Cannabis Use and Its Association to Mental Illness: A Focus on Mood and Anxiety Disorders

Cannabis is the most commonly used illicit drug worldwide, and mental illnesses are among the most common group of medical disorders. There is strong evidence suggesting that cannabis use and mental illness highly cooccur. Cross-sectional data indicate an increased prevalence of cannabis use among individuals with mental illness, and an increased prevalence of mental illness among cannabis users. Notwithstanding, the majority of cannabis users do not suffer from concurrent mental illness, and vice versa. Longitudinal studies reveal conflicting results regarding the association between cannabis use and future incidence of mood and anxiety disorders. The inverse notion that mood and anxiety disorders are associated with initiation of cannabis use does not receive sufficient support in longitudinal studies. Cannabis use may have a negative effect on the course of mood and anxiety disorders. Additional research is required to explore possible causal associations between cannabis use and mood and anxiety disorders.