Linking substance use with symptoms of subclinical psychosis in a community cohort over 30 years

Risk-thresholds for the association between frequency of cannabis use and the development of psychosis: a systematic review and meta-analysis

BACKGROUND

Epidemiological studies show a dose-response association between cannabis use and the risk of psychosis. This review aimed to determine whether there are identifiable risk-thresholds between the frequency of cannabis use and psychosis development.

METHODS

Systematic search of Embase, MEDLINE, PsycINFO, CINAHL, and Web of Science for relevant studies (1 January 2010-26 April 2021). Case-control or cohort studies that investigated the relationship between cannabis use and the risk of psychosis development that reported effect estimates [odds ratios (OR), hazard ratios (HR), risk ratios (RR)] or the raw data to calculate them, with information on the frequency of cannabis consumption were included. Effect estimates were extracted from individual studies and converted to RR. Two-stage dose-response multivariable meta-analytic models were utilized and sensitivity analyses conducted. The Newcastle Ottawa Scale was used to assess the risk of bias of included studies.

RESULTS

Ten original (three cohorts, seven case-control) studies were included, including 7390 participants with an age range of 12-65 years. Random-effect model meta-analyses showed a significant log-linear dose-response association between cannabis use frequency and psychosis development. A restricted cubic-splines model provided the best fit for the data, with the risk of psychosis significantly increasing for weekly or more frequent cannabis use [RR = 1.01, 95% confidence interval (CI) 0.93-1.11 yearly; RR = 1.10, 95% CI 0.97-1.25 monthly; RR = 1.35, 95% CI 1.19-1.52 weekly; RR = 1.76, 95% CI 1.47-2.12 daily].

CONCLUSION

Individuals using cannabis frequently are at increased risk of psychosis, with no significant risk associated with less frequent use. Public health prevention messages should convey these risk-thresholds, which should be refined through further work.

Cannabinoids, reward processing, and psychosis

BACKGROUND

Evidence suggests that an overlap exists between the neurobiology of psychotic disorders and the effects of cannabinoids on neurocognitive and neurochemical substrates involved in reward processing.

AIMS

We investigate whether the psychotomimetic effects of delta-9-tetrahydrocannabinol (THC) and the antipsychotic potential of cannabidiol (CBD) are underpinned by their effects on the reward system and dopamine.

METHODS

This narrative review focuses on the overlap between altered dopamine signalling and reward processing induced by cannabinoids, pre-clinically and in humans. A systematic search was conducted of acute cannabinoid drug-challenge studies using neuroimaging in healthy subjects and those with psychosis RESULTS: There is evidence of increased striatal presynaptic dopamine synthesis and release in psychosis, as well as abnormal engagement of the striatum during reward processing. Although, acute THC challenges have elicited a modest effect on striatal dopamine, cannabis users generally indicate impaired presynaptic dopaminergic function. Functional MRI studies have identified that a single dose of THC may modulate regions involved in reward and salience processing such as the striatum, midbrain, insular, and anterior cingulate, with some effects correlating with the severity of THC-induced psychotic symptoms. CBD may modulate brain regions involved in reward/salience processing in an opposite direction to that of THC.

CONCLUSIONS

There is evidence to suggest modulation of reward processing and its neural substrates by THC and CBD. Whether such effects underlie the psychotomimetic/antipsychotic effects of these cannabinoids remains unclear. Future research should address these unanswered questions to understand the relationship between endocannabinoid dysfunction, reward processing abnormalities, and psychosis.

Adolescent cannabis use and later development of schizophrenia: An updated systematic review of longitudinal studies

BACKGROUND

The study aimed to review recent literature not included in previous reviews and ascertain the correlation between early marijuana use among adolescents, between 12 and 18 years of age, and the development of schizophrenia in early adulthood. A further aim was to determine if the frequency of use of marijuana demonstrated any significant effect on the risk of developing schizophrenia in early adulthood.

METHODS

Five hundred and ninety-one studies were examined; six longitudinal cohort studies were analyzed using a series of nonparametric tests and meta-analysis.

RESULTS

Nonparametric tests, Friedman tests, and Wilcoxon signed tests showed a highly statistically significant difference in odds ratios for schizophrenia between both high- and low-cannabis users and no-cannabis users.

CONCLUSION

Both high- and low-frequency marijuana usage were associated with a significantly increased risk of schizophrenia. The frequency of use among high- and low-frequency users is similar in both, demonstrating statistically significant increased risk in developing schizophrenia.

The Behavioral Sequelae of Cannabis Use in Healthy People: A Systematic Review

Background: Cannabis is known to have a broad range of effects on behavior, including experiencing a "high" and tranquility/relaxation. However, there are several adverse behavioral sequalae that can arise from cannabis use, depending on frequency of use, potency (e.g., THC content), age of onset, and cumulative exposure. This systematic review examined evidence for cannabis-related adverse behavioral sequalae in otherwise healthy human subjects. Methods: Following PRISMA guidelines, we conducted a systematic review of cross-sectional and longitudinal studies from 1990 to 2020 that identified cannabis-related adverse behavioral outcomes in subjects without psychiatric and medical co-morbidities from PubMed and PsychInfo searches. Key search terms included "cannabis" OR "tetrahydrocannabinol" OR "cannabidiol" OR "marijuana" AND "anxiety" OR "depression" OR "psychosis" OR "schizophrenia" "OR "IQ" OR "memory" OR "attention" OR "impulsivity" OR "cognition" OR "education" OR "occupation". Results: Our search detected a total of 2,870 studies, from which we extracted 124 relevant studies from the literature on cannabis effects in the non-clinical population. Effects of cannabis on several behavioral sequelae including cognition, motivation, impulsivity, mood, anxiety, psychosis intelligence, and psychosocial functioning were identified. The preponderance of the evidence suggests that frequency of cannabis use, THC (but not CBD) content, age of onset, and cumulative cannabis exposure can all contribute to these adverse outcomes in individuals without a pre-existing medical condition or psychiatric disorder. The strongest evidence for the negative effects of cannabis are for psychosis and psychosocial functioning. Conclusions: Although more research is needed to determine risk factors for development of adverse behavioral sequelae of cannabis use, these findings underline the importance of understanding vulnerability to the adverse effects of cannabis, which has implications for prevention and treatment of problematic cannabis use.

Cannabis use during adolescence and the occurrence of depression, suicidality and anxiety disorder across adulthood: Findings from a longitudinal cohort study over 30 years

OBJECTIVE

To examine the association between cannabis use in adolescence and the occurrence of depression, suicidality and anxiety disorders during adulthood.

METHODS

A stratified population-based cohort of young adults (n = 591) from Zurich, Switzerland, was retrospectively assessed at age 19/20 for cannabis use in adolescence. The occurrence of depression, suicidality and anxiety disorders was repeatedly assessed via semi-structured clinical interviews at the ages of 20/21, 22/23, 27/28, 29/30, 34/35, 40/41, and 49/50. Associations were controlled for various covariates, including socio-economic deprivation in adolescence as well as repeated time-varying measures of substance abuse during adulthood.

