The utility of somatic items in the assessment of depression in patients with chronic pain - A comparison of the Zung Self-Rating Depression Scale and the Depression Anxiety Stress Scales in chronic pain and clinical and community samples

Objective: To investigate the role of somatic items in the assessment of depression in chronic pain. Methods: The Self-Rating Depression Scale was administered to 398 individuals with chronic pain, 313 psychology clinic patients with similar overall levels of depression, and a general population sample of 491. All three samples were also administered the Depression Anxiety Stress Scales. Results: Confirmatory factor analysis of pooled Self-Rating Depression Scale and Depression Anxiety Stress Scales items revealed that Self-Rating Depression Scale items denoting diurnal variation, decreased appetite, weight loss and constipation failed to contribute to depression in all 3 samples. Items denoting tachycardia and irritability also failed to discriminate between depression and a combined anxiety/stress factor in all 3 samples. The chronic pain sample endorsed somatic items, in particular psychomotor retardation, sleep disturbance, constipation, and fatigue, more strongly than the other samples relative to their endorsement of nonsomatic depression items. Conclusions: It was concluded that depression measures that give emphasis to somatic symptoms provide poor measures of depression severity in any individuals and in patients with chronic pain may lead to En overestimation of the severity of depression. More recently developed instruments avoid these limitations and are also better able to discriminate depression from related states such as anxiety and tension/stress.