Hypersensitivity and hyperalgesia in somatoform pain disorders

Abstract

Objective: In psychiatry, pain disorders not explained by structural lesions have been classified for decades as somatoform pain disorders, the underlying concept being somatization. In a parallel move, somatic medicine has defined an expanding group of similar pain disorders, known as functional pain syndromes. Functional pain syndromes are characterized by enhanced pain sensitivity. The aim of our study was to investigate the proportion of patients with somatoform pain disorders who also meet the criteria of functional pain syndromes and the extent to which patients with somatoform pain disorders also show enhanced pain sensitivity.Methods: Data on pain sensitivity in 120 hospitalized patients were obtained by means of two algometric methods. The group of patients with somatoform pain disorders was further divided into two subsets: patients with and those without a co-diagnosis of a functional pain syndrome. Patients with nociceptive pain served as control group.Results: Of the 120 in-patients selected, 67 fulfilled the criteria of a somatoform pain disorder of which 41 (61%) also met the co-diagnosis of a functional pain syndrome. Patients with somatoform pain disorder differed from controls in that they showed enhanced pain sensitivity, irrespective of whether a functional pain syndrome was concomitantly present (p<0.001).Conclusions: Somatoform pain disorders show considerable overlap with functional pain syndromes, including enhanced pain sensitivity. This suggests the relevance of integrating somatosensory aspects of pain into a modified understanding of somatoform pain disorders. A C C E P T E D M A N U S C R I P TACCEPTED MANUSCRIPT 3 BackgroundFor decades, pain disorders not or not adequately explained by structural somatic injury (or any other physiological processes such as inflammation) have been classified as somatoform pain disorders especially if they occur in the context of depression, anxiety disorders, or psychosocial stress. Under the DSM-IV section on somatoform disorders, somatoform pain disorder is defined as "pain disorder associated with psychological factors" (307.80) [1]. In its definition of 'persistent somatoform pain disorder' (F45.40), ICD-10 even explicitly attributed a causal significance to the psychological factors [2]. The rationale of DSM-IV and ICD-10 in categorizing somatoform pain disorders relies on the traditional concept of somatization. In the psychoanalytical theory, somatization was conceived as an experience of "bodily symptoms" caused by (repressed) psychological distress. As a consequence, somatoform pain disorders were classified as "mental disorders". Patients, therefore, were referred to psychiatric care.In a parallel move, somatic medicine defined an increasing group of so-called functional somatic syndromes [3,4] or, more specifically functional pain syndromes [5]. In 1990, The American College of Rheumatology, for instance, recognized fibromyalgia as a clinical entity. For the first time, hyperalgesia (with respect to the tender points) was proposed ...

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