Parenting behavior, sibling and peer influences have been shown to be associated with greater risk of adolescent and young adult alcohol (Barnow et al., 2002) and drug abuse/dependence, both alone (Scherrer et al., 2008; Duncan et al., 1996) and comorbid with depression (Martin et al., 2004), anxiety (Lindhout et al., 2009) and conduct disorder (Webster-Stratton and Hammond, 1999). However, the existing literature has not demonstrated that these parenting and peer influences are significantly associated with comorbidity after accounting for familial vulnerability. In addition, the magnitude of familial contributions, parenting and peer influences may vary by patterns of comorbidity. For example, these influences may differ in their association with alcohol abuse/dependence that is comorbid with depression as compared to marijuana abuse/dependence comorbid with conduct disorder.
