Follow-up analyses examined relationships between substance use variables and FA in regions that differed between groups. The range of alcohol use in both groups provided the opportunity to examine correlations between lifetime alcohol use and FA in the full sample (N = 72). Results revealed positive relationships in the three clusters where users had higher FA than controls (r = 0.30 to 0.33, P = 0.005 to 0.01), and negative relationships in regions where users had lower FA than controls (right and left crus cerebri, corpus callosum splenium, right inferior frontal gyrus, and left postcentral gyrus; r = -0.24 to -0.40, P = 0.0004 to 0.036).
