Depressive symptoms in Parkinson's disease are related to decreased hippocampus and amygdala volume.

Depression and anxiety are common in Parkinson's disease (PD), and are among the non-motor symptoms that interfere with quality of life dramatically. Motor, cognitive, and affective features overlap in PD, hampering diagnosis. To shed more light on the contribution of structural brain changes to the presence of PD-related depressive symptoms, we conducted a Voxel-Based Morphometry (VBM) study. We hypothesized that depressive symptoms in PD are related to regional gray matter (GM) volume loss within the limbic circuit. We analyzed the T1-weigthed magnetic resonance imaging (MRI) images of 67 PD patients with a mean disease duration of 2.95 (±3.39) years. Scores on the Beck Depression Inventory (BDI) and GM probability maps were analyzed by regression analysis to study the association between GM volume and severity of depressive symptoms. Results are reported at both the uncorrected and the family-wise error (FWE) corrected level for multiple comparisons. The BDI scores correlated negatively with bilateral hippocampus and right amygdala volume and positively with the volume of the anterior cingulate cortex. These findings confirm the hypothesized involvement of the limbic circuit in PD-related depressive symptoms. We speculate that non-dopaminergic changes are essential in the pathophysiology of depressive symptoms in PD, because our findings suggest the involvement of extra-striatal brain regions.