Cannabis use in adolescence and risk of psychosis: Are there factors that moderate this relationship? A systematic review and meta-analysis

Abstract

Background: Previous research has reported increased risk for psychosis among individuals who use cannabis during adolescence. We conducted a systematic review and meta-analysis to investigate the interaction between adolescent cannabis use and other factors in moderating risk for psychosis later in life. Method: We searched four electronic databases in June 2020 for articles that assessed adolescent cannabis use, had psychosis as an outcome and analyzed for the association between adolescent cannabis use and psychosis. Analysis was done using random-effects meta-analysis and narrative synthesis. Results: A total of 63 studies were included in the narrative review and 18 studies were included in the meta-analysis. Adolescent cannabis use was found to increase risk for psychosis (RR = 1.71 (95%CI, 1.47–2.00, p < 0.00001) and predict earlier onset of psychosis. The following factors moderate the relationship between cannabis use and the risk of psychosis: age of onset of cannabis use, frequent cannabis use, exposure to childhood trauma, concurrent use of other substances and genetic factors. Conclusion: Adolescent cannabis use is associated with an increased risk for psychosis later in life. In addition, there are factors that moderate this relationship; therefore there is a need for research to assess the interaction between these factors, adolescent cannabis use and psychosis risk.

Keywords:

• Adolescence
• cannabis
• psychosis
• moderating factors

Acknowledgement

The authors would like to acknowledge Mr. Albert Tele for his guidance and support in analysis of data. No external funding was received for this research.

Author contributions

SKK was involved in conception, design, conducting the search, review of articles for review, interpretation of data and drafting the manuscript. KM was involved in conducting the search, selection of articles, data synthesis and analysis and drafting and review of the manuscript. NV was involved in developing the search strategy and data synthesis and analysis. MTL was a supervisor in this project and he was involved in review of design, search terms and review of articles included in the review. All authors reviewed the manuscript.