Patient Health Questionnaire-15 (PHQ-15) Somatic Symptom Severity Scale

Abstract

The Patient Health Questionnaire Somatic Symptom Severity Scale (PHQ-15) is a brief, self-administered instrument developed in the mid-1990s as a component of the broader Patient Health Questionnaire (PHQ). The PHQ itself was derived from the clinician-administered Primary Care Evaluation of Mental Disorders (PRIME-MD). The PHQ-15 is specifically utilized to assess the severity of somatic symptoms and functions as an effective screening tool for potential somatization and somatoform disorders in adult populations. Based on the original DSM-IV criteria, this scale consists of 15 items that quantify the presence and level of bother caused by common physical complaints, such as dizziness or stomach pain, experienced over the preceding four weeks.

Scoring the PHQ-15 provides clear cut-off points for symptom severity: scores of 5, 10, and 15 correspond to low, medium, and high levels of somatic symptom severity, respectively. Research has demonstrated that the PHQ-15 possesses strong diagnostic validity and efficiency when compared to its predecessor, the PRIME-MD (Spitzer et al., 1999).

Keywords

PHQ-15, Patient Health Questionnaire, Somatic Symptoms, Somatization, Somatoform Disorders, Screening Tool, Primary Care, Symptom Severity, Mental Health.

Authors

Robert Spitzer, Janet Williams, Kurt Kroenke.

Purpose

The primary purpose of the PHQ-15 is to serve as a fast, self-administered screening tool for assessing the presence and severity of physical complaints that may indicate somatization or a broader somatoform disorder in clinical and occupational settings. By focusing on 15 core somatic symptoms, the instrument efficiently identifies individuals who may require further diagnostic evaluation by a clinician.

While the PHQ-15 was initially developed based on the criteria for somatoform disorders outlined in the DSM-IV, its utility remains relevant under the DSM-5 framework. The DSM-5 shifts emphasis from “medically unexplained symptoms” to the presence of distress and functional impairment caused by the somatic symptoms, which the PHQ-15 effectively measures through its severity scoring (Shih-Cheng et al., 2016). It is important to emphasize that the PHQ-15 is a screening tool, not a definitive diagnostic instrument.

Construct

The PHQ-15 measures the psychological construct of Somatic Symptom Severity. This construct encompasses the degree to which an individual is bothered by 15 specific physical symptoms over the past four weeks. These symptoms are those most commonly associated with somatoform disorders in primary care settings, including various pain complaints, gastrointestinal issues, and neurological symptoms (Kroenke et al., 2002).

Increased scores on the PHQ-15 are strongly correlated with negative clinical outcomes typically associated with somatization, such as heightened functional impairment, increased disability, and greater utilization of health care services (Changsu et al., 2009). The instrument is designed to capture the current level of symptom-related difficulty rather than focusing on historical symptoms, ensuring highly relevant and reliable data for immediate clinical action.

Validity

The PHQ-15 demonstrates robust psychometric validation across diverse populations, including clinical and occupational settings (De Vroege et al., 2012; Kroenke et al., 2010). Specific validation studies have confirmed its efficacy in various Asian populations, such as Korean and Chinese samples, though performance has been noted as suboptimal in Hispanic populations, possibly due to cultural variations in symptom identification and reporting (Interian et al., 2006).

Regarding screening efficacy, when utilizing a cut-off score of 6 or higher, the PHQ-15 exhibits a sensitivity of 78% (true positive rate) and a specificity of 71% (false negative rate) for detecting somatoform disorders. Crucially, the scale has a high negative predictive value of 97%, indicating that only a small minority of individuals scoring below 6 will likely meet criteria for a somatoform disorder (Van Ravesteijn et al., 2009). Furthermore, the instrument has demonstrated strong convergent validity, showing positive associations with established measures of psychological distress, such as the Beck Depression Inventory (BDI) and the General Health Questionnaire-12 (GHQ-12).

Reliability

The reliability of the PHQ-15 is considered acceptable for a rapid screening measure. Its internal consistency, which measures how well the items correlate with one another, is demonstrated by an acceptable Cronbach coefficient alpha of 0.80 (Kroenke et al., 2002).

Test-retest reliability, assessing consistency over a two-week interval, is reported as moderate, with an intraclass correlation coefficient of 0.83 (Van Ravesteijn et al., 2009). Importantly, research indicates that the reliability and validity of the PHQ-15 are generally stable and unaffected by common individual difference factors, including age, gender, and educational background (Kocalevent et al., 2013).

Factor Analysis

The PHQ-15 is structured to measure a single, overarching construct of somatic symptom severity, based on 15 core symptoms identified as highly prevalent in primary care patients with somatization. Although explicit details of the original exploratory or confirmatory factor analysis are often presented in the validation literature (Kroenke et al., 2002), the practical application supports a unidimensional model for screening purposes.

This unidimensional approach allows for easy interpretation of the total score as a direct measure of the overall burden of physical symptoms. Given the known high comorbidity between somatoform disorders and conditions such as anxiety and depressive disorders, the scale’s focus on somatic symptoms is particularly valuable in clinical settings where patients, especially those in East Asian cultures, may present with physical complaints rather than openly discussing underlying depressive or anxious feelings (Changsu et al., 2009).

Instrument

Test Type: Self-report screening questionnaire.

Format: 15 items utilizing a 3-point Likert-type scale to assess severity (“not bothered at all,” “bothered a little,” and “bothered a lot”).

Language Available: Translated into over 20 languages globally (Spritzer et al., 1994).

Population Group: General adult clinical and occupational populations.

Age Group: Adults.

Population Details: Validated across diverse samples, including those in primary care, occupational health, and specialized psychiatric outpatient settings.

