Predictive validity and clinical utility of DSM-5 Somatic Symptom Disorder — Comparison with DSM-IV somatoform disorders and additional criteria for consideration

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Abstract

Objective

Major changes to the diagnostic category of somatoform disorders are being proposed for DSM-5. The effect of e.g. the inclusion of psychological criteria (criterion B) on prevalence, predictive validity, and clinical utility of “Somatic Symptom Disorder” (SSD) remains unclear. A prospective study was conducted to compare current and new diagnostic approaches.

Methods

In a sample of N = 456 psychosomatic inpatients (61% female, mean age = 44.8 ± 10.4 years) diagnosed with somatoform, depressive and anxiety disorders, we investigated the current DSM-5 proposal (SSD) plus potential psychological criteria, somatic symptom severity, and health-related quality of life at admission and discharge.

Results

N = 259 patients were diagnosed with DSM-IV somatoform disorder (56.8%). With a threshold of 6 on the Whiteley Index to assess psychological criteria, the diagnosis of SSD was similarly frequent (51.8%, N = 230). However, SSD was a more frequent diagnosis when we employed the recommended threshold of one subcriterion of criterion B. Patients diagnosed with only SSD but not with DSM-IV somatoform disorder showed greater psychological impairment. Both diagnoses similarly predicted physical functioning at discharge. Bodily weakness and somatic and psychological attributions at admission were among significant predictors of physical functioning at discharge. Reduction of health anxiety, bodily weakness, and body scanning significantly predicted an improvement of physical functioning.

Conclusions

Psychological symptoms enhance predictive validity and clinical utility of DSM-5 Somatic Symptom Disorder compared to DSM-IV somatoform disorders. The SSD diagnosis identifies more psychologically impaired patients than its DSM-IV precursor. The currently suggested diagnostic threshold for criterion B might increase the disorder's prevalence.

Introduction

The diagnostic category of somatoform disorders is currently under revision for DSM-5 and ICD-11. The current diagnostic draft of DSM-5 Somatic symptom disorder [1; updated draft: April, 27th 2012] encompasses the former diagnoses of somatization disorder, undifferentiated somatoform disorder, pain disorder, and partly hypochondriasis. It introduces two major changes in comparison with DSM-IV: Firstly, the criterion A of somatic symptoms is no longer limited to medically unexplained symptoms, thus eliminating the contentious and unreliable distinction between medically explained and medically unexplained symptoms [2], [3] as well as an implicit mind–body dualism [4]. Secondly, positive psychological diagnostic criteria are added to the diagnosis in criterion B, which covers excessive thoughts, feelings, and behaviors related to these somatic symptoms or associated health concerns. At least one of the following must be present: 1) disproportionate and persistent thoughts about the seriousness of one's symptoms, 2) a persistently high level of anxiety about health or symptoms, and 3) excessive time and energy devoted to these symptoms or health concerns. Whereas earlier drafts of the diagnosis included a complex and a simple variant of SSD [5], with two of the psychological criteria required for the complex variant, the current draft suggests a specification of severity: mild = one B criterion fulfilled, moderate = 2 or more B criteria fulfilled, severe = 2 or more B criteria fulfilled plus multiple somatic symptoms. Criterion C pertains to chronicity and stipulates that the state of being symptomatic typically persist for more than 6 months. The consequences this definition of somatoform disorders might have on prevalence rates and on diagnostic validity of the disorder are still uncertain [4]. Given that in the current DSM-5 proposal, criterion A also includes medically explained symptoms, the role of valid psychological symptoms may be crucially important [6].

Numerous psychological symptoms of somatoform disorders have been investigated: An organic causal attribution has been suggested as a diagnostic criterion because of its possible predictive value regarding on clinical course and outcome. It is, therefore, assumed that the inclusion of this criterion will increase predictive validity and clinical utility [7], [8], [9], [10]. Although the etiology of the somatic symptoms is no longer relevant for the diagnosis, the criterion wording disproportionate and persistent thoughts about the seriousness of one's symptoms suggests that both a tendency to attribute symptoms to organic causes and a tendency towards catastrophizing will be common among diagnosed patients. The latter appears to be especially predictive of immediate and long-term outcome and its inclusion in the diagnostic criteria might, therefore, enhance predictive validity [7]. Findings also suggest that therapeutic modification of catastrophizing tendencies can improve treatment response [11].

Recently, evidence was found regarding the predictive relevance of health anxiety [12], [13], even though some studies have yielded contradictory results [11], [14], [15].

Symptom expectation and selective attention to bodily processes are generally understood to be part of the somatoform vicious circle [11], [16], [17]. One key example of this is frequent symptom checking which is not explicitly part of the draft of the SSD criteria. However, it might be implicitly subsumed under the broader category of non-specific excessive behaviors related to somatic symptoms or excessive time and energy devoted to the symptoms.

Given the proposed diagnostic changes, and in light of the fact that a broad variety of psychological characteristics appear to be associated with somatoform disorders [7], [9], [11], [18], further investigations are required to examine the merit of this evolving diagnosis. Specifically, studies are needed to test whether the currently proposed criterion B represents an optimal selection of psychological processes in order to increase the predictive validity and clinical utility of the diagnosis, which is a central goal of the DSM and ICD revisions [19]. Thus, in the present study, we aim to compare the frequencies of DSM-IV and DSM-5 somatoform-related diagnoses in a relevant clinical sample and to investigate which psychological features might enhance diagnostic validity. Employing a prospective design, we aim to measure potential psychological features at hospital admission and analyze their predictive validity and clinical utility regarding physical functioning at discharge.

Section snippets

Study design and subjects

In order to investigate the frequency and validity of currently proposed Somatic symptom disorder (SSD) we conducted a prospective diagnostic study in an inpatient sample at the psychosomatic hospital Schön Klinik Bad Bramstedt, one of the largest psychosomatic hospitals in Germany that focuses on cognitive-behavioral treatment of patients with disorders such as anxiety, depressive, and/or somatoform disorders. Treatment duration is usually 6 to 8 weeks. The study was approved by the Ethics

Sample

We invited n = 500 inpatients to take part in the study. Twenty patients declined, and 24 patients had to be excluded according to the exclusion criteria. The resulting sample consisted of 456 inpatients (participation rate, 91.2%). Patients' mean age at admission to the hospital was 44.5 years (SD = 10.4) with approximately 61% women. Out of all investigated patients, 94.5% (n = 431) suffered from a depressive disorder diagnosed by SCID-I and 56.1% (n = 256) from an anxiety disorder diagnosed by

Discussion

In our clinical inpatient sample, there was only a fair amount of agreement between the DSM-IV somatoform disorders and DSM-5 somatic symptom disorder. The new diagnosis identified patients who were younger and who reported more somatic, depressive, and anxiety symptoms. Yet, these patients were comparable regarding their self-reported physical disability. As suggested by the APA [4], we employed the Whiteley Index to assess criterion B. When we chose a cut-off score for its previously assessed

Conflict of interest

The authors have no competing interests to report.

Sources of funding

The study was conducted without external funding.

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