RESULTS

About a quarter (24%) reported cannabis use during adolescence; 11% started at age 15/16 or younger and 13% between the ages of 16/17 and 19/20. In the adjusted multivariable model, cannabis use during adolescence was associated with adult depression (aOR = 1.70, 95%-CI = 1.24-2.32) and suicidality (aOR = 1.65, 95%-CI = 1.11-2.47), but not anxiety disorders (aOR = 1.10, 95%-CI = 0.82-1.48). First use at age 15/16 and younger (as against first use between age 16/17 and 19/20 and no use) and frequent use in adolescence (as against less frequent use and no use) were associated with a higher risk of depression in adult life.

CONCLUSIONS

In this longitudinal cohort study over 30-years, cannabis use during adolescence was associated with depression and suicidality in adult life. Young age at first use and high frequency of use in adolescence may particularly increase the risk of depression in adulthood. All associations were independent of cannabis abuse and other substance abuse during adulthood.

Unraveling the Intoxicating and Therapeutic Effects of Cannabis Ingredients on Psychosis and Cognition

Research evidence suggests a dose–response relationship for the association between cannabis use and risk of psychosis. Such relationship seems to reflect an increased risk of psychosis not only as a function of frequent cannabis use, but also of high-potency cannabis use in terms of concentration of Δ-9-tetrahydrocannabinol (Δ9-THC), its main psychoactive component. This finding would be in line with the evidence that Δ9-THC administration induces transient psychosis-like symptoms in otherwise healthy individuals. Conversely, low-potency varieties would be less harmful because of their lower amount of Δ9-THC and potential compresence of another cannabinoid, cannabidiol (CBD), which seems to mitigate Δ9-THC detrimental effects. A growing body of studies begins to suggest that CBD may have not only protective effects against the psychotomimetic effects of Δ9-THC but even therapeutic properties on its own, opening new prospects for the treatment of psychosis. Despite being more limited, evidence of the effects of cannabis on cognition seems to come to similar conclusions, with increasing Δ9-THC exposure being responsible for the cognitive impairments attributed to recreational cannabis use while CBD preventing such effects and, when administered alone, enhancing cognition. Molecular evidence indicates that Δ9-THC and CBD may interact with cannabinoid receptors with almost opposite mechanisms, with Δ9-THC being a partial agonist and CBD an inverse agonist/antagonist. With the help of imaging techniques, pharmacological studies in vivo have been able to show opposite effects of Δ9-THC and CBD also on brain function. Altogether, they may account for the intoxicating and therapeutic effects of cannabis on psychosis and cognition.

Lifetime and 12-month prevalence rates of sub-clinical psychosis symptoms in a community cohort of 50-year-old individuals

Background:

Estimation of prevalence rates of sub-clinical psychosis symptoms can vary considerably depending on the methodology used. Furthermore, discussions are ongoing how prevalence rates may differ across various syndromes.

Method:

We analyzed data from the prospective Zurich Study, assessing sub-clinical psychosis with a semi-structured clinical interview in a community cohort of 50 years old individuals. The higher-order factors of psychosis symptoms were analyzed with confirmatory factor analysis to validate the a priori specified symptom-structure. Further associations were examined with contingency tables and logistic regressions.

Results:

The confirmatory factor analysis was consistent with a structure with four higher-order syndromes. Those different syndromes were labeled “thought disorder” (lifetime prevalence = 10.6%), “ego disorder” (4.8%), “hallucination” (9.7%), and “schizotypy” (28.2%). A strong discrepancy was noted between the 12-month prevalence of any symptoms and those considered to be severe. Twelve-month prevalence rates of distressful syndromes ranged from 0.1% for hallucinations up to 6.6% for schizotypy. The most strongly interrelated syndromes were thought disorder and ego disorder (OR = 12.4).

Conclusion:

Our findings indicate a continuity of sub-clinical psychosis within the general population even though only a small proportion suffers from distressing symptoms. Our analyses showed that the syndromes identified here are similar to those found in full-blown schizophrenia, albeit in an attenuated form.

Dilemmas in the treatment of early-onset first-episode psychosis

Early-onset first-episode psychosis (EOP) is a severe mental disorder that can pose a number of challenges to clinicians, young people and their families. Its assessment and differentiation from other neurodevelopmental and mental health conditions may at times be difficult, its treatment may not always lead to optimal outcomes and can be associated with significant side effects, and its long-term course and prognosis seem to be less favourable compared with the adult-onset disorder. In this paper, we discuss some dilemmas associated with the evaluation and management of EOP and propose approaches that can be used in the clinical decision-making process. A detailed and well-informed assessment of psychotic symptoms and comorbidities, a systematic approach to treatment with minimum possible medication doses and close monitoring of its effectiveness and adverse effects, and multidimensional interventions taking into consideration risks and expectations associated with EOP, are paramount in the achievement of the most favourable outcomes for affected children and young people.

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

IMPORTANCE

There is concern about potentially causal effects of tobacco use on psychosis, but epidemiological studies have been less robust in attempts to minimize effects of confounding than studies of cannabis use have been.

OBJECTIVES

To examine the association of patterns of cigarette and cannabis use with preceding and subsequent psychotic experiences, and to compare effects of confounding across these patterns.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study used data from the Avon Longitudinal Study of Parents and Children, which initially consisted of 14 062 children. Data were collected periodically from September 6, 1990, with collection ongoing, and analyzed from August 8, 2016, through June 14, 2017. Cigarette and cannabis use data were summarized using longitudinal latent class analysis to identify longitudinal classes of substance use. Associations between classes and psychotic experiences at age 18 years were assessed.

EXPOSURES

Depending on the analysis model, exposures were longitudinal classes of substance use or psychotic experiences at age 12 years.

MAIN OUTCOMES AND MEASURES

Logistic regression was used to examine the associations between substance use longitudinal classes and subsequent onset of psychotic experiences.

RESULTS

Longitudinal classes were derived using 5300 participants (56.1% female) who had at least 3 measures of cigarette and cannabis use from ages 14 to 19 years. Prior to adjusting for a range of potential confounders, there was strong evdience that early-onset cigarette-only use (4.3%), early-onset cannabis use (3.2%), and late-onset cannabis use (11.9%) (but not later-onset cigarette-only use [14.8%]) latent classes were associated with increased psychotic experiences compared with nonusers (65.9%) (omnibus P < .001). After adjusting for confounders, the association for early-onset cigarette-only use attenuated substantially (unadjusted odds ratio [OR], 3.03; 95% CI, 1.13-8.14; adjusted OR, 1.78; 95% CI, 0.54-5.88), whereas those for early-onset cannabis use (adjusted OR, 3.70; 95% CI, 1.66-8.25) and late-onset cannabis use (adjusted OR, 2.97; 95% CI, 1.63-5.40) remained consistent.

CONCLUSIONS AND RELEVANCE

In this study, our findings indicate that while individuals who use cannabis or cigarettes during adolescence have an increased risk of subsequent psychotic experiences, epidemiological evidence is substantively more robust for cannabis use than it is for tobacco use.

