Background Cannabis use is associated with increased risk of later psychotic disorder but whether it affects incidence of the disorder remains unclear. We aimed to identify patterns of cannabis use with the strongest effect on odds of psychotic disorder across Europe and explore whether differences in such patterns contribute to variations in the incidence rates of psychotic disorder. Methods We included patients aged 18-64 years who presented to psychiatric services in 11 sites across Europe and Brazil with first-episode psychosis and recruited controls representative of the local populations. We applied adjusted logistic regression models to the data to estimate which patterns of cannabis use carried the highest odds for psychotic disorder. Using Europe-wide and national data on the expected concentration of Δ⁹-tetrahydrocannabinol (THC) in the different types of cannabis available across the sites, we divided the types of cannabis used by participants into two categories: low potency (THC <10%) and high potency (THC ≥10%). Assuming causality, we calculated the population attributable fractions (PAFs) for the patterns of cannabis use associated with the highest odds of psychosis and the correlation between such patterns and the incidence rates for psychotic disorder across the study sites. Findings Between May 1, 2010, and April 1, 2015, we obtained data from 901 patients with first-episode psychosis across 11 sites and 1237 population controls from those same sites. Daily cannabis use was associated with increased odds of psychotic disorder compared with never users (adjusted odds ratio [OR] 3•2, 95% CI 2•2-4•1), increasing to nearly five-times increased odds for daily use of high-potency types of cannabis (4•8, 2•5-6•3). The PAFs calculated indicated that if high-potency cannabis were no longer available, 12•2% (95% CI 3•0-16•1) of cases of first-episode psychosis could be prevented across the 11 sites, rising to 30•3% (15•2-40•0) in London and 50•3% (27•4-66•0) in Amsterdam. The adjusted incident rates for psychotic disorder were positively correlated with the prevalence in controls across the 11 sites of use of high-potency cannabis (r = 0•7; p=0•0286) and daily use (r = 0•8; p=0•0109). Interpretation Differences in frequency of daily cannabis use and in use of high-potency cannabis contributed to the striking variation in the incidence of psychotic disorder across the 11 studied sites. Given the increasing availability of high-potency cannabis, this has important implications for public health.

This study confirmed marked heterogeneity in risk for psychotic disorders by person and place, including higher rates in younger men, racial/ethnic minorities, and areas characterized by a lower percentage of owner-occupied houses.

No abstract

Aim: Violence risk prediction is a priority issue for clinicians working with mentally disordered offenders. The aim of the present study was to determine violence risk factors in acute psychiatric inpatients. Methods:The study was conducted in a locked, short-term psychiatric inpatient unit and involved 374 patients consecutively admitted in a 1-year period. Sociodemographic and clinical data were obtained through a review of the medical records and patient interviews. Psychiatric symptoms at admission were assessed using the Brief Psychiatric Rating Scale (BPRS). Psychiatric diagnosis was formulated using the Structured Clinical Interview for DSM-IV. Past aggressive behavior was evaluated by interviewing patients, caregivers or other collateral informants. Aggressive behaviors in the ward were assessed using the Overt Aggression Scale. Patients who perpetrated verbal and against-object aggression or physical aggression in the month before admission were compared to non-aggressive patients, moreover, aggressive behavior during hospitalization and persistence of physical violence after admission were evaluated.Results: Violent behavior in the month before admission was associated with male sex, substance abuse and positive symptoms. The most significant risk factor for physical violence was a past history of physically aggressive behavior. The persistent physical assaultiveness before and during hospitalization was related to higher BPRS total scores and to more severe thought disturbances. Higher levels of hostility-suspiciousness BPRS scores predicted a change for the worse in violent behavior, from verbal to physical. Conclusion:A comprehensive evaluation of the history of past aggressive behavior and psychopathological variables has important implications for the prediction of violence in psychiatric settings.

Recent years have seen considerable progress in epidemiological and molecular genetic research into environmental and genetic factors in schizophrenia, but methodological uncertainties remain with regard to validating environmental exposures, and the population risk conferred by individual molecular genetic variants is small. There are now also a limited number of studies that have investigated molecular genetic candidate gene-environment interactions (G × E), however, so far, thorough replication of findings is rare and G × E research still faces several conceptual and methodological challenges. In this article, we aim to review these recent developments and illustrate how integrated, large-scale investigations may overcome contemporary challenges in G × E research, drawing on the example of a large, international, multi-center study into the identification and translational application of G × E in schizophrenia. While such investigations are now well underway, new challenges emerge for G × E research from late-breaking evidence that genetic variation and environmental exposures are, to a significant degree, shared across a range of psychiatric disorders, with potential overlap in phenotype.