Comorbidity of Psychotic Disorders and Cannabis Use

Cannabis is the most widely used illicit drug in the world. The prevalence of cannabis use is higher among individuals with psychosis than in the general population. The causal nature of the association between cannabis and psychosis is still a matter of debate and there are practical difficulties in distinguishing between substance-induced and independent psychoses. There is a general consensus that cannabis use increases the risk of developing psychotic disorders among vulnerable or predisposed individuals and can negatively affect the course of pre-existing chronic psychosis. Individuals with expression of vulnerability to psychosis may be more likely to start using cannabis so as to ‘‘self-medicate’’ their distress. The aim of this work is to review the available literature about the comorbidity of psychotic disorders and cannabis use trying to find answers to these questions: -Are subjects with incipient psychosis use cannabis as self-medication? -Do cannabis users exhibit a higher risk of developing a psychotic disorder? -Does cannabis use worsen the course of established schizophrenia?.