Against this general background, aims of this study were to conduct a new, large-scale epidemiological survey of a national sample of Australian twins, previously never interviewed, to collect detailed phenotypic information on patterns of cannabis use and cannabis-related symptomatology, associated use, abuse, and dependence on both licit and illicit drugs; psychiatric comorbidity including conduct disorder, MDD, social phobia, and panic disorder; child and family circumstances including opportunity to use drugs, exposure to interparental conflict, parenting practices, peer affiliations, and adult role transitions. Below we describe the methodology of this study and provide a series of results detailing:
