for multiple testing, only one significant main effect was found in the test sample, but it was not replicated. Implications for subsequent gene-environment interplay analyses are discussed.

COMT Val(158)Met genotype and cannabis use in people with an At Risk Mental State for psychosis: Exploring Gene x Environment interactions

BACKGROUND

Epidemiological and retrospective studies suggest a cannabis x catechol-O-methyltransferase (COMT) Val(158)Met interaction effect on development of psychosis. The aim of this study was to examine this interaction and its association with severity of subclinical symptoms in people with an At Risk Mental State (ARMS) for psychosis.

METHODS

Severity of symptoms, cannabis use and genotype were assessed at baseline in 147 help-seeking young adults who met the ARMS criteria and agreed to participate in the Dutch Early Detection and Intervention (EDIE-NL) trial.

RESULTS

Cannabis use and COMT Val-allele showed an interaction effect in ARMS subjects. Subjects who were weekly cannabis users at some point prior to entering the study showed more severe positive symptoms. This effect increased if they were carriers of the COMT Val-allele and even more so if they were homozygous for the Val-allele.

CONCLUSIONS

Our results suggest that the COMT Val(158)Met polymorphism moderates the effect of regular cannabis use on severity of subclinical psychotic symptoms.

Schizophrenia: An Overview

Few changes were made to the diagnostic criteria for schizophrenia in DSM-5. Schizophrenia is a chronic mental illness with positive symptoms (delusions, hallucinations, disorganized speech and behavior), negative symptoms, and cognitive impairment. Discoveries in genetics, neuroimaging, and immune function continue to advance understanding of the etiologies for this elusive disease. The authors reviewed the current literature to give an overview. The topics include historical foundations, epidemiology, suicide risk, genomewide association studies, twin studies, neuroimaging, ventricular size, complement component 4 mediated synapse elimination, major histocompatibility complex markers, and associations seen in obstetrical complications, nutritional issues, prodromal and attenuated states, cannabis use, childhood trauma, immigration, and traumatic brain injury. Also reviewed are expressed emotions of caregivers and recidivism, conditions comorbid with obsessive-compulsive disorder, mood disorders, substance use, and finally some legal and ethical issues. These important developments in elucidating the disease mechanism will likely allow for the development of future novel treatment strategies.

At the Tip of an Iceberg: Prenatal Marijuana and Its Possible Relation to Neuropsychiatric Outcome in the Offspring

Endocannabinoids regulate brain development via modulating neural proliferation, migration, and the differentiation of lineage-committed cells. In the fetal nervous system, (endo)cannabinoid-sensing receptors and the enzymatic machinery of endocannabinoid metabolism exhibit a cellular distribution map different from that in the adult, implying distinct functions. Notably, cannabinoid receptors serve as molecular targets for the psychotropic plant-derived cannabis constituent Δ(9)-tetrahydrocannainol, as well as synthetic derivatives (designer drugs). Over 180 million people use cannabis for recreational or medical purposes globally. Recreational cannabis is recognized as a niche drug for adolescents and young adults. This review combines data from human and experimental studies to show that long-term and heavy cannabis use during pregnancy can impair brain maturation and predispose the offspring to neurodevelopmental disorders. By discussing the mechanisms of cannabinoid receptor-mediated signaling events at critical stages of fetal brain development, we organize histopathologic, biochemical, molecular, and behavioral findings into a logical hypothesis predicting neuronal vulnerability to and attenuated adaptation toward environmental challenges (stress, drug exposure, medication) in children affected by in utero cannabinoid exposure. Conversely, we suggest that endocannabinoid signaling can be an appealing druggable target to dampen neuronal activity if pre-existing pathologies associate with circuit hyperexcitability. Yet, we warn that the lack of critical data from longitudinal follow-up studies precludes valid conclusions on possible delayed and adverse side effects. Overall, our conclusion weighs in on the ongoing public debate on cannabis legalization, particularly in medical contexts.

Cannabis use and family history in adolescent first episode psychosis in Durban, South Africa

OBJECTIVES

To investigate the clinical correlates of cannabis use in adolescents with first episode psychosis (FEP).

