Although our modeling was not exhaustive, we have demonstrated how genetic and environmental risks in CU and PGD are related. Until recently PGD was assumed to be an environmental (27) upstream risk factor for CU. The current data are not consistent with this hypothesis. Rather, the liability to affiliate with deviant peers was better explained by a combination of genetic and environmental factors for which CU could be understood as a causal “risk indicator”. This is consistent with a social or self selection process by which the genetic and environmental risks in CU largely underpin and drive the likelihood of affiliating with deviant peers.