Influence of depressive symptoms on distress related to positive psychotic-like experiences in women

The Community Assessment of Psychic Experiences (CAPE) is an effective instrument for detection of the presence of psychotic symptoms and associated distress in the general population. However, little research has studied distress associated with positive psychotic-like experiences (PLEs). Our aim is to study PLE-related distress using the CAPE. In this study we analysed factors associated with differences in PLE-related distress in a sample of 200 non-clinical participants recruited by snowball sampling. Presence of PLEs and related psychological distress was measured using the CAPE questionnaire. The influence of age, gender, educational level and drug use was studied. In univariate analysis we found that gender and CAPE positive, depressive and negative scores, were associated with CAPE positive distress. Using multiple linear regression, we found that only the effect of gender, and the interaction between frequency of depression and gender, remained statistically significant. In our sample interaction between gender and depressive symptoms is a determining factor in distress associated with positive PLEs. The results of this study may be useful for the implementation of prevention programs.

Cannabis and psychosis: the impact of polydrug use

Purpose

While research has consistently identified an association between cannabis use and psychosis, few studies have examined this relationship in a polydrug context (i.e. combining cannabis with other illicit substances). The paper aims to discuss this issue.

Design/methodology/approach

The present study sought to examine the association between recreational drug use (cannabis only vs polydrug) and psychotic disorders. Analysis was conducted on a large, representative survey of young Danish people aged 24 (n=4,718). Participants completed self-report measures of lifetime drug use and this information was linked to the Danish psychiatric registry system.

Findings

Multivariate binary logistic regression analysis was used to examine the association between drug use (no drug use, cannabis only, cannabis and other drug) and ICD-10 psychotic disorders, while controlling for gender and parental history of psychosis. Compared with no drug use, the use of cannabis only did not increase the risk of psychosis while the odds ratio for cannabis and other drug were statistically significant.

Research limitations/implications

Psychosis risk may be associated with the cumulative effect of polydrug use.

Practical implications

Cannabis use may be a proxy for other drug use in research studies.

Originality/value

This study is innovative as it uses linked self-report and administrative data for a large sample. Administrative data were used to as an objective mental health status indicator.

Differences in the Rates of Drug Polyconsumption and Psychiatric Comorbidity among Patients with Cocaine Use Disorders According to the Mental Health Service

Cocaine continues to be a worldwide public health concern in Europe. To improve prognosis and intervention, it is necessary to understand the characteristics of the patients who depend on the services where they receive care. The objective is to analyze the differences among patients who use cocaine and between ambulatory and residential resources to better adapt treatment. This is a descriptive, observational study of two populations of cocaine users in treatment: the ambulatory therapeutic community (ATC) and the therapeutic community (TC). The PRISM diagnostic interview was used for both groups. An analysis of both populations indicates a high prevalence of cocaine, heroin, cannabis, sedative, psychostimulant, and hallucinogen use disorders in the TC population compared to the ATC. In alcohol use disorder, differences between both mental health services were not observed. The degree of severity of cocaine use disorders (CUD) is greater in the TC population. The prevalence of psychiatric comorbidity is not statistically significant between the two populations, except for primary psychotic disorders, which are more prevalent in the TC population. This difference in the prevalence of psychotic disorders may be related to the high prevalence of cannabis use disorders in TC patients. Differences in the prevalence of substance use disorders, severity of CUD, and psychiatric comorbidity may limit the efficiency of mental health services involved in substance use disorder therapeutics. These results suggest the need for careful and extensive phenotyping of patients to improve intervention and prognosis in a clinical resource-dependent manner.

Poverty, low education, and the expression of psychotic-like experiences in the general population of São Paulo, Brazil

The aim of our study was to assess psychotic-like experiences in the general population aged 18-30 years old of the city of São Paulo, Brazil. A household survey was conducted with 1950 young-adults randomly drawn from the city's general population. The validated 92-item Portuguese version of the Prodromal Questionnaire (PQ) was used for face-to-face interviews. Latent class analysis was conducted. Mean age was of 24 years; 51.1% of the sample was of women. Mean total score on the PQ was 22.06 (SD=17.16). Considering a suggested cut-off of 14 in the positive subscale, 30.8% of individuals were above the threshold for ultra-high risk for psychosis detection. Latent class analysis resulted in a three classes clusterization. Class 1 (20%; n=390) had the highest overall PQ scores (mean=49.31,SD=10.783), class 2 (43%; n=835) had intermediate scores (mean=23.37,SD=6.56), and class 3 (37%; n=721) had the lowest scores (mean=5.81,SD=3.74). Class 1 had significantly more individuals with less education and significantly more individuals with lower socioeconomic class. Poverty and low education might be associated with the psychotic expression in the general population, amplifying their actions on the psychosis gradient in developing countries. The psychosis continuum might be constituted by three distinct quantitatively different classes.

Cannabis-associated psychosis: Neural substrate and clinical impact

Prospective epidemiological studies have consistently demonstrated that cannabis use is associated with an increased subsequent risk of both psychotic symptoms and schizophrenia-like psychoses. Early onset of use, daily use of high-potency cannabis, and synthetic cannabinoids carry the greatest risk. The risk-increasing effects are not explained by shared genetic predisposition between schizophrenia and cannabis use. Experimental studies in healthy humans show that cannabis and its active ingredient, delta-9-tetrahydrocannabinol (THC), can produce transient, dose-dependent, psychotic symptoms, as well as an array of psychosis-relevant behavioral, cognitive and psychophysiological effects; the psychotogenic effects can be ameliorated by cannabidiol (CBD). Findings from structural imaging studies in cannabis users have been inconsistent but functional MRI studies have linked the psychotomimetic and cognitive effects of THC to activation in brain regions implicated in psychosis. Human PET studies have shown that acute administration of THC weakly releases dopamine in the striatum but that chronic users are characterised by low striatal dopamine. We are beginning to understand how cannabis use impacts on the endocannabinoid system but there is much still to learn about the biological mechanisms underlying how cannabis increases risk of psychosis. This article is part of the Special Issue entitled "A New Dawn in Cannabinoid Neurobiology".

Assessing causality in associations between cannabis use and schizophrenia risk: a two-sample Mendelian randomization study

BACKGROUND

Observational associations between cannabis and schizophrenia are well documented, but ascertaining causation is more challenging. We used Mendelian randomization (MR), utilizing publicly available data as a method for ascertaining causation from observational data.

METHOD

We performed bi-directional two-sample MR using summary-level genome-wide data from the International Cannabis Consortium (ICC) and the Psychiatric Genomics Consortium (PGC2). Single nucleotide polymorphisms (SNPs) associated with cannabis initiation (p < 10-5) and schizophrenia (p < 5 × 10-8) were combined using an inverse-variance-weighted fixed-effects approach. We also used height and education genome-wide association study data, representing negative and positive control analyses.

RESULTS

There was some evidence consistent with a causal effect of cannabis initiation on risk of schizophrenia [odds ratio (OR) 1.04 per doubling odds of cannabis initiation, 95% confidence interval (CI) 1.01-1.07, p = 0.019]. There was strong evidence consistent with a causal effect of schizophrenia risk on likelihood of cannabis initiation (OR 1.10 per doubling of the odds of schizophrenia, 95% CI 1.05-1.14, p = 2.64 × 10-5). Findings were as predicted for the negative control (height: OR 1.00, 95% CI 0.99-1.01, p = 0.90) but weaker than predicted for the positive control (years in education: OR 0.99, 95% CI 0.97-1.00, p = 0.066) analyses.

