Development and psychometric validation of the Subthreshold Depression Screening Scale for Older Adults (StDSS-OA): a multiphase scale development study

Subthreshold depression is prevalent among older adults and is associated with impaired quality of life, functional decline, and increased risk of major depressive disorder. However, existing depression screening instruments mainly focus on depressive disorders and may not adequately capture the multidimensional characteristics of subthreshold depressive symptoms in older adults. This study aimed to develop and validate the Subthreshold Depression Screening Scale for Older Adults (StDSS-OA). A multiphase methodological study was conducted. The initial item pool was generated through literature review and qualitative interviews with older adults experiencing subthreshold depressive symptoms. Two rounds of Delphi expert consultation were conducted to refine the preliminary scale. A total of 354 older adults recruited from a nursing home in Jilin Province, China, were included for psychometric validation. Item analysis, exploratory factor analysis (EFA), confirmatory factor analysis (CFA), validity assessment, reliability analysis, and receiver operating characteristic (ROC) curve analysis were performed. The final StDSS-OA consisted of 19 items across five dimensions. EFA using principal axis factoring with Promax rotation supported a five-factor structure, explaining 61.969% of the total variance. Parallel analysis also supported the five-factor solution. CFA demonstrated satisfactory model fit (χ 2 /df = 1.642, RMSEA = 0.057, CFI = 0.977, TLI = 0.971, RMR = 0.043). The scale showed good content validity (S-CVI = 0.970) and internal consistency reliability (Cronbach’s α = 0.876). ROC analysis showed good discriminative performance relative to GDS-15-defined screening status. The StDSS-OA shows promising reliability and validity as a screening instrument for identifying older adults with elevated subthreshold depressive symptoms. It may support early identification and timely referral for further clinical assessment and appropriate intervention.