It is important to note that the differences in subcortical volumes in LTAA DAO vs. NSAC were numerically (but not statistically) smaller than the differences between STAA DAO and NSAC. The (numerically) smaller differences are consistent with either partial recovery of subcortical volumes with long-term abstinence or with selective survivorship (i.e., STAA with less subcortical volume loss are more likely to survive to long-term abstinence). These alternative hypotheses can only be decided between with an adequately powered longitudinal study. The lack of a statistically significant difference between subcortical volumes in STAA DAO and LTAA DAO is consistent either with no recovery of subcortical volumes with long-term abstinence or with inadequate power of the test of differences. Once again, this speaks to the need for adequately powered longitudinal studies.