CONCLUSIONS

Our results provide some that cannabis initiation increases the risk of schizophrenia, although the size of the causal estimate is small. We find stronger evidence that schizophrenia risk predicts cannabis initiation, possibly as genetic instruments for schizophrenia are stronger than for cannabis initiation.

U-shaped curve of psychosis according to cannabis use: New evidence from a snowball sample

BACKGROUND

The aim of this study was to investigate the relationship between psychotic-like experiences (PLEs) assessed using the Community Assessment of Psychic Experience (CAPE) questionnaire and the pattern of cannabis use in a non-clinical sample collected by snowball sampling.

METHODS

Our sample was composed of 204 subjects, distributed into three groups by their cannabis use pattern: 68 were non-cannabis users, 40 were moderate cannabis users and 96 were daily cannabis users. We assessed the psychotic experiences in each group with the CAPE questionnaire; and then controlled for the effect of possible confounding factors like sex, age, social exclusion, age of onset of cannabis use, alcohol use and other drug use.

RESULTS

We found a significant quadratic association between the frequency of cannabis use and positive (β = -1.8; p = 0.004) and negative dimension scores (β = -1.2; p = 0.04). The first-rank and mania factors showed a significant quadratic association (p < 0.05), while the voices factor showed a trend (p = 0.07). Scores for the different groups tended to maintain a U-shape in their values for the different factors. When we adjusted for gender, age, social exclusion, age of onset of cannabis use, and use of alcohol and other drugs, only the first-rank experiences remained significant.

CONCLUSIONS

We found there was a U-shaped curve in the association between cannabis use and the positive and negative dimensions of the CAPE score. We also found this association in mania and first-rank experiences.

Traditional marijuana, high-potency cannabis and synthetic cannabinoids: increasing risk for psychosis

Epidemiological evidence demonstrates that cannabis use is associated with an increased risk of psychotic outcomes, and confirms a dose-response relationship between the level of use and the risk of later psychosis. High-potency cannabis and synthetic cannabinoids carry the greatest risk. Experimental administration of tetrahydrocannabinol, the active ingredient of cannabis, induces transient psychosis in normal subjects, but this effect can be ameliorated by co-administration of cannabidiol. This latter is a constituent of traditional hashish, but is largely absent from modern high-potency forms of cannabis. Argument continues over the extent to which genetic predisposition is correlated to, or interacts with, cannabis use, and what proportion of psychosis could be prevented by minimizing heavy use. As yet, there is not convincing evidence that cannabis use increases risk of other psychiatric disorders, but there are no such doubts concerning its detrimental effect on cognitive function. All of the negative aspects are magnified if use starts in early adolescence. Irrespective of whether use of cannabis is decriminalized or legalized, the evidence that it is a component cause of psychosis is now sufficient for public health messages outlining the risk, especially of regular use of high-potency cannabis and synthetic cannabinoids.

Association Between Cannabis and Psychosis: Epidemiologic Evidence

Associations between cannabis use and psychotic outcomes are consistently reported, but establishing causality from observational designs can be problematic. We review the evidence from longitudinal studies that have examined this relationship and discuss the epidemiologic evidence for and against interpreting the findings as causal. We also review the evidence identifying groups at particularly high risk of developing psychosis from using cannabis. Overall, evidence from epidemiologic studies provides strong enough evidence to warrant a public health message that cannabis use can increase the risk of psychotic disorders. However, further studies are required to determine the magnitude of this effect, to determine the effect of different strains of cannabis on risk, and to identify high-risk groups particularly susceptible to the effects of cannabis on psychosis. We also discuss complementary epidemiologic methods that can help address these questions.

Treated versus non-treated subjects with depression from a 30-year cohort study: prevalence and clinical covariates

The aim of this study was to determine prevalence rates of several components of depression (unipolar and bipolar major, minor, recurrent brief depression, and dysthymia) and to identify covariates of treatment. We analysed a representative population-based, long-term prospective cohort study from age 20 to 50. Across the seven semi-structured interviews, generalized estimating equations examined the associations between diagnoses and treatment status during the course. The results show that the mean annual treatment rate across 30 years in persons with MDE was 39.2%. The weighted treatment prevalence for any depressive disorder was 23.4% (15.7% for MDE, 4.3% for minor depressive disorders and 3.4% for non-diagnosed subjects). Persons were more likely to seek treatment as they grew older. Women with MDE had triple the treatment prevalence of men (23.8 vs. 7.4%). Variables of distress/suffering under depression (OR 1.36-1.52) and the number of diagnostic depressive symptoms (OR 1.47) were statistically significant predictors of treatment, as were episode duration (OR 2.21) and various variables assessing impairment due to depression (OR 4.65-8.02). In conclusion, only a minority of persons with depressive disorders seek professional treatment in the year of disorder onset. Women and subjects suffering from high levels of depressive symptoms, frequent episodes, long episode duration and consecutive high distress and impairment were more likely to seek treatment.

Abnormalities in neuroendocrine stress response in psychosis: the role of endocannabinoids

The aim of this article is to summarize current evidence regarding alterations in the neuroendocrine stress response system and endocannabinoid system and their relationship in psychotic disorders such as schizophrenia. Exposure to stress is linked to the development of a number of psychiatric disorders including psychosis. However, the precise role of stress in the development of psychosis and the possible mechanisms that might underlie this are not well understood. Recently the cannabinoid hypothesis of schizophrenia has emerged as a potential line of enquiry. Endocannabinoid levels are increased in patients with psychosis compared with healthy volunteers; furthermore, they increase in response to stress, which suggests another potential mechanism for how stress might be a causal factor in the development of psychosis. However, research regarding the links between stress and the endocannabinoid system is in its infancy. Evidence summarized here points to an alteration in the baseline tone and reactivity of the hypothalamic-pituitary-adrenal (HPA) axis as well as in various components of the endocannabinoid system in patients with psychosis. Moreover, the precise nature of the inter-relationship between these two systems is unclear in man, especially their biological relevance in the context of psychosis. Future studies need to simultaneously investigate HPA axis and endocannabinoid alterations both at baseline and following experimental perturbation in healthy individuals and those with psychosis to understand how they interact with each other in health and disease and obtain mechanistic insight as to their relevance to the pathophysiology of schizophrenia.

Trends in cannabis-related ambulance presentations from 2000 to 2013 in Melbourne, Australia

AIMS

The current burden of cannabis-related presentations to emergency health services is largely unknown. This paper presents data collected over a 13-year period in metropolitan Melbourne, Australia as part of the Ambo Project, a unique surveillance system that analyses and codes paramedic records for drug-related trends and harms.