METHODS

Inpatient psychiatric records provided demographic, lifetime cannabis use, family history of mental illness, and clinical data on 45 FEP adolescents, aged 12-18 years, admitted to a psychiatric unit in Durban, KwaZulu-Natal, South Africa, over a 2-year period.

RESULTS

Thirty-one (68.8%) of the 45 FEP adolescents reported a history of lifetime cannabis use. The age of FEP presentation and pre-diagnosis symptom duration was not significantly different in cannabis users versus non cannabis users. Of the 15/43 (34.8%) FEP patients with family history of mental illness, 10 had a history of cannabis use. The 26 (57.8%) schizophrenia spectrum disorder patients did not differ significantly from the 19 (42.2%) with other psychoses in terms of cannabis use and family history of mental illness. They were, however, significantly younger at age of presentation and had a significantly longer duration of pre-diagnosis symptoms.

CONCLUSIONS

These preliminary findings suggest a high prevalence of cannabis use in adolescents with FEP and highlight the public health concern of addressing substance abuse in the adolescent population.

Birth weight and obstetric complications determine age at onset in first episode of psychosis

BACKGROUND

Earlier age at onset of psychosis (AOP) has been associated with poor social adjustment and clinical outcome. Genetic and environmental factors such as obstetric complications, parental history of psychosis, advanced paternal age at time of birth, low birth weight and gestational age, and use of drugs have been described as bringing AOP forward. This study aims to evaluate the relationship between AOP and these factors in a sample of first episode of psychosis (FEP) patients.

METHODS

Clinical and sociodemographic data, age at FEP, age of parents at birth, parental history of psychosis, drug-use habits of the mother during pregnancy and of the patient before psychotic onset, and Lewis and Murray obstetric complication scale were obtained from 90 patients with FEP. Statistical analysis was performed by means of Pearson correlations, Chi-square tests, Student T-test analyses and a linear regression model using SPSS version 22.

RESULTS

Pre-eclampsia, need for incubator at birth, use of forceps, parental history of psychosis, and low birth weight were associated with an earlier AOP. Use of forceps and birth weight are the variables which best predict AOP in FEP. Stimulant drugs, which were mostly used together with cannabis and cocaine, were the only substances associated with an earlier AOP.

CONCLUSIONS

Our findings are consistent with previous study results and underline the role of the prenatal period in the development of psychosis and the importance of careful monitoring of pregnancy and delivery, especially in cases with familial history.

Alcohol and Relatively Pure Cannabis Use, but Not Schizotypy, are Associated with Cognitive Attenuations

Elevated schizotypy relates to similar cognitive attenuations as seen in psychosis and cannabis/polydrug use. Also, in schizotypal populations cannabis and polydrug (including licit drug) use are enhanced. These cognitive attenuations may therefore either be a behavioral marker of psychotic (-like) symptoms or the consequence of enhanced drug use in schizotypal populations. To elucidate this, we investigated the link between cognitive attenuation and cannabis use in largely pure cannabis users (35) and non-using controls (48), accounting for the potential additional influence of both schizotypy and licit drug use (alcohol, nicotine). Cognitive attenuations commonly seen in psychosis were associated with cannabis and alcohol use, but not schizotypy. Future studies should therefore consider (i) non-excessive licit substance use (e.g., alcohol) in studies investigating the effect of cannabis use on cognition and (ii) both enhanced illicit and licit substance use in studies investigating cognition in schizotypal populations.

Genetic dissection of the psychotomimetic effects of cannabinoid exposure

Cannabis use is an established risk factor for the development of schizophrenia and related psychotic disorders. Factors that may mediate susceptibility to the psychosis-inducing effects of cannabis include the age at onset of first cannabis use, genetic predisposition, as well as interaction with other environmental risk variables. Clinical and preclinical genetic studies provide increasing evidence that, in particular, genes encoding proteins implicated in dopamine signalling are implicated in the cannabis-psychosis association. In the present review, we focus on both human and animal studies which have focused on identifying the neuronal basis of these interactions. We conclude that further studies are required to provide greater mechanistic insight into the long-term and neurodevelopmental effects of cannabis use, with implications for improved understanding of the cannabis-psychosis relationship.

