There are several limitations to this study. First, the sample size was modest (n=39) although in the range of similar studies. Second, subjects were dependent on multiple substances, precluding inferences about drug-specific effects on brain structure. Third, abstinence was based on self-report. SDI were remanded to residential treatment by the criminal justice system, either on diversion (instead of prison) or following a prison sentence, and before release to community probation. A minimum 2 months treatment compliance was required before they could participate in this study. Thus, the time in diversion or prison plus 2 months at ARTS resulted in relatively long abstinence. SDI were closely supervised and underwent frequent, observed urine drug tests. While self-report may be unreliable, it is highly unlikely that there were acute drug effects. Fourth, the findings of group differences and relationship between behavior and morphology are inconclusive about causality or predisposition. Finally, although a diagnosis of bipolar disorder was exclusionary, we did not specifically screen for major depression which has been shown to be associated with reduced OFC volume (38).
