to addiction, does not account for the risk for SUD. Supporting the role of phenotypic propensity in the risk for addiction, the transmissible liability index, TLI (Vanyukov et al., 2009, 2003a,b), a scale based on psychological indicators of CLA prior to exposure to drugs, was higher in boys who later developed cannabis use disorder compared to those who used cannabis but did not develop the disorder (Kirisci et al., 2009). It is noteworthy that no shared environment component (non-genetic sources of twins’ similarity) was detected for TLI in a twin study (Vanyukov et al., 2009). SUD or substance use has been used as an indicator of the highly heritable latent trait of disinhibition/externalizing (Clark et al., 2008; Iacono et al., 2008; Krueger et al., 2002; Young et al., 2000), supporting the role of behavior regulation/disinhibition as a developmental component of SUD liability (Tarter et al., 1999, 2003). Disinhibition, as indicated by hyperactivity, impulsiveness, antisociality/psychopathy, has long been hypothesized to be genetically related to substance abuse (e.g., Gorenstein and Newman, 1980).
