Use of the Zung Self-Rating Depression Scale in cancer patients: feasibility as a screening tool

The feasibility, utility and reliability of the Zung Self-Rating Depression Scale (ZSDS) was examined in a large sample of ambulatory cancer patients. This tool and a brief 11-item version of the ZSDS (excluding nine items concerning somatic symptoms), which was developed during the course of the survey, were used to estimate the prevalence of self-reported depressive symptoms. Patient characteristics that may be associated with an increased risk of clinically significant depressive symptoms were also explored. Twenty-five ambulatory oncology clinics affiliated with Community Cancer Care, Inc. enrolled and surveyed 1109 subjects. The alpha coefficients for the ZSDS (0.84) and the Brief ZSDS (0.84) indicated high levels of internal consistency. The overall prevalence of clinically significant depressive symptoms as defined by the ZSDS was 35.9% and by the Brief ZSDS was 31.1%. The ZSDS and the Brief ZSDS were highly correlated (r = 0.92). The medical and demographic variables most associated with clinically significant depressive symptoms were more advanced stage of disease at time of diagnosis, lung cancer as primary tumor type, higher ECOG rating (greater degree of physical disability), and having been prescribed antidepressant medications. The high prevalence of depressive symptoms observed in this study is consistent with rates found in other studies of self-report depression instruments in cancer patients. The initial indicators of internal consistency and validity suggest that the Zung SDS or the brief version may be useful screening tools to identify depressive symptoms in oncology patients.