Modulation of brain structure by catechol-O-methyltransferase Val(158) Met polymorphism in chronic cannabis users

Neuroimaging studies have shown that chronic consumption of cannabis may result in alterations in brain morphology. Recent work focusing on the relationship between brain structure and the catechol-O-methyltransferase (COMT) gene polymorphism suggests that functional COMT variants may affect brain volume in healthy individuals and in schizophrenia patients. We measured the influence of COMT genotype on the volume of four key regions: the prefrontal cortex, neostriatum (caudate-putamen), anterior cingulate cortex and hippocampus-amygdala complex, in chronic early-onset cannabis users and healthy control subjects. We selected 29 chronic cannabis users who began using cannabis before 16 years of age and matched them to 28 healthy volunteers in terms of age, educational level and IQ. Participants were male, Caucasians aged between 18 and 30 years. All were assessed by a structured psychiatric interview (PRISM) to exclude any lifetime Axis-I disorder according to Diagnostic and Statistical Manual for Mental Disorders-Fourth Edition. COMT genotyping was performed and structural magnetic resonance imaging data was analyzed by voxel-based morphometry. The results showed that the COMT polymorphism influenced the volume of the bilateral ventral caudate nucleus in both groups, but in an opposite direction: more copies of val allele led to lesser volume in chronic cannabis users and more volume in controls. The opposite pattern was found in left amygdala. There were no effects of COMT genotype on volumes of the whole brain or the other selected regions. Our findings support recent reports of neuroanatomical changes associated with cannabis use and, for the first time, reveal that these changes may be influenced by the COMT genotype.

Impact of Cannabis Use on the Development of Psychotic Disorders

The link between cannabis use and psychosis comprises three distinct relationships: acute psychosis associated with cannabis intoxication, acute psychosis that lasts beyond the period of acute intoxication, and persistent psychosis not time-locked to exposure. Experimental studies reveal that cannabis, tetrahydrocannabinol (THC) and synthetic cannabinoids reliably produce transient positive, negative, and cognitive symptoms in healthy volunteers. Case-studies indicate that cannabinoids can induce acute psychosis which lasts beyond the period of acute intoxication but resolves within a month. Exposure to cannabis in adolescence is associated with a risk for later psychotic disorder in adulthood; this association is consistent, temporally related, shows a dose-response, and is biologically plausible. However, cannabis is neither necessary nor sufficient to cause a persistent psychotic disorder. More likely it is a component cause that interacts with other factors to result in psychosis. The link between cannabis and psychosis is moderated by age at onset of cannabis use, childhood abuse and genetic vulnerability. While more research is needed to better characterize the relationship between cannabinoid use and the onset and persistence of psychosis, clinicians should be mindful of the potential risk of psychosis especially in vulnerable populations, including adolescents and those with a psychosis diathesis.

Gene-sex interactions in schizophrenia: focus on dopamine neurotransmission

Schizophrenia is a severe mental disorder, with a highly complex and heterogenous clinical presentation. Our current perspectives posit that the pathogenic mechanisms of this illness lie in complex arrays of gene × environment interactions. Furthermore, several findings indicate that males have a higher susceptibility for schizophrenia, with earlier age of onset and overall poorer clinical prognosis. Based on these premises, several authors have recently begun exploring the possibility that the greater schizophrenia vulnerability in males may reflect specific gene × sex (G×S) interactions. Our knowledge on such G×S interactions in schizophrenia is still rudimentary; nevertheless, the bulk of preclinical evidence suggests that the molecular mechanisms for such interactions are likely contributed by the neurobiological effects of sex steroids on dopamine (DA) neurotransmission. Accordingly, several recent studies suggest a gender-specific association of certain DAergic genes with schizophrenia. These G×S interactions have been particularly documented for catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO), the main enzymes catalyzing DA metabolism. In the present review, we will outline the current evidence on the interactions of DA-related genes and sex-related factors, and discuss the potential molecular substrates that may mediate their cooperative actions in schizophrenia pathogenesis.

