This chapter considers three groups, medically unexplained symptoms, somatoform disorders, and functional somatic syndromes. Describing the nature of these groups, it talks about their prevalence in cross-sectional studies in primary, secondary care and population-based studies. Medically unexplained symptoms are very common both in the general population and in primary and secondary care, but at least in the first two settings most are transient. Systematic reviews of the prevalence of irritable bowel syndrome in population-based samples have indicated that the prevalence varies considerably with the definition of the syndrome. Functional somatic syndromes are also common but only some patients with these syndromes also have numerous somatic symptoms. There is little doubt that somatoform disorders, or bodily distress syndromes, are an important and challenging group of conditions that are expensive in terms of healthcare use and time missed from work.

This chapter discusses the terminology, stressing the difficulties of the words and concept of medically unexplained symptoms (MUS), and discussing the pros and cons of alternative terms. A fundamental problem with the concept underlying medically unexplained symptoms is the dualism it fosters. The chapter provides the empirical foundation of positive psychobehavioural descriptors, and refers to their suitability as diagnostic criteria in more detail. It has been shown that patients with chronic unexplained symptoms report a negative self-concept of being weak, not tolerating stress and not tolerating any physical challenges. Avoidance of physical activities was the most powerful discriminator between patients with somatic complaints needing medical help and feeling disabled, and those with somatic complaints but without healthcare needs or disability. An important conceptual issue concerns the influence on classification of the psychophysiological models for the experience of disabling bodily symptoms.

This chapter provides an overview of the current state of evidence regarding treatment of medically unexplained symptoms, somatisation and the functional somatic syndromes. Both primary and secondary care studies have been performed to assess the efficacy of psychological interventions, most commonly cognitive behaviour therapy administered by a mental health professional, or antidepressants, prescribed by the patient's usual doctor. Thirteen trials evaluated cognitive behaviour therapy, five evaluated antidepressants, four the effect of a consultation letter to the general practitioner (GP) and three the training of GPs. The chapter reviews psychological treatments and the use of antidepressants. It uses three systematic reviews to provide an overview of the evidence of efficacy of interventions for functional somatic symptoms. The evidence is stronger for some pharmacological treatments than for psychological treatments partly because of the universal use of placebo tablets and the lack of an attention-placebo in psychological treatment trials.