O3.1. ASSOCIATION OF EXTENT OF CANNABIS USE AND ACUTE INTOXICATION EXPERIENCES IN A MULTI-NATIONAL SAMPLE OF FIRST EPISODE PSYCHOSIS PATIENTS AND CONTROLS

Background FEP patients who use cannabis experience more frequent intoxication experiences compared to controls. It is not clear whether this is consequent to patients being more vulnerable to the effects of cannabis use or to their heavier pattern of use. We aimed to determine whether extent of use predicted psychotic-like and euphoric intoxication experiences in FEP patients and controls and whether this differs between groups. Methods We analysed data on lifetime cannabis using patients (n=655) and controls (n=654) across 15 sites from six countries in the EU-GEI study (2010–2015). We used multiple regression to model predictors of cannabis-induced experiences and Factorial ANOVA to determine if there was an interaction between caseness and extent of use. Results Both psychotic-like and euphoric experiences were more frequent in cases vs controls (p<0.001). Increased frequency of use and money spent on cannabis were associated with increased experiences. For psychotic-like experiences there was a significant interaction for caseness x frequency of use (p=0.004) and caseness x money spent on cannabis (p=0.023) such that FEP patients had increased experiences compared to controls. There was no similar significant interaction for euphoric experiences. Discussion FEP patients are particularly sensitive to increased psychotic like, but not euphoric experiences, at higher frequency and amount of cannabis use compared to controls. This suggests a specific psychotomimetic response in patients related particularly to heavy cannabis use. Reducing use may be a strategy for minimizing psychotic-like experiences in FEP.