Patient Health Questionnaire-15: Scoring, Cutoffs & Interpretation

01 - What it measures

What this scale measures.

The PHQ-15 is a 15-item self-report measure of somatic symptom burden. Patients rate how much they were bothered by common physical complaints - pain, gastrointestinal, cardiopulmonary and fatigue-related symptoms among them - over the past four weeks, from 0 (not bothered at all) to 2 (bothered a lot). Totals range 0-30, with scores of 5, 10 and 15 marking low, medium and high somatic symptom severity.

The scale counts symptom burden; it does not judge whether symptoms are medically explained. That neutrality is deliberate - high scores flag patients whose physical symptom load warrants attention regardless of cause, and in practice high PHQ-15 scores are associated with functional impairment, healthcare use and coexisting depression and anxiety. One item concerns menstrual problems, so men typically answer 14 of the 15 items.

02 - Origin & purpose

Where it comes from.

The PHQ-15 was described by Kroenke, Spitzer and Williams in 2002 as the somatic symptom module of the Patient Health Questionnaire, the self-administered family derived from the PRIME-MD system. It draws 13 items from the PHQ somatic module and adds the fatigue and sleep items from the depression module. Validation drew on around 6,000 patients from primary care and obstetrics-gynaecology clinics.

The purpose was a brief, self-administered severity measure for somatisation in busy medical settings, sitting alongside the PHQ-9 for depression and later the GAD-7 for anxiety, so that the three most common symptom domains in general medicine could be measured with one questionnaire family. It later served as the parent instrument for the abbreviated SSS-8 (Gierk et al. 2014).

03 - Scoring & cutoffs

How scoring works.

Each of the 15 symptoms is rated 0, 1 or 2 for the past four weeks, giving a total of 0-30. Kroenke and colleagues set cutpoints of 5, 10 and 15 for low, medium and high somatic symptom severity - the bands in the table below. The PHQ-15 is a severity measure, not a diagnostic test: a diagnosis of DSM-5 somatic symptom disorder additionally requires the psychological B criteria (excessive thoughts, feelings and behaviours related to the symptoms), which the PHQ-15 does not assess. For B-criteria measurement it is commonly paired with the SSD-12.

04 - Validation evidence

How well it performs.

In the original validation across roughly 6,000 primary-care and obstetrics-gynaecology patients, the PHQ-15 showed internal consistency of alpha 0.80, and rising scores tracked stepwise worsening in functional status, disability days and healthcare use (Kroenke et al. 2002). For detecting somatoform disorders in a high-risk primary-care population, van Ravesteijn et al. (2009) reported sensitivity of 78% and specificity of 71% against a diagnostic interview. German general-population norms come from Kocalevent et al. (2013, n = 5,031): mean scores were 4.3 for women and 3.4 for men, and somatisation syndromes occurred in about 9.3% of the population. Test-retest reliability is adequate in clinical samples, though weaker in healthy volunteers where symptom levels are low.

05 - How it compares

How it compares to the alternatives.

06 - When to use it

Right tool, wrong tool.

The PHQ-15 is a self-administered severity measure for somatic symptom burden across primary care, psychiatry and psychosomatic medicine.

It is not a diagnostic instrument for somatic symptom disorder. DSM-5 diagnosis requires the additional psychological B criteria, which the PHQ-15 does not capture; for that, pair it with the SSD-12. It also deliberately does not judge whether symptoms are medically explained.

07 - Confidence & precision

Reading the score with care.

No minimal clinically important difference has been formally established for the PHQ-15, and standard errors of measurement are not consistently reported across settings. Interpretation is therefore anchored on the fixed severity bands rather than on change scores: crossing from one band to another is more meaningful than a one- or two-point shift within a band. Test-retest stability is adequate in clinical populations but poor in low-scoring healthy samples, so small fluctuations near the bottom of the scale should not be read as change. Where fine-grained monitoring matters, combine the score with functional measures and clinical review rather than relying on the number alone.

08 - Limitations

What it cannot tell you.

- It counts symptoms without establishing cause; medical illness inflates scores, so results need clinical context. - It does not assess the DSM-5 B criteria, so it cannot diagnose somatic symptom disorder alone. - The four-week recall window limits sensitivity to rapid change. - The menstrual item means most men answer 14 items, complicating strict score comparability between sexes. - Sensitivity and specificity against diagnostic interviews are moderate (78%/71%), so it functions as a severity flag rather than a case-finder. - Norms are best established in German and US samples; local calibration may differ.

Common questions from clinicians

FAQ

References

Source literature.

1. [1]Kroenke K, Spitzer RL, Williams JBW The PHQ-15: validity of a new measure for evaluating the severity of somatic symptoms. Psychosomatic Medicine, 64(2), 258-266 (2002) ↩
2. [2]van Ravesteijn H, Wittkampf K, Lucassen P, et al. Detecting somatoform disorders in primary care with the PHQ-15. Annals of Family Medicine, 7(3), 232-238 (2009) ↩
3. [3]Kocalevent RD, Hinz A, Brahler E Standardization of a screening instrument (PHQ-15) for somatization syndromes in the general population. BMC Psychiatry, 13, 91 (2013) ↩
4. [4]Gierk B, Kohlmann S, Kroenke K, et al. The Somatic Symptom Scale-8 (SSS-8): a brief measure of somatic symptom burden. JAMA Internal Medicine, 174(3), 399-407 (2014) ↩