Objective: The purpose of this study was to test the hypothesis that the patients with chronic fatigue who have the highest number of medically unexplained physical symptoms over their lifetime would also have the highest prevalence of current and lifetime affective and anxiety disorders, lifetime affective symptoms, and the most functional disability. A further goal was to use this information to modify the current case definition to better identify a subgroup of patients with chronic fatigue syndrome who are less likely to have psychiatric illness.
Design: Two hundred eighty-five consecutive patients with chronic fatigue were interviewed with the National Institute of Mental Health Diagnostic Interview Schedule and completed four self-rating questionnaires measuring psychologic distress, functional disability, and the tendency to amplify symptoms. Based on previously published data, patients were divided into four groups with a progressively higher number of lifetime medically unexplained physical symptoms. The prevalence of current and lifetime psychiatric disorders, lifetime psychologic symptoms, and extent of functional impairment was then compared in these four groups of patients.
Main results: The prevalence of current and lifetime psychiatric diagnosis and lifetime depressive symptoms increased linearly with the number of lifetime physical symptoms that the patient experienced. The extent of impairment in activities of daily living and the tendency to amplify symptoms also increased linearly with the number of medically unexplained physical symptoms.
Conclusion: The patients with the highest numbers of medically unexplained physical symptoms had extraordinarily high rates of current and lifetime psychiatric disorders. These data suggest that the current case definition for chronic fatigue syndrome inadvertently selects for patients with the highest prevalence of lifetime psychiatric diagnoses. A recommendation based on these results is to modify the case criteria for chronic fatigue syndrome to include patients with fatigue and few physical symptoms and to identify and consider excluding patients with high numbers of physical complaints.