Heavy cannabis use impairs verbal memory of first psychotic episode patients

Abstract

IntroductionCannabis consumption is known to be increased in both schizophrenic and first psychotic episode patients. Contrary to what has been reported in studies with healthy people, all published studies so far have reported no impairments or even beneficial effects on neurocognition associated with cannabis consumption in schizophrenia and first psychotic episode patients. However, these studies did not address the effects of very high cannabis consumption.ObjectiveOur aim in this study was to assess the effects on neurocognition of regular and heavy cannabis consumption in first psychotic episode patients.MethodsA total of 74 patients were included in the study and assigned to 3 different groups according to their mean cannabis consumption during the last year (non-users, regular users, and heavy users). Participants were administered verbal memory, attention, processing speed, working memory, vocabulary, arithmetic and spatial orientation tasks.ResultsOur results showed the heavy cannabis group of first psychotic episode patients to be significantly impaired in all the verbal memory measures with respect to the non-users group. There were no significant differences between regular users and non-users. Moreover, regular cannabis consumption was associated with an improvement in some attention and processing speed measures.ConclusionsOur data showed heavy cannabis consumption to impair verbal memory in first psychotic episode patients and suggest a dose-related effect of cannabis consumption, since regular consumption did not impair verbal memory and may be beneficial for other tasks.Disclosure of interestThe authors have not supplied their declaration of competing interest.