Depressive symptoms are measured by a 10-item subset of the 20-item Center for Epidemiologic Studies Depression scale (CES-D). The CES-D, which focuses on depressive symptoms experienced in the most recent week, was developed for use in epidemiological studies of general populations rather than for clinical diagnosis of depression [35]. The CES-D score in this analysis uses standard coding based on the number and severity of symptoms (range 0 to 30; high = more symptoms; Cronbach’s alpha = 0.83). The CES-D has demonstrated reliability in older populations [36]. Using clinical diagnosis of depression as the criterion, a 10-item form of the instrument showed good predictive ability among elderly Chinese [37].
