There is much current concern and publicity about the relationship between cannabis use and dependence, mental health, other drug use and related psychosocial outcomes, particularly among young people. While there is growing body of evidence suggesting a relationship, the nature of the relationship is complex and there are many methodological issues which may affect the conclusions that can be drawn. This study is a collaboration with investigators on the Victorian Adolescent Cohort study (renamed 2000 Stories). The following areas will be examined: 1) The relationship between cannabis and other drug use; 2)The natural history of cannabis use; 3)Cannabis use and mental health; and 4)Cannabis use and life transitions.