While the legal status and public perception of cannabis are currently changing in many countries, one of the important considerations from a public health viewpoint is its potential association with adverse health outcomes such as the development of psychosis. We conducted an umbrella review of systematic reviews and meta-analyses using the AMSTAR-2 to assess the quality of included reviews. We further created an evidence map to visualize and facilitate the overview of the published evidence synthesis on the association between cannabis use and all psychosis-related outcomes and risk moderators in healthy, high-risk, and clinical populations. Overall, we found 32 systematic reviews and meta-analyses. Based on a synthesis of current evidence, cannabis use is associated with subclinical psychosis states (psychotic-like experiences) and traits (schizotypal personality) in the healthy population, as well as earlier onset and development of psychosis. An association with the clinical-high-risk state for psychosis, attenuated psychosis symptoms and transition to psychosis in this population could not be confirmed. An association between cannabis use and psychosis outcomes in patients with psychotic disorder could solely be confirmed regarding relapse. Whether causal effects underlie those associations has not sufficiently been addressed in the evidence synthesis to date.
Keywords: Clinical high-risk for psychosis; Marijuana; Psychotic disorders; Psychotic-like-experiences; Relapse; Schizophrenia; Schizotypy.
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