Cannabis controversies: how genetics can inform the study of comorbidity

AIMS

To review three key and controversial comorbidities of cannabis use-other illicit drug use, psychosis and depression, as well as suicide, from a genetically informed perspective.

DESIGN

Selective review.

RESULTS

Genetic factors play a critical role in the association between cannabis use, particularly early-onset use and use of other illicit drugs, psychosis and depression, as well as suicide, albeit via differing mechanisms. For other illicit drugs, while there is strong evidence for shared genetic influences, residual association that is attributable to causal or person-specific environmental factors cannot be ruled out. For depression, common genetic influences are solely responsible for the association with cannabis use but for suicidal attempt, evidence for person-specific factors persists. Finally, even though rates of cannabis use are inordinately high in those with psychotic disorders, there is no evidence of shared genetic etiologies underlying this comorbidity. Instead, there is limited evidence that adolescent cannabis use might moderate the extent to which diathesis influences psychosis.

CONCLUSIONS

Overlapping genetic influences underlie the association between early-onset cannabis use and other illicit drug use as well as depression and suicide. For psychosis, mechanisms other than shared genetic influences might be at play.

Epidemiological, neurobiological, and genetic clues to the mechanisms linking cannabis use to risk for nonaffective psychosis

Epidemiological studies have shown that the association between cannabis and psychosis is robust and consistent across different samples, with compelling evidence for a dose-response relationship. Because longitudinal work indicates that cannabis use precedes psychotic symptoms, it seems reasonable to assume a causal relationship. However, more work is needed to address the possibility of gene-environment correlation (for example, genetic risk for psychosis causing onset of cannabis use). Moreover, knowledge about underlying biological mechanisms linking cannabis use and psychosis is still relatively limited. In order to understand how cannabis use may lead to an increased risk for psychosis, in the present article we (a) review the epidemiological, neurobiological, and genetic evidence linking cannabinoids and psychosis, (b) assess the quality of the evidence, and finally (c) try to integrate the most robust findings into a neurodevelopmental model of cannabis-induced psychosis and identify the gaps in knowledge that are in need of further investigation.

Gone to Pot - A Review of the Association between Cannabis and Psychosis

Cannabis is the most commonly used illicit drug worldwide, with ~5 million daily users worldwide. Emerging evidence supports a number of associations between cannabis and psychosis/psychotic disorders, including schizophrenia. These associations-based on case-studies, surveys, epidemiological studies, and experimental studies indicate that cannabinoids can produce acute, transient effects; acute, persistent effects; and delayed, persistent effects that recapitulate the psychopathology and psychophysiology seen in schizophrenia. Acute exposure to both cannabis and synthetic cannabinoids (Spice/K2) can produce a full range of transient psychotomimetic symptoms, cognitive deficits, and psychophysiological abnormalities that bear a striking resemblance to symptoms of schizophrenia. In individuals with an established psychotic disorder, cannabinoids can exacerbate symptoms, trigger relapse, and have negative consequences on the course of the illness. Several factors appear to moderate these associations, including family history, genetic factors, history of childhood abuse, and the age at onset of cannabis use. Exposure to cannabinoids in adolescence confers a higher risk for psychosis outcomes in later life and the risk is dose-related. Individuals with polymorphisms of COMT and AKT1 genes may be at increased risk for psychotic disorders in association with cannabinoids, as are individuals with a family history of psychotic disorders or a history of childhood trauma. The relationship between cannabis and schizophrenia fulfills many but not all of the standard criteria for causality, including temporality, biological gradient, biological plausibility, experimental evidence, consistency, and coherence. At the present time, the evidence indicates that cannabis may be a component cause in the emergence of psychosis, and this warrants serious consideration from the point of view of public health policy.

