Anhedonia and its correlation with clinical aspects in Parkinson's disease

Anhedonia is one of the non-motor symptoms observed in the Parkinson's disease (PD). However, there is no clear relationship between anhedonia and its correlation with other symptoms of PD. The aim of this study is to evaluate the characteristics of anhedonia and its correlation with clinical aspects of PD in a relatively large cohort. We enrolled 318 patients with PD and 62 control subjects for this study. Patients and subjects were tested using the Snaith–Hamilton Pleasure Scale Japanese version and the Beck Depression Inventory 2nd edition for the assessment of anhedonia and depression. We also investigated the correlation among clinical aspects of PD, anhedonia, and depression in patients with PD. The Snaith–Hamilton Pleasure Scale Japanese version and the Beck Depression Inventory 2nd edition scores were significantly higher in patients with PD than in control subjects (p = 0.03 and p = 0.0006, respectively). All PD patients with anhedonia had a significantly higher score on the unified Parkinson's disease rating scale (UPDRS) parts I and II compared to PD patients without anhedonia. Additionally, all PD patients with depression scored significantly higher on UPDRS part I–IV than PD patients without depression. The patients with anhedonia and without depression had mild motor severity and their treatment was relatively low dosage. These results suggest that anhedonia and depression are slightly linked, but not the same. PD patients with only anhedonia may be closely linked apathy found in untreated early stages of PD.