Objective: We evaluated the diagnostic validity of the 9-item depression module of the Patient Health Questionnaire-9 (PHQ-9) in elderly Korean patients and suggest an optimal cutoff score to screen for major depressive disorders.
Method: The PHQ-9 and an elderly health questionnaire were administered to 1060 subjects older than 60 years, chosen using a stratified random sample of the community. The PHQ-9 was measured and compared with the Geriatric Depression Scale, Center for Epidemiological Studies Depression Scale, and Beck Depression Inventory scores. Reliability and validity tests, factor analysis, and receiver operating characteristic curve analysis were performed.
Results: The PHQ-9 indicated that 175 subjects had depressive disorders, and 885 subjects were rated as healthy. The PHQ-9 showed significant positive internal consistency (r = 0.88) and test-retest reliability (r = 0.60). The convergent validity with Geriatric Depression Scale and Center for Epidemiological Studies Depression Scale was significantly positive (r = 0.74 and 0.66, respectively). We suggest a score of 5 as the optimal cutoff point when screening for depressive disorders using the PHQ-9.
Conclusions: The Korean version of the PHQ-9 is an appropriate diagnostic tool for depression, and a score of 5 is the optimal cutoff for Korean elderly subjects. Screening for depression in the elderly population using the PHQ-9 would be valuable when medically ill patients show depressive symptoms in a primary health care setting.