Prevalence and comorbidity of common mental disorders in primary care

Abstract

Objective

To estimate the prevalence and comorbidity of the most common mental disorders in primary care practice in Spain, using the Primary Care Evaluation of Mental Disorders (PRIME-MD) questionnaire.

Design

A systematic sample of 7936 adult primary care patients was recruited by 1925 general practitioners in a large cross-sectional national epidemiological study. The PRIME-MD was used to diagnose psychiatric disorders.

Setting

1356 primary care units proportionally distributed throughout the country.

Results

53.6% of the sample presented one or more psychiatric disorder. The most prevalent were affective (35.8%), anxiety (25.6%), and somatoform (28.8%) disorders. 30.3% of the patients had more than one current mental disorder. 11.5% presented comorbidity between affective, anxiety, and somatoform disorders.

Conclusions

The study provides further evidence of the high prevalence and high comorbidity of mental disorders in primary care. Given the large overlap between affective, anxiety and somatoform disorders, future diagnostic classifications should reconsider the current separation between these entities.

Introduction

The prevalence of mental disorders, their manifestations and their comorbidity are major issues in primary care. Mental disorders have a direct bearing on clinical practice and the planning of health resources. Increasingly, the responsibility for initial diagnosis of mental illnesses is falling on primary care units, the patient's first point of contact with the health system (Murphy et al., 2000).

One out of every three primary care patients presents clinical problems related to mental illness (Ormel et al., 1994, Kroenke et al., 1997) though the figures range from 26% to 60% (Ansseau et al., 2004, Baca et al., 1999, Spitzer et al., 1999, Norton et al., 2007, Jackson et al., 2001) even when using the same diagnostic instrument. In spite of the improvements in the clinical training of primary care physicians and the availability of screening assessment instruments for mental disorders, their diagnosis and treatment is still a major problem (Spitzer et al., 1999, Fernandez et al., 2007, Sartorius and Ustun, 1995). Indeed, in many patients consulting primary care physicians, mental health problems manifest themselves in the form of physical complaints rather than psychological or emotional ones (De Waal et al., 2009, De Waal et al., 2008, Löwe et al., 2008). The high rate of comorbidity between anxiety, depressive and somatoform disorders may well add to the confusion when the diagnosis is made (Mergl et al., 2007, Rush et al., 2005, Toft et al., 2005). The consequences of this situation for patients and the health system alike are evident: poor prognosis, high use of resources, and increased costs (Alonso et al., 2007, De Waal et al., 2004).

In response to these problems, efforts have been made to improve the early identification of patients. Epidemiological studies may contribute by defining the specific prevalence of various mental disorders in primary care. In some countries, studies have been conducted to identify their prevalence, distribution, and the most frequent forms of presentation. The studies published do not always apply the same methodology or the same assessment tools, and for this reason they are often difficult to compare.

It is important to have reliable, valid and brief instruments for use in this clinical context (Arroll et al., 2003). Instruments specifically designed for the evaluation of mental disorders in primary care, such as the Primary Care Evaluation of Mental Disorders (PRIME-MD), represent a major step forward in the detection and diagnosis of mental disorders (Spitzer et al., 1994). The PRIME-MD has been validated and used in various populations, with good results (Ansseau et al., 2004, Baca et al., 1999, Spitzer et al., 1999, Norton et al., 2007, Jackson et al., 2001, Loerch et al., 2000, Fraguas et al., 2006). It assesses the five most prevalent groups of disorders in primary care: depressive disorders, anxiety disorders, somatoform disorders, and alcohol- and eating-related disorders.

The aim of the present study was to estimate the prevalence of common psychiatric disorders and psychiatric comorbidity in a large sample of primary care patients. To our knowledge, this is the first nationwide, cross-sectional epidemiological study carried out in the primary care setting in Spain and the largest in a European country.