METHODS

Cannabis-related ambulance attendances involving 15-59 year olds in metropolitan Melbourne were analysed retrospectively from 2000 to 2013 (n=10,531). Trends and attendance characteristics were compared among cannabis only (CO)-, cannabis and alcohol (CA)- and cannabis with polydrug use (CP)-related attendances. Changes in alcohol and drug involvements in cannabis-related attendances were explored.

RESULTS

Rates of cannabis-related ambulance attendances increased significantly over the study period. Increasing rate of attendances per 100,000 population per year changed from 0.6 (2000-2010) to 5.5 (2010-2013). This sharp change was driven by CO- and CP-related attendances (rate of CA-related attendance increased steadily). The highest increasing rate (15.6) was for CO-related attendances among 15-29 years old males (2010-2013). Crystal methamphetamine became the most common illicit co-intoxicant amongst cannabis presentations in 2013.

CONCLUSIONS

Relative to the total drug-related burden on ambulance services, cannabis-related presentations appear to be a small but significant and increasing problem. Significant changes in trends across other drug involvement and demographic subgroups suggest a possible shift in the cannabis using population and/or a change in using behaviours. Public health strategies should raise awareness of the increased risk posed by cannabis polydrug use and high attendance subpopulations should be determined.

Psychopathology in Substance Use Disorder Patients with and without Substance-Induced Psychosis

Background. Substance-induced psychotic disorder (SIPD) is a diagnosis constructed to distinguish substance-induced psychotic states from primary psychotic disorders. A number of studies have compared SIPD persons with primary psychotic patients, but there is little data on what differentiates substance use disorder (SUD) individuals with and without SIPD. Here, we compared psychopathology, sociodemographic variables, and substance use characteristics between SUD patients with and without SIPD. Methods. A retrospective chart review was conducted on newly admitted patients at a rehabilitation centre between 2007 and 2012. Results. Of the 379 patients included in the study, 5% were diagnosed with SIPD (n = 19) and 95% were diagnosed with SUDs without SIPD (n = 360). More SIPD patients reported using cannabis and psychostimulants, and fewer SIPD patients reported using alcohol than SUDs patients without SIPD. SIPD patients scored higher on the “schizophrenia nuclear symptoms” dimension of the SCL-90R psychoticism scale and exhibited more ClusterB personality traits than SUD patients without SIPD. Discussion. These data are consistent with previous studies suggesting that psychopathology, substance type, and sociodemographic variables play important role in the development of SIPD. More importantly, the results highlight the need for paying greater attention to the types of self-reported psychotic symptoms during the assessment of psychotomimetic effects associated with psychoactive substances.

The Swiss Cohort Study on Substance Use Risk Factors – Findings of two Waves

Abstract. Aim: To summarize published findings in peer-reviewed journals of the first two waves of the Swiss Cohort Study on Substance Use Risk Factors (C-SURF), a longitudinal study assessing risk and protective factors of 5,987 young men during the phase of emerging adulthood (20 years at baseline, followed-up 15 months later). Methods: Included were 33 studies published until November 2014 focusing on substance use. Results: Substance use in early adulthood is a prevalent and stable behavior. The 12-month prevalence of nonmedical use of prescription drugs (10.6 %) lies between that of cannabis (36.4 %) and other illicit drugs such as ecstasy (3.7 %) and cocaine (3.2 %). Although peer pressure in the form of misconduct is associated with increased substance use, other aspects such as peer involvement in social activities may have beneficial effects. Regular sport activities are associated with reduced substance use, with the exception of alcohol use. Young men are susceptible to structural conditions such as the price of alcohol beverages or the density of on-premise alcohol outlets. Particularly alcohol use in public settings such as bars, discos or in parks (compared with private settings such as the home) is associated with alcohol-related harm, including injuries or violence. Being a single parent versus nuclear family has no effect on alcohol use, but active parenting does. Besides parenting, religiousness is an important protective factor for both legal and illegal substance use. Merely informing young men about the risks of substance use may not be an effective preventive measure. At-risk users of licit and illicit substances are more health literate, e. g., for example, they seek out more information on the internet than non-at-risk-users or abstainers. Discussion: There are a number of risk and protective substance use factors, but their associations with substance use do not necessarily agree with those found outside Europe. In the United States, for example, heavy alcohol use in this age group commonly takes place in private settings, whereas in Switzerland it more often takes place in public settings. Other behaviors, such as the nonmedical use of prescription drugs, appear to be similar to those found overseas, which may show the need for targeted preventive actions. C-SURF findings point to the necessity of establishing European studies to identify factors for designing specific preventive actions.

Associations of cannabis and cigarette use with depression and anxiety at age 18: findings from the Avon Longitudinal Study of Parents and Children

Introduction

Substance use is associated with common mental health disorders, but the causal effect of specific substances is uncertain. We investigate whether adolescent cannabis and cigarette use is associated with incident depression and anxiety, while attempting to account for confounding and reverse causation.

Methods

We used data from ALSPAC, a UK birth cohort study, to investigate associations between cannabis or cigarettes (measured at age 16) and depression or anxiety (measured at age 18), before and after adjustment for pre-birth, childhood and adolescent confounders. Our imputed sample size was 4561 participants.

Results

Both cannabis (unadjusted OR 1.50, 95% CI 1.26, 1.80) and cigarette use (OR 1.37, 95% CI 1.16, 1.61) increased the odds of developing depression. Adjustment for pre-birth and childhood confounders partly attenuated these relationships though strong evidence of association persisted for cannabis use. There was weak evidence of association for cannabis (fully adjusted OR 1.30, 95% CI 0.98, 1.72) and insufficient evidence for association for cigarette use (fully adjusted OR = 0.97, 95% CI 0.75, 1.24) after mutually adjusting for each other, or for alcohol or other substance use. Neither cannabis nor cigarette use were associated with anxiety after adjustment for pre-birth and childhood confounders.

Conclusions

Whilst evidence of association between cannabis use and depression persisted after adjusting for pre-term and childhood confounders, our results highlight the difficulties in trying to estimate and interpret independent effects of cannabis and tobacco on psychopathology. Complementary methods are required to robustly examine effects of cannabis and tobacco on psychopathology.

Subclinical psychosis syndromes in the general population: results from a large-scale epidemiological survey among residents of the canton of Zurich, Switzerland

Aims. Prevalence and covariates of subclinical psychosis have gained increased interest in the context of early identification and treatment of persons at risk for psychosis. Methods. We analysed 9829 adults representative of the general population within the canton of Zurich, Switzerland. Two psychosis syndromes, derived from the SCL-90-R, were applied: 'schizotypal signs' and 'schizophrenia nuclear symptoms'. Results. Only a few subjects (13.2%) reported no schizotypal signs. While 33.2% of subjects indicated mild signs, only a small proportion (3.7%) reported severe signs. A very common outcome was no 'schizophrenia nuclear symptoms' (70.6%). Although 13.5% of the participants reported mild symptoms, severe nuclear symptoms were very rare (0.5%). Because these two syndromes were only moderately correlated (r = 0.43), we were able to establish sufficiently distinct symptom clusters. Schizotypal signs were more closely connected to distress than was schizophrenia nuclear symptoms, even though their distribution types were similar. Both syndromes were associated with several covariates, such as alcohol and tobacco use, being unmarried, low education level, psychopathological distress and low subjective well-being. Conclusions. Subclinical psychosis symptoms are quite frequent in the general population but, for the most part, are not very pronounced. In particular, our data support the notion of a continuous Wald distribution of psychotic symptoms in the general population. Our findings have enabled us to confirm the usefulness of these syndromes as previously assessed in other independent community samples. Both can appropriately be associated with well-known risk factors of schizophrenia.

