Peer deviance is amongst the leading correlates of general externalizing psychopathology, including early onset of drug use – for instance, Lynskey and colleagues reported that vulnerability to substance use was strongly associated with self-reported affiliations with deviant peers (11). While peer affiliations are governed, in part, by the same heritable factors that influence substance use (49-51), they continue to play an environmental role in sustained drug involvement (52). While the role of peer affiliations may be viewed as tautological (i.e. we examine the characteristics of a population of drug using individuals by using population membership as a covariate), several studies report the independent effect of peers on drug use and externalizing psychopathology (53-57).
