Elsevier

General Hospital Psychiatry

Volume 30, Issue 3, May–June 2008, Pages 191-199
General Hospital Psychiatry

Psychiatry and Primary Care
Depression, anxiety and somatization in primary care: syndrome overlap and functional impairment

https://doi.org/10.1016/j.genhosppsych.2008.01.001Get rights and content

Abstract

Objective

To determine diagnostic overlap of depression, anxiety and somatization as well as their unique and overlapping contribution to functional impairment.

Method

Two thousand ninety-one consecutive primary care clinic patients participated in a multicenter cross-sectional survey in 15 primary care clinics in the United States (participation rate, 92%). Depression, anxiety, somatization and functional impairment were assessed using validated scales from the Patient Health Questionnaire (PHQ) (PHQ-8, eight-item depression module; GAD-7, seven-item Generalized Anxiety Disorder Scale; and PHQ-15, 15-item somatic symptom scale) and the Short-Form General Health Survey (SF-20). Multiple linear regression analyses were used to investigate unique and overlapping associations of depression, anxiety and somatization with functional impairment.

Results

In over 50% of cases, comorbidities existed between depression, anxiety and somatization. The contribution of the commonalities of depression, anxiety and somatization to functional impairment substantially exceeded the contribution of their independent parts. Nevertheless, depression, anxiety and somatization did have important and individual effects (i.e., separate from their overlap effect) on certain areas of functional impairment.

Conclusions

Given the large syndrome overlap, a potential consideration for future diagnostic classification would be to describe basic diagnostic criteria for a single overarching disorder and to optionally code additional diagnostic features that allow a more detailed classification into specific depressive, anxiety and somatoform subtypes.

Introduction

With prevalence rates around 10% each, depression, anxiety and somatization are the most frequent mental disorders in primary health care [1], [2], [3], [4]. Each of these disorders is associated with substantial functional impairment, increased disability days and elevated health care costs [5], [6], [7], [8], [9]. At least a third of patients with somatoform disorders have comorbid anxiety or depressive disorders, whereas depression and anxiety co-occur with one another up to 50% of the time [1], [5], [10], [11], [12], [13], [14]. Similarly, validated psychometric scales for depression, anxiety and somatization are highly intercorrelated [15], [16], [17]. The diagnostic overlap may be due in part to shared diagnostic criteria, such as sleep disturbances, loss of energy and impaired concentration [1,5,18]. In addition, treatment methods overlap in that antidepressants and cognitive–behavioral therapy are efficacious for depression, anxiety and somatization [19], [20], [21], [22]. Given these associations among the three syndromes and despite historical and recent assumptions to the contrary, there is little evidence that depression, anxiety and somatization are separated by natural boundaries [23]. Theoretical models, such as the tripartite model of anxiety and depression, were developed to describe the overlap of anxiety and depression [16], [21], [24], [25], whereas the relationship between somatization and the other two syndromes is less well studied [13], [26].

Naturally, the question regarding diagnostic overlap is highly relevant for the impending revisions of Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) and International Statistical Classification of Diseases and Related Health Problems, 10th Revision (ICD-10) [14], [18], [27]. Moreover, it is also important for diagnostic practice in primary care, in which specific anxiety or depressive disorders are recognized in only 10% to 60% of cases [28], [29]. To explore this issue, the description of comorbidities among these disorders is an important precondition. In addition, the depiction of the independent and overlapping contribution to different areas of functional impairment for each disorder can help to assess clinical utility of the diagnosis [23] and to determine whether the diagnostic conceptualization of depression, anxiety and somatization as separate conditions is justified in primary care medicine.

To investigate whether depression, anxiety and somatization reflect distinct diagnostic entities, our study addressed several aims. First, we determined the prevalence of these three syndromes, both individually and co-occurring. Second, we compared functional impairment in patients with severe levels of depression, anxiety and somatization compared to a reference group without these syndromes. Third, we evaluated the unique and overlapping contributions of depression, anxiety and somatization to several areas of functional impairment.

Section snippets

Patient sample

This study was part of the first phase of the Patient Health Questionnaire (PHQ) Anxiety Study that was conducted to develop a short self-administered measure for generalized anxiety disorder [4], [30], [31]. Patients were enrolled from a research network of 15 primary care sites located in 12 different states (13 family practice and 2 internal medicine) administered centrally by Clinvest, Inc. from November 2004 to June 2005. To minimize sampling bias, consecutive patients were approached at

Description of patients

The mean (S.D.) age of the 2091 primary care patients was 47.2 (15.4) years, with a range of 18–95; 66% were female, 81% were non-Hispanic White, 8% were African-American, 8% were Hispanic and 3% were other race/ethnicity. In terms of marital status, 64% were married; 22% were divorced, separated or widowed; and 14% were never married. Regarding education, 7% had not completed high school, 31% had a high school degree or equivalent, 36% had some college or an associate degree and 26% were

Discussion

The major finding from this large primary care study is that all areas of functional impairment are more strongly associated with the commonalities of depression, anxiety and somatization than by their independent contributions. In fact, the contribution of overlap of depression, anxiety and somatization to functional impairment greatly exceeded the unique contribution of each syndrome alone.

The substantial overlap among depression, anxiety and somatization may have several explanations. First,

Acknowledgments

We thank Beate Wild, Ph.D., and Mechthild Hartmann, M.A., Department of Psychosomatic and General Internal Medicine, University of Heidelberg, for their valuable comments regarding earlier drafts of the manuscript. Collection of data in this study was supported by an unrestricted educational grant from Pfizer, Inc., for the development of the GAD-7.

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