The aim of this study was to assess the extent to which the association between CSA and early use of alcohol, cigarettes, and cannabis in adolescent girls is mediated by risk factors that cluster in families where CSA occurs. Given the challenge of measuring and statistically adjusting for the many risk factors associated with both CSA and early substance use, other approaches for attempting to isolate the effects of CSA on initiation of substance use were needed. In the current study, we modeled CSA as a predictor of initiation of alcohol, cigarette, and cannabis use (separately), then added co-twin early use status into models to control for genetic and shared environmental influences common to early use and co-occurring psychiatric and psychosocial risk factors (e.g., depression, physical abuse) The contribution of familial influences to the association between CSA and early use could be inferred by observing changes in the estimated risk attributed to CSA after adding co-twin early use status.
