Sideli L, et al. - Researchers sought to address how cannabis use is correlated with psychotic, bipolar, depressive, and anxiety disorders, as well as suicide. Epidemiological evidence from cross-sectional and long-term prospective studies was synthesized and possible etiological mechanisms were considered in this work. Both observational and experimental studies provided evidence confirming that cannabis use plays an important role in the initiation and persistence of psychotic disorders. The extent of cannabis use determined the size of the effect, with early cannabis use and the use of high-potency varieties and synthetic cannabinoids correlated with greater risk. Further, frequent cannabis use also seemed increasing the risk for mania as well as for suicide. However, no clear evidence confirming the effect on depression and on anxiety was gained. Furthermore, reverse causality may be involved in the relationship with common mental disorders, as depression and anxiety are described to result in greater cannabis consumption in some studies. Pathogenetic mechanisms focus on the influence of tetrahydrocannabinol (THC, the main psychoactive ingredient of cannabis) associating with genetic predisposition and possibly other environmental risk factors. The psychotogenic effects of THC are ameliorated by cannabidiol (CBD), the other important ingredient of traditional cannabis, but the high-potency varieties that are increasingly available lack CBD.