While we had hypothesized that the combination of multiple risk factors in the AE+ group would result in more severe deficits in the neuropsychological domain, as in recent behavioral studies (Graham, et al., 2012; Ware, O'Brien, et al., 2012), results revealed no significant differences between the AE+ and AE− groups on any neuropsychological measure. Thus, the presence of an ADHD diagnosis did not have the same impact in the exposed sample as it did in the non-exposed sample. The lack of exacerbated impairments suggests that different mechanisms or risk factors may underlie the behavioral and neuropsychological deficits in children with concomitant AE and ADHD. For example, neural changes resulting from prenatal alcohol exposure may lead to such severe impairment that the co-occurrence of changes associated with concomitant ADHD does not further exacerbate neuropsychological performance (Sonuga-Barke, 2005). Differences could also be due to methodological differences as the behavioral studies were based on parent report measures, whereas the current study assessed neuropsychological performance through direct standardized assessment measures. Possible differences between the groups in access to services, medication, and school placements also may have contributed to the discrepancy.
