Factor analysis of the Zung Self-Rating Depression Scale in a large ambulatory oncology sample.

Screening cancer patients for depression with self-report inventories presents clinical and methodological challenges. Many investigators separate "somatic" from "cognitive" symptoms when adapting such measures to oncology settings. However, this practice has rarely been empirically validated through factor-analytic studies. The following study describes a factor analysis of the Zung Self-Rating Depression Scale (ZSDS) from a large ambulatory sample of cancer patients (N = 1,109). A four-factor solution emerged, consisting of a cognitive symptom factor, a manifest depressed mood factor, and two somatic factors (eating and non-eating related). These factors accounted for 20% (cognitive), 13% (mood), 8% (non-eating), and 7% (eating) of the variance on the Zung, respectively. The authors discuss the implications of these results as they pertain to screening cancer patients for depression.