Psychosis-inducing effects of cannabis are related to both childhood abuse and COMT genotypes

OBJECTIVE

To test whether the association between childhood abuse, cannabis use and psychotic experiences (PEs) was moderated by the COMT (catechol-O-methyltransferase) gene.

METHOD

Psychotic experiences (PEs), childhood abuse, cannabis use and COMT Val158Met genotypes were assessed in 533 individuals from the general population. Data were analysed hierarchically by means of multiple linear regression models.

RESULTS

Childhood abuse showed a significant main effect on both positive (β = 0.09; SE = 0.04; P = 0.047) and negative PEs (β = 0.11; SE = 0.05; P = 0.038). A significant three-way interaction effect was found among childhood abuse, cannabis use and the COMT gene on positive PEs (β = -0.30; SE = 0.11; P = 0.006). This result suggests that COMT genotypes and cannabis use only influenced PE scores among individuals exposed to childhood abuse. Furthermore, exposure to childhood abuse and cannabis use increased PE scores in Val carriers. However, in individuals exposed to childhood abuse but who did not use cannabis, PEs increased as a function of the Met allele copies of the COMT gene.

CONCLUSION

Cannabis use after exposure to childhood abuse may have opposite effects on the risk of PEs, depending on the COMT genotypes providing evidence for a qualitative interaction. Val carriers exposed to childhood abuse are vulnerable to the psychosis-inducing effects of cannabis.

Duration of untreated psychosis in adolescents: ethnic differences and clinical profiles

BACKGROUND

Duration of Untreated Psychosis (DUP) is an important measure associated with outcome of psychosis. This first study in the UK compared DUP between adolescent and adult-onset individuals and explored whether the adolescent-onset group showed variations in DUP that could be accounted for by sociodemographic and selected risk factors.

METHODS

This naturalistic cohort study included 940 new first-episode psychosis cases aged 14-35years (136 adolescent-onset versus 804 adult-onset psychotic individuals) referred to nine Early Intervention Services for Psychosis in London (2003-2009). Sociodemographic characteristics, age of onset, family history of mental illness, duration of untreated psychosis, suicidality and substance use information were collected at entry to the services.

RESULTS

Adolescents presented with significantly greater median DUP (179days) than adults (81days, p=0.005). Large differences in DUP were found amongst adolescent ethnic groups (median DUP: White: 454days; Black: 103days; Asian and mixed: 28.5days). In addition, younger age of onset and higher lifetime cannabis use were associated with longer treatment delay amongst adolescents.

CONCLUSIONS

This study of DUP in adolescent-onset psychosis found it to be approximately twice the length of DUP amongst adults. For the adolescent White sub-group, DUP was far greater than the UK Department of Health target (<3months). Both the high rates of lifetime cannabis use and the lower age of onset might explain the long DUP in this ethnic group. Physicians need to be particularly vigilant about identifying and managing early psychosis in adolescents.

Cannabis Use during Adolescent Development: Susceptibility to Psychiatric Illness

Cannabis use is increasingly pervasive among adolescents today, even more common than cigarette smoking. The evolving policy surrounding the legalization of cannabis reaffirms the need to understand the relationship between cannabis exposure early in life and psychiatric illnesses. cannabis contains psychoactive components, notably Δ(9)-tetrahydrocannabinol (THC), that interfere with the brain's endogenous endocannabinoid system, which is critically involved in both pre- and post-natal neurodevelopment. Consequently, THC and related compounds could potentially usurp normal adolescent neurodevelopment, shifting the brain's developmental trajectory toward a disease-vulnerable state, predisposing early cannabis users to motivational, affective, and psychotic disorders. Numerous human studies, including prospective longitudinal studies, demonstrate that early cannabis use is associated with major depressive disorder and drug addiction. A strong association between schizophrenia and cannabis use is also apparent, especially when considering genetic factors that interact with this environmental exposure. These human studies set a foundation for carefully controlled animal studies which demonstrate similar patterns following early cannabinoid exposure. Given the vulnerable nature of adolescent neurodevelopment and the persistent changes that follow early cannabis exposure, the experimental findings outlined should be carefully considered by policymakers. In order to fully address the growing issues of psychiatric illnesses and to ensure a healthy future, measures should be taken to reduce cannabis use among teens.

