MR-based structural neuroimaging of individuals with different substance use disorders have yielded mixed findings regarding brain tissue volume alterations. Smaller WM volumes (or density), particularly of the frontal, temporal and cerebellar regions relative to drug-free controls were reported in middle-aged active and abstinent users of cocaine and cannabis (Lim et al., 2008; Matochik et al., 2005; Sim et al., 2007; Solowij et al., 2011). A few reports showed similar WM volumes (or density) in active or abstinent users of these substances compared to controls (Franklin et al., 2002; Hanlon et al., 2011; Liu et al., 1998). However, enlarged volumes or density of frontal, temporal, and subcortical WM were reported in active amphetamine users (Bartzokis et al., 2000; Thompson et al., 2004) and in amphetamine users in both early and long-term abstinence (Jernigan et al., 2005; Tobias et al., 2010). Here, 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