Predictors of burnout: results from a prospective community study

The possible link between work strain and subsequent mental disorders has attracted public attention in many European countries. Burnout has become a favored concept within this context. Most burnout research has concentrated on various professional groups and less so on ordinary community samples. We analyzed the data collected from a 30-year community sample during seven measuring occasions, beginning in 1978. In the last assessment (2008), we included for the first time the Maslach Burnout Inventory (MBI). Making the diagnosis of a lifetime mental disorder a predictor for burnout required us to compile the cumulative prevalence rate over all seven occasions. We also evaluated various psycho-social predictors of burnout over the life cycle of our sample. Concurrent associations of the MBI with subscales from the SCL-90-R were also investigated. The relationship of burnout with several SCL-90-R subscales demonstrated that, in all dimensions, burnout is associated with significant psychopathology. Persons with a lifetime mood disorder, and especially those with a combination of mood and anxiety disorders, had a higher risk for subsequent burnout. Various partnership problems were another predictor for burnout. In conclusion, the role of mental disorder as an occupational illness remains controversial. Various forms of such disorders as well as some psycho-social predictors can predispose to burnout. By contrast, work-related predictors appear to be less important.

Associations of cannabis and cigarette use with psychotic experiences at age 18: findings from the Avon Longitudinal Study of Parents and Children

BACKGROUND

A clearer understanding of the basis for the association between cannabis use and psychotic experiences (PEs) is required. Our aim was to examine the extent to which associations between cannabis and cigarette use and PEs are due to confounding.

METHOD

A cohort study of 1756 adolescents with data on cannabis use, cigarette use and PEs.

RESULTS

Cannabis use and cigarette use at age 16 were both associated, to a similar degree, with PEs at age 18 [odds ratio (OR) 1.48, 95% confidence interval (CI) 1.18-1.86 for cannabis and OR 1.61, 95% CI 1.31-1.98 for cigarettes]. Adjustment for cigarette smoking frequency (OR 1.27, 95% CI 0.91-1.76) or other illicit drug use (OR 1.25, 95% CI 0.91-1.73) substantially attenuated the relationship between cannabis and PEs. The attenuation was to a lesser degree when cannabis use was adjusted for in the cigarette PE association (OR 1.42, 95% CI 1.05-1.92). However, almost all of the participants used cannabis with tobacco, including those who classed themselves as non-cigarette smokers.

CONCLUSIONS

Teasing out the effects of cannabis from tobacco is highly complex and may not have been dealt with adequately in studies to date, including this one. Complementary methods are required to robustly examine the independent effects of cannabis, tobacco and other illicit drugs on PEs.

Suicidality in the prospective Zurich study: prevalence, risk factors and gender

Our prospective Zurich study (1978-2008) found that suicidal ideation had occurred in 40.5% and suicide attempts in 6.6% of the population by age 50. Important gender differences were found in both suicidality and its risk factors. Suicide attempts were earlier and more frequent among women than among men: 70 versus 44% reported their first suicide attempt before 20. For women, the relative risk of suicide attempts was 1.6, but the relative risk of suicidal ideation was about equal (1.1 for women). The main risk factors for suicidal ideation in women were low social support (OR 4.0) and frequent punishment in childhood (OR 3.7), and in men, a depressive (OR 6.5) and an anxious personality (OR 4.6). The main risk factors for suicide attempts in women were a broken home (OR 10.2) and sexual abuse/violence (OR 7.9) in childhood; in men, no multivariate analyses of suicide attempt were conducted because of insufficient statistical power.

Cannabis use is a better indicator of poor mental health in women than in men: a cross-sectional study in young adults from the general population

Cannabis use is a known risk factor for a range of mental health problems, but less is known on the association with general mental health. We aim to explore the relationship between cannabis use and general mental health. We did a cross-sectional online survey of 1,929 young adults aged 18-30 years. Participants reported socio-demographic data, substance use and the Symptom Checklist-90 (SCL-90). Monthly cannabis use was associated with a higher total score on the SCL-90, both in a crude (OR 1.94, 95% CI 1.57-2.38) and fully adjusted model (OR 1.48, 95% CI 1.07-2.03). The association between cannabis and mental health was stronger in women and weekly users, and was independent of age at first use of cannabis. We conclude that moderate cannabis use is associated with general mental health problems in young adulthood. This relationship is independent of age at first use and of other risk factors, and is strongest in women.

Associations with quality of life and the effect of psychopathology in a community study

PURPOSE

Quality of life (QoL) is considerably impaired in mental illness and especially in depression. In this study, we aimed to determine the demographic, personality-related and psychopathological associations with QoL. In addition, we studied how the associations with QoL differ depending on the burden of psychopathology.

METHODS

We used a longitudinal observational cohort study, enriched for high levels of psychopathology, to examine data for QoL when the subjects were 34-35. We conducted a hierarchical linear regression analysis to determine how sex, personality, sociodemographics, somatic symptoms and psychopathology affect QoL.

RESULTS

Once all the variables were included in the model, total psychopathology is strongly negatively associated with QoL, while mastery and income were shown to have positive associations with QoL. Sex, personality and somatic symptoms had no significant associations with QoL once the other variables had been introduced into the regression. Due to the outstanding association with psychopathology, we tested whether the relationship had any interaction with the other predictors, but none reached statistical significance.

CONCLUSIONS

The most important association with QoL is psychopathology, regardless of sex, personality, coping resources, sociodemographics or the extent somatic symptoms. The relationship holds across the other variables included and the results are, thus, widely applicable.

Transcription factor 4 (TCF4) and schizophrenia: integrating the animal and the human perspective

Schizophrenia is a genetically complex disease considered to have a neurodevelopmental pathogenesis and defined by a broad spectrum of positive and negative symptoms as well as cognitive deficits. Recently, large genome-wide association studies have identified common alleles slightly increasing the risk for schizophrenia. Among the few schizophrenia-risk genes that have been consistently replicated is the basic Helix-Loop-Helix (bHLH) transcription factor 4 (TCF4). Haploinsufficiency of the TCF4 (formatting follows IUPAC nomenclature: TCF4 protein/protein function, Tcf4 rodent gene cDNA mRNA, TCF4 human gene cDNA mRNA) gene causes the Pitt-Hopkins syndrome-a neurodevelopmental disease characterized by severe mental retardation. Accordingly, Tcf4 null-mutant mice display developmental brain defects. TCF4-associated risk alleles are located in putative coding and non-coding regions of the gene. Hence, subtle changes at the level of gene expression might be relevant for the etiopathology of schizophrenia. Behavioural phenotypes obtained with a mouse model of slightly increased gene dosage and electrophysiological investigations with human risk-allele carriers revealed an overlapping spectrum of schizophrenia-relevant endophenotypes. Most prominently, early information processing and higher cognitive functions appear to be associated with TCF4 risk genotypes. Moreover, a recent human study unravelled gene × environment interactions between TCF4 risk alleles and smoking behaviour that were specifically associated with disrupted early information processing. Taken together, TCF4 is considered as an integrator ('hub') of several bHLH networks controlling critical steps of various developmental, and, possibly, plasticity-related transcriptional programs in the CNS and changes of TCF4 expression also appear to affect brain networks important for information processing. Consequently, these findings support the neurodevelopmental hypothesis of schizophrenia and provide a basis for identifying the underlying molecular mechanisms.