The effect of childhood maltreatment and cannabis use on adult psychotic symptoms is modified by the COMT Val¹⁵⁸Met polymorphism

BACKGROUND

Cannabis use and childhood maltreatment are independent risk factors for the development of psychotic symptoms. These factors have been found to interact in some but not all studies. One of the reasons may be that childhood maltreatment and cannabis primarily induce psychotic symptoms in genetically susceptible individuals. In this context, an extensively studied psychosis vulnerability gene is catechol-methyl-transferase (COMT). Therefore, we aimed to examine whether the COMT Val(158)Met polymorphism (rs4680) moderates the interaction between childhood maltreatment and cannabis use on psychotic symptoms in the general population.

METHOD

The discovery sample consisted of 918 individuals from a cross-sectional study. For replication we used an independent sample of 339 individuals from the general population.

RESULTS

A significant three-way interaction was found between childhood maltreatment, cannabis use, and the COMT genotype (rs4680) in the discovery sample (P=0.006). Val-homozygous individuals displayed increased psychotic experiences after exposure to both cannabis use and childhood maltreatment compared to Met-heterozygous and Met-homozygous individuals. Supportive evidence was found in the replication sample with similar effect and direction even though the results did not reach statistical significance (P=0.25).

CONCLUSIONS

These findings suggest that a functional polymorphism in the COMT gene may moderate the interaction between childhood maltreatment and cannabis use on psychotic experiences in the general population. In conclusion, the COMT Val(158)Met polymorphism may constitute a genetic risk factor for psychotic symptoms in the context of combined exposure to childhood maltreatment and cannabis use.

Improving the reliability and reporting of genetic association studies

Genetic association studies, in particular candidate gene studies, have a long history of initially promising findings which subsequently produce a confusing mixture of replications, partial replications and non-replications. Drug and Alcohol Dependence is receiving an increasing number of submissions of genetic association studies. Here we discuss the journal's approach to considering such papers, in order to encourage credible and balanced reports which will contribute positively to the field. Recently, the STrengthening the REporting of Genetic Association studies (STREGA) initiative has provided guidelines which serve to enhance transparency. We strongly encourage authors considering submitting a genetic association study to the journal to follow these guidelines.

Age at initiation of cannabis use predicts age at onset of psychosis: the 7- to 8-year trend

We investigated the existence of a temporal association between age at initiation of cannabis use and age at onset of psychotic illness in 997 participants from the 2010 Survey of High Impact Psychosis (SHIP) in Australia. We tested for group differences in age at onset of psychotic illness and in the duration of premorbid exposure to cannabis (DPEC). Analyses were repeated in subgroups of participants with a schizophrenia-spectrum disorder (SSD), a diagnosis of lifetime cannabis dependence (LCD), and a comorbid SSD/LCD diagnosis. The association between age at initiation of cannabis use and age at onset of psychotic illness was linear and significant, F(11, 984) = 13.77, P < .001, even after adjusting for confounders. The effect of age at initiation of cannabis use on DPEC was not significant (mean duration of 7.8 years), and this effect was similar in participants with a SSD, LCD, and comorbid SSD/ LCD diagnosis although a shift toward shorter premorbid exposure to cannabis was noted in the SSD/LCD subgroup (mean duration of 7.19 years for SSD/LCD). A temporal direct relationship between age at initiation of cannabis use and age at onset of psychotic illness was detected with a premorbid exposure to cannabis trend of 7-8 years, modifiable by higher severity of premorbid cannabis use and a diagnosis of SSD. Cannabis may exert a cumulative toxic effect on individuals on the pathway to developing psychosis, the manifestation of which is delayed for approximately 7-8 years, regardless of age at which cannabis use was initiated.

Age at onset of non-affective psychosis in relation to cannabis use, other drug use and gender

BACKGROUND

Cannabis use is associated with an earlier age at onset of psychotic illness. The aim of the present study was to examine whether this association is confounded by gender or other substance use in a large cohort of patients with a non-affective psychotic disorder.

