Cannabis sativa use in adolescence and risk of psychosis: a systematic review / Uso de cannabis sativa na adolescência e risco de psicose: uma revisão sistemática

Background: Studies have pointed out the increased risk of developing psychosis in adulthood related to cannabis use during adolescence. Aim: To conduct a systematic review of the literature on the use of cannabis in adolescence and risk of psychosis. Method: We conducted a systematic review in accordance with PRISMA guidelines. We searched by PubMed, PsycINFO, and SciELO database between 2010 and 2019. Results: After an accurate analysis, of the 8.673 records screened articles, we selected and included 32 original studies in this systematic review. The sample in the original papers totaled 81.049 participants, indicating an association between early use of cannabis and the onset of psychosis in 97.3% of the studies, with a robust variety of instruments used. It has been shown that early cannabis use, associated to genetic vulnerability, gender, duration of use, environmental and social factors, or the use of other drugs may lead to late development of schizophrenia whether compared with non-users. Conclusion: There is evidence that marijuana use is associated with the occurrence of psychosis in adolescence and later in life. However, other variables, such as social and biological aspects, should be considered. This shows the importance of educational programs of public policies on risks of cannabis and clear information to the population about several combination factors that might lead to trigger psychotic disorders, such as schizophrenia.