Thus, a potentially important difference of the current study is the relatively prolonged abstinence. In this cohort of SDI abstinence averaged 2.4 years for amphetamine and longer for other drugs. Reversible effects of drugs on brain structure have been well documented for alcohol. Recovery of brain volume as assessed with MRI methods in alcoholics can be measured within a few weeks and may last months after sobriety (13,23,12). Such recovery appears to be impeded by relapse (13,14,23). While similar studies of reversible tissue loss have not been performed for illicit drugs, PET neuroimaging studies in methamphetamine abusers show a reduction in dopamine transporter availability that reverses with prolonged abstinence (24). These temporal changes associated with cessation and relapse underscore the importance of studying long-term as well as short-term changes. Thus, the prolonged abstinence in our population could account for relatively specific changes in medial OFC and suggests the possibility that differences in medial OFC reflect more persistent, enduring brain changes.
