Medical News Today described a study reported in the British Journal of Psychiatry indicating that cannabis use in teens is associated with an increased risk of mental illness.
The link between marijuana use and psychosis is well-established. The March 2005 issue of Addiction published a 25-year longitudinal study that concluded that there is a causal link between cannabis use and later psychosis. In 2005, a study in the British Medical Journal found that cannabis users between 14 and 24 years were approximately 1.6 times more likely than non-users to report psychotic symptoms 4 years later. A study in Biological Psychiatry in May 2005 suggested that there was a genetic link predisposing some cannabis users to later psychosis.