For FA and MD clusters that significantly predicted neuropsychological test scores (α=.05), hierarchical regressions examined mean FA/MD and substance use (i.e., lifetime marijuana use, marijuana use days per month, lifetime alcohol use, drinks per month) and their interaction as predictors of neuropsychological test score to determine whether the extent of substance use moderated the relationship between WM quality and neuropsychological performance in users (n=36). Further, to evaluate the potential influence of premorbid characteristics on neuropsychological performance, mean FA/MD and parental history of SUD were examined with regression analyses, where parental SUD was entered on step 1, average FA or MD of the significant cluster entered on step 2, and neuropsychological performance as the dependent variable.
