Assessment of depression in patients with chronic fatigue syndrome.

Assessment of the relationship of depression to chronic fatigue syndrome (CFS) is a complicated but important topic. This relationship may range from the misdiagnostic (i.e., depression misidentified as CFS) to the etiologic (i.e., CFS causes an organic affective syndrome). Assessment should focus on the symptoms and syndromes of depressive disorder, utilization of a single rating scale to assess presumed depression is discouraged, and alternate approaches to classification that allow for symptomatic overlap of a major depressive disorder and CFS are suggested. Careful attention needs to be given to the use of external validating criteria in empiric studies, such as natural history, clinical course (including treatment response), and family history.