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, and depression as well as suicidal ideation and attempt are explained by individual-specific/causal factors. Even after accounting for covariates, such as childhood trauma exposure, use of cannabis prior to age 17 was associated with suicidal attempt (odds-ratio=3.49; but not with ideation or major depression). This association could not be equated to 1.0 even in genetically-identical/MZ twin pairs indicating that while shared genetic influences may be solely responsible for the association between early cannabis use and depression, potential causal or individual-specific non-causal factors played a role in the relationship between early cannabis use and suicidal attempt, over and above their shared genetic underpinnings.
