Introduction to the special issue on medically unexplained symptoms: background and future directions.

This special issue is devoted to the topic of medically unexplained symptoms (MUS), a heterogeneous group of conditions characterized by persistent physical symptoms that cannot be explained by medical illness or injury. Although psychological factors have long been regarded as central to these problems, patients with MUS have typically been managed within medical settings and referrals to mental health services have been relatively rare. In recent years, however, interest in the psychological nature and treatment of MUS has expanded, culminating in the development of tailored psychological interventions for these conditions. This, coupled with the increasing willingness of practitioners to diagnose conditions such as chronic fatigue syndrome, fibromyalgia and irritable bowel syndrome, has led to an increase in the number of patients who are referred for psychological treatment. At present, however, many psychological therapists are unfamiliar with the literature on MUS. With this in mind, this special issue presents a series of papers that provide an overview of what is known about the nature, aetiology and treatment of medically unexplained illness. This introductory paper provides general information about the clinical presentation, diagnosis, classification, terminology and epidemiology of MUS in adults, and concludes with an examination of important areas for future development in the field. Subsequent papers address the psychological mechanisms [Deary, V., Chalder, T., & Sharpe, M. (2007-this issue). The cognitive behavioural model of medically unexplained symptoms: A theoretical and empirical review. Clinical Psychology Review; Iverson, A., Chalder, T., & Wessely, S. (2007-this issue). Gulf war illness: Lessons from medically unexplained illness. Clinical Psychology Review; Rief, W., & Broadbent, E. (2007-this issue). Explaining medically unexplained symptoms: Models and mechanisms. Clinical Psychology Review; Roelofs, K., & Spinhoven, P. (2007-this issue). Trauma and medically unexplained symptoms: Towards an integration of cognitive and neuro-biological accounts. Clinical Psychology Review] and management [Deary, V., Chalder, T., & Sharpe, M. (2007-this issue). The cognitive behavioural model of medically unexplained symptoms: A theoretical and empirical review. Clinical Psychology Review] of these conditions. A separate overview of the literature on MUS in children and adolescents is provided by Eminson [Eminson, J. (2007-this issue). Medically unexplained symptoms in children and adolescents. Clinical Psychology Review].