Psychiatry and Primary CareThe Patient Health Questionnaire Somatic, Anxiety, and Depressive Symptom Scales: a systematic review
Introduction
The Primary Care Evaluation of Mental Disorders (PRIME-MD) was an instrument developed and validated in the early 1990s to efficiently diagnose five of the most common types of mental disorders presenting in medical populations: depressive, anxiety, somatoform, alcohol and eating disorders [1]. Patients first completed a one-page 27-item screener and, for those disorders for which they screened positive, were asked additional questions by the clinician using a structured interview guide. The latter was modelled after lengthier structured psychiatric interviews which were useful in research but impractical in clinical practice [2], [3], [4]. The PRIME-MD proved to have good operating characteristics and seemed reasonably efficient: it took an average of 5.6 min of clinician time to administer the PRIME-MD to patients without a mental disorder diagnosis and 11.4 min to patients with a diagnosis.
This modest investment of time was still a barrier to use given the competing demands in primary care where visits typically average 15 min or less and patients may have multiple acute and chronic medical disorders, preventive medicine needs and documentation requirements. Therefore, in two large studies enrolling 6000 patients (3000 from general internal medicine and family practice clinics and 3000 from obstetrics-gynecology clinics), a self-administered version of the PRIME-MD called the Patient Health Questionnaire (PHQ) was developed and validated [5], [6]. In the past decade, the PHQ in general and the PHQ-9 depression scale in particular have gained increasing use in both research and practice.
Given the popularity of the PHQ-9 for assessing and monitoring depression severity, a new seven-item anxiety scale using a response set similar to the PHQ-9 was initially developed to diagnose generalized anxiety disorder (GAD) (hence its name, the GAD-7) and validated in 2740 primary care patients [7]. Though originally developed to diagnose generalized anxiety disorder, the GAD-7 also proved to have good sensitivity and specificity as a screener for panic, social anxiety and post-traumatic stress disorder [8]. Finally, the PHQ-15 was derived from the original PHQ studies and is increasingly used to assess somatic symptom severity and the potential presence of somatization and somatoform disorders [9].
Each PHQ module can be used alone (e.g., the PHQ-9 if depression is the condition of interest), together with other modules or as part of the full PHQ. Although the PHQ was originally developed to detect five disorders, the depression, anxiety and somatoform modules (in that order) have turned out to be the most popular. Also, most primary care patients with depressive or anxiety disorders present with somatic complaints and co-occurrence of somatic, anxiety and depressive symptoms [the Somatic-Anxiety-Depressive (SAD) triad] is exceptionally common [10], [11], [12], [13], [14].
Thus, our article focuses on the PHQ-9 depression, GAD-7 anxiety, and PHQ-15 somatic symptom scales, drawing on data from both the original studies and other subsequent studies in the literature. We call this composite measure the Patient Health Questionnaire Somatic, Anxiety, and Depressive Symptom Scales (PHQ-SADS) (Appendix A). This review is particularly timely because of the large amount of clinical research published on the PHQ scales over the past decade, the frequent overlap of depressive, anxiety, and somatic symptoms, and the increasing emphasis as DSM-V develops to conduct dimensional as well as categorical assessments [15].
Section snippets
Literature search
We searched MEDLINE from 1999 through September 2009 using the following search terms: PRIME-MD, Patient Health Questionnaire, PHQ-9, PHQ-8, PHQ-2, GAD-7, PHQ-15. A total of 561 publications were identified, and the abstracts were reviewed (full bibliography is available upon request from the authors). Studies that gathered original data or that synthesized data from multiple studies as either a meta-analysis or a systematic review were retrieved and assessed for inclusion in our narrative
Overview of key validation studies
Together, the four original validation studies represented nearly 10,000 patients. Participants in the three primary care studies had a mean age of 46–55 years old; 60–69% were women, 8–30% were African-American and 4–9% were Hispanic [1], [5], [7]. Participants in the obstetrics-gynecology study had a mean age of 31; 100% were women, 15% were African-American and 39% were Hispanic [6]. Table 1 summarizes key psychometric characteristics of the PHQ-9, GAD-7 and PHQ-15. In addition to the four
Diagnostic performance and psychometric characteristics
The PHQ-9 can be used either as a diagnostic algorithm to make a probable diagnosis of major depressive disorder (MDD) or as a continuous measure with scores ranging from 0 to 27 and cutpoints of 5, 10, 15 and 20 representing mild, moderate, moderately severe and severe levels of depressive symptoms. MDD should be considered in patients who endorse ≥5 of the 9 symptoms as present “more than half the days” (the 9th item counts if endorsed “several days”) and one of the first two symptoms
Original PHQ anxiety module
The original PHQ anxiety module focused on two diagnoses: panic disorder and other anxiety disorder. The 15-item panic module yielded a probable diagnosis of panic disorder for individuals who answered “yes” to the first four questions and endorsed ≥4 of 11 somatic symptoms during an anxiety attack. In addition to validation in the two original PHQ studies, further research has strengthened the evidence for the panic disorder section [89], [121], [122], [123], [124], [125]. The other anxiety
Three limitations in the classification of somatoform disorders
Three findings from recent research regarding the classification of somatoform disorders is relevant to the PHQ-15 [132], [133]. First, fewer chronic symptoms are probably needed than has traditionally been required for the diagnosis of somatization disorder which captures less than 10–20% of the patients with chronic and disabling somatization in primary care. Second, focusing primarily on current rather than lifetime symptom counts may be desirable due to the greater reliability and
Overlap and additive effects
The comorbidity of somatic, anxiety and depressive symptoms (the “SAD” triad) is well-established [12], [13]. Three recent large epidemiologic studies in primary care confirm that “pure” forms are much less common than overlapping syndromes; most patients reporting high levels of one symptom type also report high levels of one or both of the other types of symptoms [14], [154], [160]. Also, somatic, anxiety and depressive symptoms have independent, additive and differential effects on multiple
Conclusion
While we have summarized the salient PHQ data, a comprehensive comparison of the PHQ with all alternative scales is beyond the scope of this review. Evidence-based literature syntheses of depression measures have recently been published [21], [166]. Another limitation is the uncertain efficacy of screening for mental disorders on outcomes. For example, it appears that depression screening alone may not be sufficient to improve patient outcomes [169]. On the other hand, there is substantial
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Recent epidemiologic studies have found that most patients with mental illness are seen exclusively in primary care medicine. These patients often present with medically unexplained somatic symptoms and utilize at least twice as many health care visits as controls. There has been an exponential growth in studies in this interface between primary care and psychiatry in the last 10 years. This special section, edited by Jürgen Unutzer, M.D., will publish informative research articles that address primary care-psychiatric issues.