Neuropsychological Test Performances and Depression in Early-Stage De Novo Parkinson's Disease.

OBJECTIVE: Evaluate neuropsychological test performance in depressed patients with early-stage Parkinson's disease.

METHOD: Data from 422 participants from the Parkinson's Progression Marker Initiative were examined. The Geriatric Depression Scale-15 was used to categorize depressed and non-depressed participants. Neuropsychological tests measured verbal learning/memory, processing speed, visuospatial ability, verbal fluency, and working memory. Demographic and clinical variables were compared using independent samples t tests and chi-square analyses.Linear regression models were fit to adjust for age, years of education, and symptom duration.

RESULTS: The non-depressed group (n = 280) was significantly older; t(246.08) = 2.25, p = .026 and had higher education; t(420) = 2.35, p = .019; and longer duration of PD symptoms; t(170.58) = -2.13, p = .035 than the depressed group (n = 142). The non-depressed group performed better on a working memory task than the depressed group, t(420) = 2.05, p = .041, but the results did not appear to be of clinical significance. There was no significant difference between other cognitive domains. The results were not influenced by age, education, or disease duration.

CONCLUSIONS: Among patients with early-stage, untreated Parkinson's disease, depression does not appear to affect neuropsychological test performance. Clinicians should demonstrate caution in over-interpreting the influence of depression on cognition in this population.