As with psychosis, there is limited evidence that depression and suicidal ideation cause an increase in cannabis use, putatively via mechanisms of self-medication (78). While some researchers have found support for cannabis use exerting a causal influence on depression and suicide (79), others posit that confounding factors, which lead to a network of correlated risk influences is responsible (80). We are aware of three studies that have explored the genetic overlap between cannabis involvement and depression or suicide. Using a sample of adopted and non-adopted offspring, Marmorstein and colleagues (81) found that parental history of cannabis use disorder was associated, at a trend level, with major depressive disorder in non-adopted offspring even after accounting for offspring cannabis use disorder, indicating evidence for familial co-aggregation. Specifically examining their genetic overlap, Fu et al (82) noted that antisocial personality disorder was a complete mediator of the genetic overlap between cannabis use disorder and major depressive disorder in male twins. Finally, one study (83) has utilized the discordant twin design to explore whether the links between cannabis involvement, including early use and dependence,
