(Compton et al., 2005; Kessler et al., 2001; Warner et al., 1995). In genetically informative data, SUD clusters with externalizing rather than internalizing behavior disorders (Kendler et al., 2007). This pertains to genetic connections (correlations) as well, and gives grounds to consider addiction an externalizing spectrum disorder (Iacono et al., 2008; Krueger et al., 2002). In other words, mechanisms of variation in CLA substantially overlap with those determining variation in social behavior. In effect, drug use behavior and its consequences comprise a facet and an indicator of social behavior, frequently engendered and sustained by the latter's earlier manifesting deviating forms, behavioral “gateways” to addiction.
