The mean age of the patients was 62.8 years (SD=11.3, range=46–82). The mean level of education was 11.3 years (SD=4.1). The median Montgomery-Åsberg Depression Rating Scale score was 12 (range=1–50). The mean MMSE score was 28.1 (SD=1.6). Twenty-two patients were right-handed. The mean age at onset of the first depressive episode was 33.4 years (SD=9.1); the median cumulative duration of the depressive episodes was 75 months (range=8–354).
We found significant negative correlations, after correction for intracranial volume, between depression duration and volumes of total cerebral gray matter (r=–0.66, df=16, p=0.003), frontal gray matter (r=–0.63, df=16, p=0.005), temporal gray matter (r=–0.71, df=16, p=0.001), and parietal gray matter (r=–0.64, df=16, p=0.004). When taking the gray matter/total brain volume ratios into account, the findings did not change. See F1 for a scatterplot of total cerebral gray matter data. Excluding the two right outliers did not change results (r=–0.71, df=14, p=0.002). No correlation with depression duration was found for any of the other MRI data. Depression duration was not significantly correlated with increasing age (r=0.26, df=17, p<0.24). The effects of depression duration remained significant, after adding age and intracranial volume to the regression analysis, for volumes of cerebral gray matter (regression coefficient [β]=–0.24, SE=0.09; t=–2.62, df=18, p<0.02), frontal gray matter (β=–0.08, SE=0.03; t=–2.32, df=18, p<0.04), temporal gray matter (β=–0.07, SE=0.02; t=–3.39, df=18, p=0.004), and parietal gray matter (β=–0.05, SE=0.02; t=–2.35, df=18, p<0.04).