Physical anhedonia in Parkinson's disease

Anhedonia is the inability to experience physical or social pleasure. Its physical component is hypothesised to be due to dysfunction of a dopaminergic frontotemporal-subcortical circuit and has never been investigated as a possible affective complication of Parkinson's disease (PD). The aim of this study was to formally assess prevalence and correlates of physical anhedonia in PD patients compared with normal controls. Twenty five people with PD and 25 matched controls were administered a psychometric battery exploring mainly executive functions and mood. Hedonic tone was assessed using Chapman's Physical Anhedonia Scale. PD patients also underwent MRI linear measurement of frontal structures. Anhedonia levels were significantly higher in PD patients with respect to controls, although not extremely elevated; prevalence rate was 40% for parkinsonians, while no anhedonics were found among controls. Clinical, neuropsychological, and quantitative neuroradiological features did not show any significant correlation with physical anhedonia. Physical anhedonia appears to be a relatively frequent, although mild, affective disturbance of PD, independent from neurological, frontal, and depressive aspects.