188. Does Cannabis Use Worsen Psychotic Symptom Presentation?

Abstract

Background: While the relationship between cannabis and psychosis is well established, there is a lack of studies into whether cannabis use is associated with a particular pattern of symptoms at psychosis onset. Moreover, there is much evidence that psychotic experiences are common in the healthy population, and again their relationship with exposure to cannabis has been scarcely studied. We hypothesized that psychopathology in frst-episode psychosis patients (FEP), and psychotic experiences in controls, would be qualitatively and quantitatively affected by pattern of cannabis use. Methods: The Operational CRITeria (OPCRIT) system, the CAPE (Community Assessment of Psychic Experiences), and the CEQ (Cannabis Experience Questionnaire) were used for assessing clinical/subclinical symptoms and pattern of cannabis use in 1200 FEP and 1500 controls across 15 European sites. Three different methods were tested to aggregate OPCRIT items in dimen-sions: principal component analysis (PCF), confrmatory factor analysis (CFA) in structural equation modeling, and item response theory (IRT). Number of components to extract in PCF was determined by Monte Carlo simulation, using R. In all factor analyses, composite scores for each symptom dimension were predicted by regression, and the main effect of cannabis on such dimensions was tested after analysis of variance. Results: The sample was good (MSA = 0.84) and data suitable for factor analyses (Bartlett sphericity test, χ2(1830) = 20 252, P