As the preceding chapters have amply demonstrated, the search for answers to the questions raised by the existence and clinical importance of functional somatic syndromes has proceeded with increasing intensity and sophistication in the past decade. In addition to uncovering many individualizing dimensions of these syndromes, the research has also identified a number of methodologies that can be applied across the spectrum of these functional illnesses to investigate similarities and discrepancies. In this chapter, major research directions in the study of each of the nine syndromes are described and an attempt is made to highlight the following overlapping dimensions: biological markers of serotonergic responsivity in chronic fatigue syndrome and premenstrual syndrome; physical and psychological trauma in patients with fibromyalgia and irritable bowel syndrome; cognitive and sensory deficits of patients with premenstrual syndrome, multiple chemical sensitivity and repetitive strain injury; magnetic resonance and isotopic imaging and the psychological profiles of patients with temporomandibular joint dysfunction syndrome and atypical chest pain; biological dimensions, such as the genetic transmission of fibromyalgia and the experimental production of cellular abnormalities associated with interstitial cystitis. Finally, Gulf War illness is described, which has now been characterized as a collection of symptom-clusters overlapping with many of the functional somatic syndromes described in this volume.

Chronic fatigue syndrome: serotonergic responsivity; cognitive behavior therapy

The fact that a substantial proportion of chronic fatigue syndrome (CFS) patients have concurrent symptoms sufficient for a diagnosis of major depression has prompted the investigation of the serotonin function with the new method of d-fenfluramine challenge.