Depression affects Parkinson’s disease（PD）patient’s QOL. Although it changes with the diagnostic criteria used, the frequency of depression in PD is approximately 10‒30％. Anhedonia is characteristic in PD. According to research on anhedonia in PD using the Snaith‒Hamilton Pleasure Scale（SHAPS）, the positive ratio of anhedonia is high in PD. The SHAPS score significantly correlates with the severity of PD and duration of the disease. An examination of the literature on depression before the development of motor symptoms of PD revealed that the risk of PD is high in patients with a history of depression. Pathologically, the substantia nigra is affected in the later stages and raphe nuclei are affected in the early stages. This suggests that depression is a prodromal symptom of PD.