Impact of childhood adversity on the onset and course of subclinical psychosis symptoms--results from a 30-year prospective community study

The study objective was to examine childhood adversity in association with intra-individual changes and inter-individual differences in subclinical psychosis in a representative community cohort over a 30-year period of observation. We analyzed two psychosis syndromes derived from the SCL-90-R - schizotypal signs and schizophrenia nuclear symptoms - in 335 participants. Participants were repeatedly assessed between 1978 (around age 20) and 2008 (around age 50). We focused specifically on inter-individual differences and intra-individual changes over time by applying structural equation modeling, generalized linear models, and generalized estimating equations. Several weak inter-individual differences revealed that increased schizotypal signs are related to various childhood adversities, such as being repeatedly involved in fights and parents having severe conflicts among themselves. We also found a significant positive association between schizotypal signs and the total number of adversities a subject experienced. This pointed toward a modest dose-response relationship. The intra-individual change in schizotypal signs over time was rather weak, although some adjustment did occur. In contrast, inter-individual schizophrenia nuclear symptoms were mainly unrelated to childhood adversity. However, some striking intra-individual changes in distress were noted over time, especially those linked with severe punishment and the total adversity score. In conclusion, we have confirmed previous positive findings about the association between childhood adversity and subsequent subclinical psychosis symptoms: An increase in adversity is weakly related to an increase of the psychosis symptom load. However, depending on the kind of adversity experienced the psychosis symptom load decreases gradually in adult life.

Cigarette smoking and cannabis use are equally strongly associated with psychotic-like experiences: a cross-sectional study in 1929 young adults

BACKGROUND

Cannabis use is associated with increased risk for psychotic-like experiences (PLEs) and psychotic disorders. It remains unclear whether this relationship is causal or due to confounding.

METHOD

A total of 1929 young adults aged 18-30 years participated in a nationwide internet-based survey in The Netherlands and gave information on demographics, substance use and parental psychiatric illness and completed the Community Assessment of Psychic Experiences (CAPE).

RESULTS

Cigarette smoking and cannabis use were equally strongly associated with the frequency of PLEs in a fully adjusted model (β = 0.098 and 0.079 respectively, p < 0.05). Cannabis use was associated with distress from PLEs in a model adjusted for an elaborate set of confounders excluding smoking (β = 0.082, p < 0.05). However, when cigarette smoking was included in the model, cannabis use was not a significant predictor of distress from PLEs. Cigarette smoking remained associated with distress from PLEs in a fully adjusted model (β = 0.107, p < 0.001).

CONCLUSIONS

Smoking is an equally strong independent predictor of frequency of PLEs as monthly cannabis use. Our results suggest that the association between moderate cannabis use and PLEs is confounded by cigarette smoking.

Deconstructing sub-clinical psychosis into latent-state and trait variables over a 30-year time span

BACKGROUND

Our aim was to deconstruct the variance underlying the expression of sub-clinical psychosis symptoms into portions associated with latent time-dependent states and time-invariant traits.

METHODS

We analyzed data of 335 subjects from the general population of Zurich, Switzerland, who had been repeatedly measured between 1979 (age 20/21) and 2008 (age 49/50). We applied two measures of sub-clinical psychosis derived from the SCL-90-R, namely schizotypal signs (STS) and schizophrenia nuclear symptoms (SNS). Variance was decomposed with latent state-trait analysis and associations with covariates were examined with generalized linear models.

RESULTS

At ages 19/20 and 49/50, the latent states underlying STS accounted for 48% and 51% of variance, whereas for SNS those estimates were 62% and 50%. Between those age classes, however, expression of sub-clinical psychosis was strongly associated with stable traits (75% and 89% of total variance in STS and SNS, respectively, at age 27/28). Latent states underlying variance in STS and SNS were particularly related to partnership problems over almost the entire observation period. STS was additionally related to employment problems, whereas drug-use was a strong predictor of states underlying both syndromes at age 19/20. The latent trait underlying expression of STS and SNS was particularly related to low sense of mastery and self-esteem and to high depressiveness.

CONCLUSIONS

Although most psychosis symptoms are transient and episodic in nature, the variability in their expression is predominantly caused by stable traits. Those time-invariant and rather consistent effects are particularly influential around age 30, whereas the occasion-specific states appear to be particularly influential at ages 20 and 50.

The prevalence of substance use disorders and psychiatric disorders as a function of psychotic symptoms

BACKGROUND

Psychotic symptoms represent one of the most severe and functionally impairing components of several psychological disorders. One group with particularly high rates of psychotic symptoms is chronic substance users. However, the literature on psychotic symptoms and substance use is quite narrow and has focused almost exclusively on drug-induced psychosis, neglecting the population of substance users with psychotic symptoms occurring independently of acute drug effects.

METHOD

The current study examined demographics, substance dependence, and psychiatric comorbidities among substance users with current (CurrSx), past (PastSx), and no psychotic symptoms (NoSx). Patients (n=685) were sequential admissions to a residential substance use treatment center from 2006 to 2009.

RESULTS

Compared to NoSx, those who endorsed CurrSx were significantly more likely to meet criteria for lifetime alcohol dependence and lifetime amphetamine dependence. CurrSx were more likely than PastSx to meet for lifetime cannabis dependence. Additionally, CurrSx were more likely to meet criteria for a comorbid psychiatric disorder compared to NoSx, and evidenced a greater number of current psychiatric disorders. NoSx were less likely than both CurrSx and PastSx to meet criteria for Borderline Personality Disorder.

CONCLUSION

Individuals with non-substance induced psychotic symptoms appear to meet criteria for specific substance use disorders and psychiatric disorders at higher rates than those without psychotic symptoms; these effects were most evident for those with current as opposed to past symptoms. Findings suggest that these individuals may need specialized care to address potential psychiatric comorbidities and overall greater severity levels relative to substance users without psychotic symptoms.

Psychosis Following Traumatic Brain Injury

Psychosis following traumatic brain injury (PFTBI) has received modest empirical investigation, and is subsequently poorly understood, identified and treated. The current article reports on consistencies in PFTBI phenomenology according to the existing peer-reviewed literature. The potential for psychotic symptoms post TBI, aetiological propositions, prevalence, significance of onset latency and injury severity, clinical and cognitive neuropsychological presentation and injury localisation/neuroimaging data are reviewed. Substantial methodological limitations associated with the majority of publications informing this work are also discussed. Despite controversies in the literature, psychosis following TBI appears to be three times more prevalent than psychotic disorders in the general population, and comparable in presentation to other idiopathic psychotic spectrum disorders, including schizophrenia.

