Cannabis use and mental health: a review of recent epidemiological research

Cannabis is the most commonly used drug in the world. This review examines recent epidemiological research on the relationships between cannabis use and mental health problems. Relationships with depression, anxiety disorders, mania and psychosis are examined, with relevant issues such as the effect of confounding variables, temporal directions and causality being discussed. Factors which influence the relationship such as dose-response effects, age of first cannabis use and risk of mental health problems are also examined. Causality is often difficult to establish, as cannabis is often used by those with mental illness for self-medication. However, there is substantial evidence to suggest that cannabis may induce or exacerbate a number of mental health problems.