delinquent peers might be more likely to provide illicit substances, leading the vulnerable person to be more inclined to become dependent, whereas a person with fewer delinquent peers may be less likely to be offered illicit substances, and therefore, their genetic risk remains un-expressed. Thus, adolescents exposed to those with behavioral problems are more likely to have any underlying genetic risk for associated behaviors triggered. Our second aim was to examine how the association between PPD and DV changed with levels of PPD. Consistent with previous studies, there was a strong positive correlation between PPD and DV, demonstrating that exposure to peers one perceives to be delinquent does increase one’s risk for substance dependence in both male and female adolescents. The results also provide evidence that there is a significant genetic covariation between PPD and DV, and this covariation is not dependent on the levels of PPD. Therefore, the same genetic liability, and possibly genes, that drive the adolescents own vulnerability to substance dependence also contributed to either their choice of peers (selecting and attracting peers with similar characteristics to their own), their perception of their peers (those who are predisposed to substance dependence may also perceive their peers to
