Cannabis use disorder and suicide attempts in bipolar disorder: A meta-analysis.

We aimed at clarifying the strength and consistency of the association between cannabis use disorder and suicide attempts in bipolar disorder. We conducted a systematic review and meta-analysis of observational studies providing cross-sectional and longitudinal data on this association. We screened articles indexed in Medline, Embase, PsycINFO databases up to July 2018. The random-effects meta-analysis, based on 6375 subjects from eleven studies, estimated a cross-sectional association between cannabis use disorder and history of suicide attempts (OR = 1.35; p = 0.01; I2 = 41.7%). Meta-regression analyses showed that effect size was not influenced by any study characteristics. Publication bias was not detectable. We could not perform a meta-analysis exploring the longitudinal association between cannabis use disorder and suicide attempts, due to the lack of suitable data. The current evidence highlights a weak association between cannabis use disorder and suicidal attempts in bipolar disorder. Due to the cross-sectional design of included studies, causal inferences could not be explored.