we found larger WM volumes in one-month abstinent PSU compared to both LD and one-month abstinent ALC. Our PSU cohort was dependent on alcohol (100%), cocaine (84%), and methamphetamine (21%). When the four PSU individuals with methamphetamine dependence were removed from the entire PSU sample, all WM volumes remained significantly larger compared to LD or ALC. This observation, together with the positive correlation of parietal WM volume with cocaine use quantities in the PSU suggests that, the larger WM volumes in our PSU cohort were not driven simply by methamphetamine dependence in the PSU group.
