Validity and reliability of the Persian version of the Geriatric Depression Scale-15 in older adults with Parkinson's disease.

Objective: This study evaluated the validity and reliability of the Persian GDS-15 as a screening tool for depression in older adults with Parkinson's disease (PD), given its high prevalence and diagnostic challenges in this population.

Methods: This study included 160 older adults aged 65 years and above with a confirmed diagnosis of PD and 80 age-matched healthy controls. Participants completed the GDS-15, the depression subscale of the Hospital Anxiety and Depression Scale (HADS-D), and the Beck Depression Inventory-II (BDI-II). Data were analyzed using exploratory factor analysis (EFA), Confirmatory factor analysis (CFA), Cronbach's alpha, Intraclass Correlation Coefficient (ICC) (Test-retest reliability), and Pearson correlation coefficient. Additionally, receiver operating characteristic (ROC) curve analysis was performed to determine the optimal diagnostic cutoff score.

Results: Exploratory factor analysis revealed a three-factor structure for the Persian GDS-15, demonstrating excellent reliability (α = 0.94; ICC = 0.92). Strong convergent validity was evidenced by significant correlations with HADS-D and BDI-II (both p < 0.001). ROC analysis established an optimal cutoff of ≤5, showing outstanding diagnostic accuracy (sensitivity = 98.7%, specificity = 84.7%) for depression detection in PD.

Conclusion: The Persian version of the GDS-15 is a reliable and valid instrument for assessing depression in older adults with PD and can be utilized in both clinical and research settings.