Cannabis use and vulnerability for psychosis in early adolescence--a TRAILS study

AIMS

To examine the direction of the longitudinal association between vulnerability for psychosis and cannabis use throughout adolescence.

DESIGN

Cross-lagged path analysis was used to identify the temporal order of vulnerability for psychosis and cannabis use, while controlling for gender, family psychopathology, alcohol use and tobacco use.

SETTING

A large prospective population study of Dutch adolescents [the TRacking Adolescents' Individual Lives Survey (TRAILS) study].

PARTICIPANTS

A total of 2120 adolescents with assessments at (mean) age 13.6, age 16.3 and age 19.1.

MEASUREMENTS

Vulnerability for psychosis at the three assessment points was represented by latent factors derived from scores on three scales of the Youth Self-Report and the Adult Self-Report, i.e. thought problems, social problems and attention problems. Participants self-reported on cannabis use during the past year at all three waves.

FINDINGS

Significant associations (r = 0.12-0.23) were observed between psychosis vulnerability and cannabis use at all assessments. Also, cannabis use at age 16 predicted psychosis vulnerability at age 19 (Z = 2.6, P < 0.05). Furthermore, psychosis vulnerability at ages 13 (Z = 2.0, P < 0.05) and 16 (Z = 3.0, P < 0.05) predicted cannabis use at, respectively, ages 16 and 19.

CONCLUSIONS

Cannabis use predicts psychosis vulnerability in adolescents and vice versa, which suggests that there is a bidirectional causal association between the two.

Stronger evidence is needed before accepting that cannabis plays an important role in the aetiology of schizophrenia in the population

Schizophrenia is a debilitating but poorly understood condition with very few known modifiable risk factors. Cannabis use can acutely induce psychotic experiences, but its causal relationship to schizophrenia is less well understood. Longitudinal cohort studies suggest that the association between cannabis and psychotic outcomes is not due to chance or reverse causation. However, the association could be due to bias or residual confounding. Methods that can test alternative explanations in greater depth are required. This is especially important as ecological studies have found little association between the increase in cannabis use over recent decades and incidence of psychotic disorders; public health models suggest that cannabis use may need to be treated and prevented in many thousands of users in order to prevent one case of schizophrenia. We believe that, while such uncertainty exists, there is a scientific duty to continue to investigate the role of cannabis in the aetiology of schizophrenia and that the policy case for considering cannabis exposure as a critical target for preventing schizophrenia is yet to be made. However, due to other evidence of the harms of cannabis use, this should not affect the public health message that cannabis can be harmful and that cannabis dependence should be prevented.

Moderating effects of race in clinical trial participation and outcomes among marijuana-dependent young adults

BACKGROUND

Few studies have examined clinical trial participation rates and treatment outcomes among underserved young adults who are dependent on marijuana, the most commonly abused illicit drug.

METHOD

The present study was a secondary analysis of a trial of court-referred marijuana-dependent young adults (ages 18-25) randomized to one of four treatment conditions: Motivational Enhancement Therapy/Cognitive Behavioral Therapy (MET/CBT), MET/CBT+Contingency Management (CM), Drug Counseling (DC) or DC+CM. African American (N=81) participants were compared to White (N=31) participants with respect to rates of participation in phases of treatment and substance use outcomes. In addition, the interaction of race and treatment condition was examined to ascertain if the interventions yielded different effects based on race.

RESULTS

Among those who started treatment, African American young adults were significantly less likely to complete the treatment and posttreatment phases of the clinical trial than their White counterparts. Irrespective of treatment type, substance use outcomes (i.e., percentage of marijuana-negative specimens and longest duration of continuous abstinence) did not vary by race. However, there was a significant interaction effect between treatment type and race; African American young adults did not benefit differentially from any specific type of treatment, but CM was effective in reducing proportion of marijuana positive samples among White young adults.

CONCLUSIONS

Findings suggest that clinical trial treatment and posttreatment completion rates vary by race in this population, as does response to specific treatment types. More treatment research focusing specifically on African American marijuana-dependent young adults is warranted.

Sex differences in sub-clinical psychosis--results from a community study over 30 years

Sex differences in schizophrenia have long been reported. They are found within almost all aspects of the disease, from incidence and prevalence, age of onset, symptomatology, and course to its psycho-social outcome. Many sex-related hypotheses have been developed about the biology, psychology, or sociology of that disease. A further approach to study sex differences would be to examine such differences in sub-clinical psychotic states as well. If factors related to full-blown psychosis were equally meaningful over the entire psychosis continuum, we should expect that "true" sex differences could also be identified in sub-clinical psychosis. Here, we studied sex differences in sub-clinical psychosis within a community cohort in Zurich, Switzerland. This population was followed for over 30 years and included males and females between the ages of 20/21 and 49/50. We applied two different measures of sub-clinical psychosis representing schizotypal signs and schizophrenia nuclear symptoms. Using cross-sectional and longitudinal analyses, we found no significant sex differences in sub-clinical psychosis over time with respect to age of onset, symptomatology, course, or psycho-social outcome. Thus it appears that sex differences in psychosis manifest themselves at the high end of the continuum (full-blown schizophrenia) rather than within the sub-threshold range. Possibly males and females have separate thresholds for certain symptoms because they are differently vulnerable or exposed to various risk factors.

Schizophrenia risk polymorphisms in the TCF4 gene interact with smoking in the modulation of auditory sensory gating

Several polymorphisms of the transcription factor 4 (TCF4) have been shown to increase the risk for schizophrenia, particularly TCF4 rs9960767. This polymorphism is associated with impaired sensorimotor gating measured by prepulse inhibition--an established endophenotype of schizophrenia. We therefore investigated whether TCF4 polymorphisms also affect another proposed endophenotype of schizophrenia, namely sensory gating assessed by P50 suppression of the auditory evoked potential. Although sensorimotor gating and sensory gating are not identical, recent data suggest that they share genetic fundamentals. In a multicenter study at six academic institutions throughout Germany, we applied an auditory P50 suppression paradigm to 1,821 subjects (1,023 never-smokers, 798 smokers) randomly selected from the general population. Samples were genotyped for 21 TCF4 polymorphisms. Given that smoking is highly prevalent in schizophrenia and affects sensory gating, we also assessed smoking behavior, cotinine plasma concentrations, exhaled carbon monoxide, and the Fagerström Test (FTND). P50 suppression was significantly decreased in carriers of schizophrenia risk alleles of the TCF4 polymorphisms rs9960767, rs10401120rs, rs17597926, and 17512836 (P < 0.0002-0.00005). These gene effects were modulated by smoking behavior as indicated by significant interactions of TCF4 genotype and smoking status; heavy smokers (FTND score ≥ 4) showed stronger gene effects on P50 suppression than light smokers and never-smokers. Our finding suggests that sensory gating is modulated by an interaction of TCF4 genotype with smoking, and both factors may play a role in early information processing deficits also in schizophrenia. Consequently, considering smoking behavior may facilitate the search for genetic risk factors for schizophrenia.