Better social but worse academic premorbid adjustment in cannabis-users psychotic patients across Europe

Abstract

Background: Several studies report that patients with psychosis who used cannabis have a better cognitive performance than those whodid not (Rabin et al. 2011). In a previous study we found out a higher premorbid IQ, and a better IQ in psychotic patients who smoked cannabis in their lifetime, and our findings were consistent with the idea that this association is due to a better premorbid functioning rather than to an ameliorative effect of cannabis use on cognitive performance (Ferraro et al., 2013). A number of authors have hypothesized that psychotic patients who consume cannabis constitute a differentiated subgroup of patients that have better cognitive and social skills, necessary to engage in illegal drug consumption, than non-using patients (Compton et al., 2011; Løberg et al., 2014; Arnold et al., 2015). Given that the prevalence, and patterns, of cannabis use are culturally driven, we wanted to test the hypothesis of a better premorbid functioning in First Episode Psychosis (FEP) cannabis-using and non-using patients coming from different European countries (England, Italy, Spain, France, the Netherlands) as part of the EUGEI-STUDY. Methods: 1.745 people (746 cases; 999 controls) completed the assessment for Intellectual Quotient (IQ) (WAIS-brief version) premorbid adjustment (Premorbid Adjustment Scale – PAS) and cannabis use (CEQ-Revised). We first performed a factor analysis on PAS components, by obtaining two main factors: “Premorbid Social Adjustment” (PSA) and “Premorbid Academic Adjustment” (PAA). We therefore performed linear mixed models with IQ, PSA, and PAA as dependent variables and cannabis lifetime (Yes/No), subject status (Cases/Controls), gender and age as independent variables. Results: Across all countries, IQ was higher in those patients who smoked cannabis in their lifetime compared to those who did not (P = 0.027). This IQ difference was only 3 points and was the same for cases and healthy controls (P = 0.949). Similarly, patients who had smoked cannabis in their lifetime showed better PSA scores than non users (P = 0.009). The difference in PSA score between cannabis-users and non-users was significantly greater in cases than controls (P = 0.038). Conversely, across all countries, PAA resulted worst in patients who smoked cannabis lifetime than patients who did not (Po0.001) and this PAA score difference was the same for cases and controls (P = 0.693). Discussion: Our cannabis-using FEP patients have higher IQ, better PSA and lower PAA than non user patients across 5 different European countries. Starting from these preliminary results, we can conclude that a better PSA is significantly associated with cannabis use in FEP patients. Nevertheless, in an exploratory analysis, a better IQ resulted related to a better PAA (o0.001) but not to PSA (P = 0.260); thus indicating an independent relationship of IQ and PSA with cannabis use. Further analysis are required in order to model these multivariate relationships.