The impact of depressive symptoms in early Parkinson disease

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Abstract
Background: Depressive disorders may affect up to 50% of patients with Parkinson disease (PD) and are associated with increased disability and reduced quality of life. No previous study has systematically examined the impact of depressive symptoms in early, untreated PD. Methods: We administered the 15-item Geriatric Depression Scale (GDS-15) as part of two NIH-sponsored phase II clinical trials in PD, enrolling 413 early, untreated PD subjects. We used linear mixed models to examine the relationship of depressive symptoms, measured by the GDS-15, with motor function and activities of daily living (ADLs), as measured by the Unified PD Rating Scale (UPDRS). A time-dependent Cox model was used to examine the effect of demographic and clinical outcome measures as predictors of investigator-determined time to need for symptomatic therapy for PD. Results: A total of 114 (27.6%) subjects screened positive for depression during the average 14.6 months of follow-up. Forty percent of these subjects were neither treated with antidepressants nor referred for further psychiatric evaluation. Depression, as assessed by the GDS-15, was a significant predictor of more impairment in ADLs (p < 0.0001) and increased need for symptomatic therapy of PD (hazard ratio = 1.86; 95% CI 1.29, 2.68). Conclusions: Clinically important depressive symptoms are common in early Parkinson disease (PD), but are often not treated. Depressive symptoms are an important contributor to disability and the decision to start symptomatic therapy for motor-related impairment in early PD, highlighting the broad importance of identifying and treating depression in this population.