A second etiological pathway that emerged involved resiliency and externalizing behavior as a mediator in the association between SLC6A2 rs36021 and substance use. Those carrying the SLC6A2 rs36021 AA genotype were rated as having lower resiliency. This is not surprising given that SLC6A2 is critical in the fine tuning of the noradrenergic neurotransmission (Bönisch & Brüss, 2006) and the role that the noradrenergic system plays in the modulation of arousal, affective states, and stress reactions in challenging environments (Song, Jhung, Song, & Cheon, 2011; Wang, Xu, Gainetdinov, & Caron, 1999; Weischenker & Schroeder, 2007). In fact, prior work indicates that elevated noradrenergic signaling is related to increased susceptibility to psychological stress (Fitzgerald, 2013). In contrast to behavioral control, resiliency did not have a direct effect on substance use. This is consistent with prior work suggesting stronger effects of behavioral control compared to resiliency as a mediator of family SUD risk and substance abuse (Martel et al., 2009). However, lower resiliency was associated with higher rates of externalizing behavior, which then predicted increased rates of substance use. This is consistent with
