Patient Health Questionnaire (PHQ-SADS)

Abstract

The Patient Health Questionnaire Somatic Symptom Scale (PHQ-SADS), most commonly utilized in the form of the 15-item Somatic Symptom Scale (PHQ-15), is a highly efficient, self-administered instrument designed for rapid screening within primary care and general medical environments. Developed from the broader PRIME-MD assessment, the PHQ-15’s core function is to quantify the severity and subjective impact of common physical complaints, or somatic symptoms, over the preceding four weeks. By assessing how much patients are ‘bothered’ by these symptoms, the scale provides clinicians with crucial data to identify clinically significant distress, functional impairment, and potential underlying psychological conditions, thereby facilitating prompt diagnostic follow-up and targeted treatment planning in integrated health care settings.

Keywords

PHQ-SADS, PHQ-15, Somatic Symptom Severity, Screening Tool, Somatic Symptoms, Primary Care, Psychological Assessment, Functional Impairment, PRIME-MD

Authors

Kurt Kroenke, Robert L. Spitzer, Janet B. W. Williams

Purpose

The primary purpose of the PHQ-SADS, specifically its PHQ-15 component, is the reliable and rapid quantification of medically unexplained physical symptom severity. This instrument serves as an objective measure of somatic symptom burden, which is frequently observed to be highly correlated with underlying psychological distress, including significant depressive and anxiety disorders. The scale efficiently translates subjective physical complaints into a quantifiable score that aids clinical decision-making.

Designed for easy integration into busy outpatient clinics, the PHQ-15 allows for efficient tracking of symptom changes over time, making it valuable both for initial screening and ongoing outcome monitoring. Crucially, the assessment helps clinicians differentiate between routine symptom reporting and clinically significant somatic symptoms that warrant further clinical attention or evaluation for conditions such as Somatic Symptom Disorder, as defined by the latest DSM-5 criteria. It is a fundamental tool for enhancing integrated behavioral health services.</

Construct

The PHQ-SADS is primarily designed to measure the construct of Somatic Symptom Severity and its associated functional distress. Somatic symptoms, in this context, are physical manifestations that may or may not be fully explained by a conventional medical diagnosis but which nonetheless cause the patient significant concern, worry, or functional impairment. The 15 items comprehensively sample symptoms across various physiological domains, including pain (gastrointestinal, musculoskeletal, headache), cardiorespiratory concerns, and general constitutional symptoms (e.g., fatigue, sleep disturbance).

The intensity of this construct is assessed using a 4-point Likert scale (0 to 3) which specifically queries how much the patient has been “bothered” by each symptom during the past four weeks. This methodological focus moves beyond simply recording the presence or absence of a symptom, emphasizing instead the subjective impact and severity of the physical complaints. This approach is highly relevant to modern diagnostic frameworks for somatic symptom disorders, which prioritize distress and functional impairment over medical inexplicability.

Validity

The validity of the PHQ-15 component is robustly supported across extensive clinical research and trials. Criterion validity has been consistently demonstrated through strong concordance between PHQ-15 scores and diagnoses derived from rigorous structured diagnostic interviews, such as the full PRIME-MD, and established clinical diagnoses based on DSM-5 criteria for Somatic Symptom Disorder and related illnesses. The scale proves effective in accurately discriminating between patients who carry a significant somatic symptom burden and those who do not.

Furthermore, Construct validity is evidenced by the scale’s predictable and strong positive correlations with other standardized measures of psychological distress, including the PHQ-9 (for depression) and the GAD-7 (for anxiety), as well as inverse correlations with measures of functional status and quality of life (e.g., the SF-36). The instrument’s utility as an outcome measure is supported by its demonstrated sensitivity to change, showing improvement in scores following successful treatment for underlying psychological or somatic conditions.

Reliability

The PHQ-15 exhibits excellent psychometric reliability, specifically regarding internal consistency. Studies consistently report a high Cronbach’s alpha coefficient, typically falling within the range of 0.80 to 0.85. This strong internal consistency indicates that the 15 items reliably cohere and measure the same underlying construct of general somatic symptom severity, supporting the clinical practice of summing individual item scores to derive a total severity score.

In addition to internal consistency, Test-retest reliability for the PHQ-15 is also established as strong. This confirms that the scores obtained are stable and repeatable over short intervals when no significant clinical intervention or major life change has occurred. These reliability metrics collectively confirm the instrument’s capacity to provide consistent and dependable measurements of somatic symptom burden across diverse clinical and non-clinical populations.

