To our knowledge, this is the first study to test the indirect effect of 5-HTTLPR on alcohol-related outcomes through level of response to alcohol. By using a relatively young sample (i.e., SRE-5 and parental monitoring were measured during the teenage years) and including only SRE items that pertain to the first five drinking occasions, we were able to capture a purer subjective response that was less likely to be confounded by acquired tolerance (Corbin et al., 2013; Morean & Corbin, 2008). We made this choice because there is evidence that acquired tolerance and early level of response (i.e., innate tolerance) are distinct (Higgins, Le, & Sellers, 1995; Morean & Corbin, 2008). Yet, one study found that participants with high tolerance were 2.8 times more likely to have the SS relative to the LL genotype (Turker et al., 1998), pointing to the possibility that acquired tolerance and early level of response are related. The extent to which these constructs are linked—and the nature of the possible mechanism that connects them—are interesting questions that should be addressed in future work.