Test Methodology: Respondents rate the severity of 15 somatic symptoms experienced over the past four weeks. Total scores range from 0 to 30. Cut-offs are 5 (low), 10 (medium), and 15 (high severity).

Keywords

PHQ-15, Psychometric Properties, Primary Care, Screening, Somatic Distress, Health Care Utilization, Diagnostic Validity, Internal Consistency, Cronbach’s Alpha.

Authors

Author ORCID Identifier: N/A (Information not provided in source).

Affiliation Email addresses: N/A (Information not provided in source).

Correspondence Address: Columbia University (Original affiliation).

Permissions & Fee and Test Year

The PHQ-15 is widely recognized as a public domain instrument and is generally considered free for use by clinicians and researchers. The scale was developed as part of the PHQ project originating in the mid-1990s, with the definitive validation study for the PHQ-15 published in 2002 (Kroenke et al.).

The scale’s accessibility and ease of use are major strengths, facilitating rapid integration into clinical workflow. However, users must be mindful that, as a self-report scale, the PHQ-15 is vulnerable to reporting biases; for instance, individuals with high neuroticism or negative affectivity may report inflated symptom scores (Watson et al., 1989).

The original PDF of the PHQ-15 can be downloaded here: http://www.phqscreeners.com/sites/g/files/g10016261/f/201412/English_0.pdf

Reference’s

• American Psychiatric Association (APA). (2013). Diagnostic and statistical manual of mental disorders: DSM-5. Washington, D.C: American Psychiatric Association.
• Spitzer, R., Williams, J., & Kroenke, K. (1994). Instructions for Patient Health Questionnaire (PHQ) and GAD-7 Measures (pp. 1-9). Retrieved from https://phqscreeners.pfizer.edrupalgardens.com/sites/g/files/g10016261/f/201412/instructions.pdf
• Spitzer, R., Kroenke, K., & Williams, J. (1999). Validation and Utility of a Self-report Version of PRIME-MD. The Patient Health Questionnaire Primary Care Study Group. JAMA, 282(18), 1737–1744. doi:10.1001/jama.282.18.1737
• Kroenke, K., Spitzer, R., & Williams, J. (2002). The PHQ-15: Validity of a New Measure for Evaluating the Severity of Somatic Symptoms. Psychosomatic Medicine, 64(2), 258-266. http://dx.doi.org/10.1097/00006842-200203000-00008
• Kroenke, K., Spitzer, R., Williams, J., & Löwe, B. (2010). The Patient Health Questionnaire Somatic, Anxiety, and Depressive Symptom Scales: a systematic review. General Hospital Psychiatry, 32(4), 345-359. http://dx.doi.org/10.1016/j.genhosppsych.2010.03.006
• Han, C., Pae, C., Patkar, A., Masand, P., Woong Kim, K., Joe, S., & Jung, I. (2009). Psychometric Properties of the Patient Health Questionnaire–15 (PHQ–15) for Measuring the Somatic Symptoms of Psychiatric Outpatients. Psychosomatics, 50(6), 580-585. http://dx.doi.org/10.1016/s0033-3182(09)70859-x
• Liao, S., Huang, W., Ma, H., Lee, M., Chen, T., Chen, I., & Gau, S. (2016). The relation between the patient health questionnaire-15 and DSM somatic diagnoses. BMC Psychiatry, 16(1). http://dx.doi.org/10.1186/s12888-016-1068-2
• Van Ravesteijn, H., Wittkampf, K., Lucassen, P., van de Lisdonk, E., van den Hoogen, H., & van Weert, H. et al. (2009). Detecting Somatoform Disorders in Primary Care With the PHQ-15. The Annals Of Family Medicine, 7(3), 232-238. http://dx.doi.org/10.1370/afm.985
• Interian, A., Allen, L., Gara, M., Escobar, J., & Díaz-Martínez, A. (2006). Somatic Complaints in Primary Care: Further Examining the Validity of the Patient Health Questionnaire (PHQ-15). Psychosomatics, 47(5), 392-398. http://dx.doi.org/10.1176/appi.psy.47.5.392
• Kocalevent, R., Hinz, A., & Brähler, E. (2013). Standardization of a screening instrument (PHQ-15) for somatization syndromes in the general population. BMC Psychiatry, 13(1). http://dx.doi.org/10.1186/1471-244x-13-91
• De Vroege, L., Hoedeman, R., Nuyen, J., Sijtsma, K., & van der Feltz-Cornelis, C. (2012). Erratum to: Validation of the PHQ-15 for Somatoform Disorder in the Occupational Health Care Setting. Journal Of Occupational Rehabilitation, 22(4), 590-590. http://dx.doi.org/10.1007/s10926-012-9383-z
• Watson, D., & Pennebaker, J. W. (1989). Health complaints, stress, and distress: Exploring the central role of negative affectivity. Psychological Review, 96, 234–254.

Items of the Patient Health Questionnaire Somatic Symptom Severity Scale (PHQ-15)

The PHQ-15 consists of 15 items asking respondents about the presence and severity of the following somatic symptoms within the last 4 weeks, rated on a scale of “not bothered at all,” “bothered a little,” and “bothered a lot.”

IMPORTANT: The following scale items must be preserved in their original language and must not be changed in any way.

• Stomach pain
• Back pain
• Pain in arms, legs, or joints (knees, hips, etc.)
• Headaches
• Chest pain
• Dizziness
• Fainting spells
• Feeling your heart pound or race (palpitations)
• Shortness of breath
• Constipation, loose bowels, or diarrhea
• Nausea, gas, or indigestion
• Feeling tired or having little energy
• Trouble sleeping
• Problems with sexual desire or performance
• Period pains or problems with periods (for women)