Components of depression in Parkinson disease.

Depression is a clinically heterogeneous disorder common in Parkinson disease (PD). The goal of this study was to characterize PD depression in terms of components, including negative affect, apathy, and anhedonia. Ninety-five, nondemented individuals with idiopathic PD underwent a diagnostic interview and psychological battery. Twenty-seven patients (28%) met Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition [DSM-IV]) criteria for a current depressive episode. The best-fitting confirmatory factor analysis model had 3 factors (negative affect, apathy, and anhedonia). Apathy loaded most strongly onto a second-order factor representing global psychological disturbance. All factors are uniquely associated with depression status. Negative affect exhibited the strongest relationship. Psychological disturbance in PD is heterogeneous and can produce symptoms of apathy, anhedonia, and negative affect. Apathy appears to be the core neuropsychiatric feature of PD, whereas negative affect (eg, dysphoria) seems to be most pathognomonic of depression. Future studies should examine the specific neural correlates and treatment response patterns unique to these 3 components.