Yahoo reports here:
Among more than 400 people in South London admitted to hospitals with a diagnosed psychotic episode, the study team found the heaviest smokers of high-potency cannabis averaged about six years younger than patients who had not been smoking pot. ... The researchers found that males were more likely overall to use cannabis and also had a younger age of onset of psychosis. The mean age at the time of the first psychotic episode for male users of cannabis was 26, and for female users was nearly 29. That compared with nearly 30 years old for male non-users and 32 for female non-users.
