the pattern of results seen here. The mechanisms behind this are unknown but can be speculated about. For instance, in those adolescents who have non-delinquent peers, we would anticipate that the adolescents must have some other predisposition, i.e. a genetic risk for substance use. In other words, individuals who do not perceive their peers to be delinquent are less likely to use and develop dependence to drugs because of their peers’ behavior, for example, by peer encouragement, or social learning etc., and thus are more likely to display such vulnerability because of an underlying genetic predisposition. At the other extreme, the substance use among delinquent peers is likely to be rewarded and reinforced by environmental influences (hence the expression), but only after a certain point. This conclusion implies that the adolescents already have a genetic vulnerability; however, they only act upon this propensity in environments that do encourage negative behavior. This could happen for a number of reasons. For example, 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