Factor Analysis

Factor analytical studies conducted on the PHQ-15 predominantly support a parsimonious, dominant single-factor solution. This general factor is interpreted as representing overall Somatic Symptom Severity. The implication of this finding is that despite the physiological diversity of the 15 symptoms (ranging from pain to gastrointestinal complaints), they share a common underlying component, often related to generalized psychological distress, anxiety, or illness worry.

While some more complex analyses have occasionally identified minor secondary factors (such as groupings for pain-specific or vegetative symptoms), the overwhelming clinical and research consensus relies on the utility of the total summed score derived from the single-factor interpretation. This total score serves as a highly effective, overall indicator of the patient’s symptom burden and associated functional status.

Instrument

Test Type: Self-report screening questionnaire

Format: Paper-and-pencil or electronic administration; 15 items scored on a 4-point Likert scale (0 to 3)

Language Available: English, Spanish, German, and numerous other translations globally

Population Group: General patient population, especially those presenting in primary care settings

Age Group: Adolescents (typically 13 years and older) and Adults

Population Details: The PHQ-15 has been extensively validated across diverse clinical and non-clinical samples, confirming its broad applicability for screening common mental and physical health concerns and somatic symptom burden.

Test Methodology: Patients are instructed to rate how much they have been bothered by each of the 15 listed symptoms over the past four weeks. The numerical scores (0=Not bothered, 1=Bothered a little, 2=Bothered a lot, 3=Bothered a great deal) are summed to yield a total severity score, ranging from 0 to 45. This total score is then used to correlate with diagnostic likelihood and determine the required level of care.

Keywords

PHQ-15, Somatic Symptom Burden, Severity Index, Screening, PRIME-MD, Psychometrics, Pain Assessment, Patient Health Questionnaire, Chronic Pain

Authors

Author ORCID Identifier: N/A (Information typically not standardized for this early instrument)

Affiliation Email addresses: N/A (Contact generally routed through institutional licenses or official PHQ website)

Correspondence Address: Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA (reflecting the institutional affiliation of the primary authors)

Permissions & Fee and Test Year

The family of PHQ scales, including the PHQ-15 component, is generally considered to be in the public domain. They are available for use without charge for non-commercial clinical, research, and educational purposes worldwide. Formal permission may be required for large-scale commercial applications, proprietary modifications, or inclusion in commercial electronic health record systems. The scale was developed as part of the broader Patient Health Questionnaire initiative, formalized around 1999–2002, building directly upon the original PRIME-MD assessment tool introduced in 1994.

The original PDF linked in the source content can be downloaded here: http://www.healthplus-ny.org/data/bh_phq.pdf

Reference’s

• Kroenke, K., Spitzer, R. L., & Williams, J. B. W. (2002). The PHQ-15: Validity and utility of a brief measure for evaluating somatic symptoms. Psychosomatic Medicine, 64(3), 529-536.
• Spitzer, R. L., Kroenke, K., & Williams, J. B. (1999). Validation and utility of a self-report version of PRIME-MD: the PHQ primary care study. JAMA, 282(18), 1737-1744.
• The Patient Health Questionnaire (PHQ) and GAD-7 measures. Official Website.

Items of the Patient Health Questionnaire (PHQ-SADS)

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

This questionnaire is an important part of providing you with the best health care possible. Your answers will help in understanding problems that you may have. Please answer every question to the best of your ability.

0= Not bothered, 1= Bothered a little, 3= Bothered a lot

1. During the last4weeks, how much have you been bothered by any of the following problems?

1. Stomach pain………………………………………………..	1	2	3
2. Back pain……………………………….….………………..
3. Pain in your arms, legs, or joints (knees, hips, etc.)…….
4. Feeling tired or having little energy…………..…………
5. Trouble falling or staying asleep, or sleeping too much ……………
6. Menstrual cramps or other problems with your periods ……(women only)
7. Pain or problems during sexual intercourse………….
8. Headaches…………………………………..……………….
9. Chest pain………………………………….…………………
10. Dizziness..…………………………………..……………….
11. Fainting spells…………………………….…………………
12. Feeling your heart pound or race….……………………
13. 13. Shortness of breath…………………..……………………
14. Constipation, loose bowels, or diarrhea………………
15. Nausea, gas, or indigestion…………..…………………