METHOD

In 785 patients with a non-affective psychotic disorder, regression analysis was used to investigate the independent effects of gender, cannabis use and other drug use on age at onset of first psychosis.

RESULTS

Age at onset was 1.8 years earlier in cannabis users compared to non-users, controlling for gender and other possible confounders. Use of other drugs did not have an additional effect on age at onset when cannabis use was taken into account. In 63.5% of cannabis-using patients, age at most intense cannabis use preceded the age at onset of first psychosis. In males, the mean age at onset was 1.3 years lower than in females, controlling for cannabis use and other confounders.

CONCLUSIONS

Cannabis use and gender are independently associated with an earlier onset of psychotic illness. Our findings also suggest that cannabis use may precipitate psychosis. More research is needed to clarify the neurobiological factors that make people vulnerable to this precipitating effect of cannabis.

Association between age at onset of psychosis and age at onset of cannabis use in non-affective psychosis

INTRODUCTION

Several studies have associated cannabis use with the development of schizophrenia. However, it has been difficult to disentangle the effects of cannabis from that of other illicit drugs, as previous studies have not evaluated pure cannabis users. To test whether the onset of cannabis use had an effect on the initiation of psychosis, we examined the time relationship between onset of use and onset of psychosis, restricting our analysis to a cohort of individuals who only used cannabis and no other street drugs.

METHODS

Fifty-seven subjects with non-affective psychoses who used cannabis prior to developing a psychosis were interviewed using the Diagnostic Interview for Genetic Studies (DIGS). The Family Interview for Genetic Studies (FIGS) was also used to interview a family informant about psychiatric illness in the patient and the entire family. Multiple linear regression techniques were used to estimate the association between variables.

RESULTS

After adjusting for potential confounding factors such as sex, age, lifetime diagnosis of alcohol abuse or dependence, and family history of schizophrenia, the age at onset of cannabis was significantly associated with age at onset of psychosis (β=0.4, 95% CI=0.1-0.7, p=0.004) and age at first hospitalization (β=0.4, 95% CI=0.1-0.8, p=0.008). The mean time between beginning to use cannabis and onset of psychosis was 7.0±4.3. Age at onset of alcohol use was not associated with age at onset of psychosis or age at first hospitalization.

CONCLUSION

Age at onset of cannabis is directly associated with age at onset of psychosis and age at first hospitalization. These associations remain significant after adjusting for potential confounding factors and are consistent with the hypothesis that cannabis could cause or precipitate the onset of psychosis after a prolonged period of time.

The association between social phobia, social anxiety cognitions and paranoid symptoms

OBJECTIVE

Previous research suggests high levels of comorbidity between social phobia and paranoid symptoms, although the nature of this association remains unclear.

METHOD

Data were derived from the Early Developmental Stages of Psychopathology study, a 10-year longitudinal study in a representative German community sample of 3021 participants aged 14-24 years at baseline. The Munich-Composite International Diagnostic Interview was used to assess social phobia and paranoid symptoms, along with data on social phobia features. Cross-sectional and longitudinal analyses were conducted. Differential associations with environmental risk factors and temperamental traits were investigated.

RESULTS

Lifetime social phobia and paranoid symptoms were associated with each other cross-sectionally (OR = 1.80, 95% CI = 1.31-2.47). Lifetime paranoid symptoms were associated specifically with social anxiety cognitions. Lifetime cognitions of negative evaluation predicted later onset of paranoid symptoms, whereas onset of social phobia was predicted by cognitions of loss of control and fear/avoidance of social situations. Lifetime social phobia and paranoid symptoms shared temperamental traits of behavioural inhibition, but differed in environmental risks.

CONCLUSIONS

The present study showed that paranoid symptoms and social phobia share similarities in cognitive profile and inhibited temperament. Avoidance appears to be important in the development of social phobia, whereas cannabis use and traumatic experiences may drive paranoid thinking in vulnerable individuals.