PHQ-15: When the Body Speaks What the Mind Can't — Somatic Symptom Assessment

Headaches. Stomach pain. Back pain. Dizziness. Fatigue that no amount of sleep resolves. Many patients present to mental health clinicians with physical symptoms that medical workups have failed to explain, or with physical symptoms that accompany and complicate their psychological distress.

The PHQ-15 (Patient Health Questionnaire, Somatic Symptom Severity Scale) provides a standardized way to assess and monitor these symptoms. It's a 15-item measure covering the somatic complaints most commonly seen in clinical settings, scored by severity over the past four weeks.

Why Somatic Symptoms Matter in Mental Health

The mind-body split in clinical practice is artificial and harmful. Psychological distress routinely manifests as physical symptoms, and physical symptoms routinely amplify psychological distress. Ignoring either side gives you an incomplete clinical picture.

Consider the numbers: approximately 50–75% of patients with depression report significant somatic symptoms. In some cultural contexts, somatic presentation is the primary way depression manifests. Anxiety disorders are inseparable from their physical components: palpitations, muscle tension, gastrointestinal distress. And somatization in its own right (persistent, distressing physical symptoms without adequate medical explanation) affects 5–7% of the general population.

The PHQ-15 captures this physical dimension of distress that the PHQ-9 and GAD-7 largely miss.

The 15 Symptoms

The PHQ-15 assesses bothersomeness (0 = not bothered at all, 1 = bothered a little, 2 = bothered a lot) for:

1. Stomach pain
2. Back pain
3. Pain in arms, legs, or joints
4. Menstrual cramps or problems (women)
5. Headaches
6. Chest pain
7. Dizziness
8. Fainting spells
9. Heart pounding or racing
10. Shortness of breath
11. Pain or problems during sexual intercourse
12. Constipation, loose bowels, or diarrhea
13. Nausea, gas, or indigestion
14. Feeling tired or having low energy
15. Trouble sleeping

Total scores range from 0 to 30.

Severity Interpretation

• 0–4: Minimal somatic symptom severity
• 5–9: Low severity
• 10–14: Medium severity
• 15–30: High severity

Scores of 10 and above are associated with significant functional impairment and healthcare utilization.

Clinical Applications

Thorough assessment alongside mood and anxiety measures. Administering the PHQ-15 alongside the PHQ-9 and GAD-7 gives you a three-dimensional view of your patient's distress: mood, worry, and body. This triad captures the full clinical picture far better than any single measure.

Identifying somatic amplification. Some patients experience normal physical sensations as intense, noxious, and alarming. High PHQ-15 scores relative to medical findings suggest somatic amplification, a cognitive-perceptual process that responds to psychological intervention (attention retraining, cognitive restructuring around body sensations, behavioral approaches to reduce body scanning).

Monitoring treatment response. If a patient's depression improves but their somatic symptoms persist, you've only addressed part of the problem. The PHQ-15 tracks whether physical symptoms are responding to treatment or whether they need specific attention.

Cultural sensitivity. In many cultural contexts, distress is expressed predominantly through physical symptoms rather than emotional vocabulary. The PHQ-15 meets the patient where they are, assessing the symptoms they're actually experiencing without requiring them to translate their suffering into psychological language.

Differentiating somatic depression. The PHQ-9 includes some somatic items (sleep, appetite, fatigue, psychomotor), but the PHQ-15 provides much more detailed somatic assessment. A patient scoring high on PHQ-9 somatic items and high on the PHQ-15 may have a different treatment trajectory than a patient with primarily cognitive depression symptoms. Somatic-predominant depression may respond differently to different antidepressants and may benefit from body-focused therapeutic approaches alongside cognitive work.

When to Be Cautious

The PHQ-15 is not a diagnostic instrument for medical conditions. High scores warrant consideration of medical evaluation when appropriate. The goal is not to dismiss physical symptoms as "just psychological" but to understand the interplay between physical and psychological distress.

Some items on the PHQ-15 (fatigue, sleep) overlap with depression symptoms. This is clinically meaningful rather than a measurement problem: it reflects the genuine overlap between somatic and depressive symptoms. But be aware that the PHQ-15 and PHQ-9 aren't fully independent measures.

Scores can be elevated by genuine medical conditions (chronic pain, autoimmune disorders, etc.). For patients with known medical conditions, the PHQ-15 is still useful: it tracks the subjective burden of physical symptoms, which is a valid treatment target regardless of etiology.

Discussing Somatic Symptoms Therapeutically

Many patients with prominent somatic symptoms have had frustrating medical experiences: repeated tests that find nothing, clinicians who imply the symptoms are imaginary, and a sense that no one takes their suffering seriously.

The PHQ-15 can help reframe this experience: "Your PHQ-15 score confirms that you're dealing with a significant physical symptom burden. These symptoms are real and they're affecting your quality of life. What I'd like to explore is how stress and emotional factors might be amplifying them, not causing them from nothing, but turning up the volume."

This framing validates the patient's experience while opening the door to psychological intervention. It's the difference between "it's all in your head" and "your brain and body are connected, and we can work with that connection."