the body mass index (BMI) contributed significantly to the variances and therefore was the only used covariate. Neither age nor BMI was a significant predictor of subcortical tissue volume variance. Participants’ cigarette smoking status was not a significant predictor of any tissue volume; however, this exploration has to be treated with caution, as the proportion of smokers in the LD sample tended to be smaller than in the patient groups. Given our a priori hypotheses, all MANCOVAs of tissue volumes were followed-up with post-hoc analyses (to assess group differences for GM, WM, or CSF volumes) as well as pairwise and univariate t-tests (comparing LD, ALC and PSU). Also because of our a priori hypothesis, we did not correct for multiple comparisons. The reported p-values for GM are 1-tail, but those for WM and CSF volumes are 2-tail, because PSU unexpectedly had greater WM and smaller CSF volumes than LD and ALC. Although ALC and PSU did not differ significantly on the frequency of medical and psychiatric co-morbidities, these comorbidities were controlled for in all group comparisons. Effect sizes for pairwise comparisons were calculated using Cohen’s d (Cohen, 1988). Associations of the MRI outcome measures with measures of neurocognitive test performance
