Several longitudinal studies have investigated associations between conduct disorder and both cannabis use and problem cannabis use 4–8. A relatively consistent association between childhood conduct disorder and both these outcomes has been apparent in these investigations 9. Recent evidence suggests that conduct disorder is, itself, not a single phenomenon but rather comprises four distinct longitudinal phenotypes apparent between the ages of 4 and 13 years 10. Outcomes of conduct disorder might vary according to these phenotypes; however, this question has received limited attention with regard to subsequent cannabis use 4. Risk factors for conduct disorder, particularly early-onset persistent conduct disorder, have been found previously to include parental substance use and mental health problems, early-life social disadvantage and family adversity and childhood victimization 11. Adolescent cannabis use has also been shown to be associated with these early-life factors 12–13. This association could arise because these factors predispose to conduct disorder which, in turn, predisposes to substance use, or it might arise through other pathways including both other environmental influences and genetic factors shared between parents and offspring 12–13.
