Collectively, these findings provide strong evidence that P3AR reflects genetic risk prior to the expression of manifest SUDs. However, age appears to be an important moderator of this association. For instance, compared to older subjects, larger effect sizes are typically obtained among those younger than 18 (Polich, et al., 1994). In addition, mean levels change strikingly with development (Berman, et al., 2006; Carlson, et al., 2007; Hill, et al., 1999; Katsanis, Iacono, & McGue, 1996), dropping half a microvolt or more per year (Carlson, Iacono, & McGue, 2005). This reduction may reflect the influence of dopamine system genes (Berman, et al., 2006), possibly reflecting changes in the psychological or neural process involved.
