Our study is limited in its capacity to test mechanisms, as discussed above. Early-onset persistent conduct problems might increase the risk of adverse adolescent outcomes through fostering relations with more deviant peers, alongside alienation from more conventional institutions and behavioural pathways. Maternal substance use could influence offspring substance use through the messages it conveys around the acceptability of certain behaviours. Shared genetic factors might also be important. Twin studies consistently suggest high heritability of cannabis use, although important specific genetic influences remain unidentified 37,38.
