Psychometric Properties of the Japanese CES-D, SDS, and PHQ-9 Depression Scales in University Students

We used an item response theory (IRT) model to simultaneously compare the psychometric properties of 3 commonly used self-report depression scales translated into Japanese-the Zung Self-Rating Depression Scale (SDS), the Center for Epidemiologic Studies Depression Scale (CES-D), and the Patient Health Questionnaire Depression Scale (PHQ-9)-in a Japanese university student sample. Although the 3 scales were likely to measure the same underlying construct-that is, depression-the choices of the negatively worded items in the SDS and CES-D did not function well. The CES-D provided more information than the other scales at the range of depression severity approximately from the mean through 2 standard deviations above the mean, while the PHQ-9 provided more information for the other degrees of depression. The PHQ-9 performed better as a whole, as it provided more information than the other scales on the broadest range of depression severity, and it did not contain items with inefficient choices. The CES-D may also be a good choice when sampling students with elevated levels of depressive symptoms. Finally, we linked the 3 instruments on a common scale using parameters derived from IRT analysis, and we provided a crosswalk table to enable the conversion of each scale score.