Regarding Hypothesis 3 (a low LR will predict AUDs but not SUDs), the first two tables also demonstrated a consistent relationship between a baseline low LR with the risk for AUDs, but LR was not related to the vulnerability toward SUDs. These findings underscore the heterogeneity among genetically-influenced characteristics that impact on the risk for AUDs and/or SUDs. The results are consistent with the literature indicating that some intermediate phenotypes (e.g., externalizing characteristics) relate to both AUD and SUD development (Schuckit, 2009; Slutske et al., 2002), while other characteristics, such as the low LR to alcohol and the skin flush associated with drinking, have been reported to be associated with the risk for AUDs alone (Eng et al., 2007; Schuckit, 2009; Schuckit and Smith, 1996, 2011).
