Objective: This critique discusses the partnership involving cannabis use and psychotic, bipolar, depressive, and anxiousness issues, as nicely as suicide. It summarizes epidemiological proof from cross-sectional and lengthy-term potential research and considers probable etiological mechanisms. Strategies: Systematic evaluations and methodologically robust research in the field (from inception to February 2019) had been identified employing a extensive search of Medline, PsychINFO, and Embase and summarized employing a narrative synthesis. Final results: Constant proof, each from observational and experimental research, has confirmed the essential function of cannabis use in the initiation and persistence of psychotic issues. The size of the impact is associated to the extent of cannabis use, with higher danger for early cannabis use and use of higher-potency varieties and synthetic cannabinoids. Accumulating proof suggests that frequent cannabis use also increases the danger for mania as nicely as for suicide. Even so, the impact on depression is much less clear and findings on anxiousness are contradictory with only a couple of methodologically robust research. Additionally, the partnership with frequent mental issues may perhaps involve reverse causality, as depression and anxiousness are reported to lead to higher cannabis consumption in some research. Pathogenetic mechanisms concentrate on the impact of tetrahydrocannabinol (THC, the major psychoactive ingredient of cannabis) interacting with genetic predisposition and probably other environmental danger variables. Cannabidiol (CBD), the other essential ingredient of standard cannabis, ameliorates the psychotogenic effects of THC but is absent from the higher-potency varieties that are increasingly obtainable. Conclusions: The proof that heavy use of higher-THC/low-CBD forms of cannabis increases the danger of psychosis is sufficiently robust to merit public well being education. Proof of related but smaller sized effects in mania and suicide is increasing, but is not convincing for depression and anxiousness. There is substantially present interest in the possibility that CBD may perhaps be therapeutically beneficial.