PHQ-15 (Patient Health Questionnaire-15)

Foundational Context

Somatic symptoms — such as pain, fatigue, dizziness, and gastrointestinal discomfort — are among the most common reasons individuals seek medical care. Kroenke, Spitzer, and Williams (2002) formalized the PHQ-15 to provide a structured, reliable way to quantify these symptoms and examine their impact on functioning. The scale consolidates a wide range of physical complaints from the original PHQ, reflecting domains frequently encountered across medical and mental health settings.

The PHQ-15 is clinically valuable because somatic symptoms often coexist with anxiety disorders, depressive disorders, trauma-related conditions, and stress-related physiology. High scores may also indicate potential somatic symptom disorder or signal the need for multidisciplinary care. The scale supports efficient screening, fosters shared decision-making, and encourages a biopsychosocial approach to care.

What the Assessment Measures

The PHQ-15 captures the frequency and severity of common somatic symptoms, reflecting both patient distress and functional impact. Symptoms span multiple systems, including:

• Pain (back pain, headaches, limb pain)
• Gastrointestinal symptoms (nausea, constipation, bloating)
• Fatigue and low energy
• Shortness of breath
• Dizziness
• Sleep and menstrual-related concerns (if applicable)

By focusing on symptom burden rather than etiology, the PHQ-15 allows clinicians to identify patterns, track changes, and determine when further medical evaluation or integrated mental health support is appropriate.

Interpretation Guidelines

The PHQ-15 generates a total score (0–30) based on how much symptoms have bothered the respondent in the past four weeks.

Validated severity thresholds:

• 0–4: Minimal somatic symptoms
• 5–9: Low somatic symptom severity
• 10–14: Moderate somatic symptom severity
• 15+: High somatic symptom severity

Interpretation Notes:

• Higher scores indicate greater overall symptom burden, not a specific diagnosis.
• Moderate to high scores should prompt assessment of functional impairment, medical history, stressors, mood, anxiety, and trauma exposure.
• Somatic symptoms may be influenced by chronic illness, pain conditions, psychological factors, or lifestyle.
• Cultural differences can affect how physical symptoms are expressed or reported.
• The PHQ-15 should be interpreted alongside clinical judgment, patient history, and appropriate medical evaluation.

Psychometric Properties

Reliability

• Good internal consistency across diverse medical and psychiatric populations
• Stable measurement across repeated administrations during treatment

Validity

• Strong correlations with functional impairment, depression, and anxiety
• Demonstrated ability to identify individuals at risk for somatic symptom disorders
• Predictive of healthcare utilization, including frequent primary care visits
• Sensitivity to change, supporting its use for monitoring treatment response

Administration Considerations

• Best administered when exploring physical symptoms, especially when multiple complaints are present
• Useful for fostering discussion about mind–body connections, coping, and treatment planning
• Should be paired with clinical evaluation to determine whether symptoms require medical workup
• Helps differentiate between isolated physical symptoms and broader somatic patterns
• May support integrated behavioral health interventions when scores are moderate to high

Limitations

• Not diagnostic for somatic symptom disorder or any specific medical condition
• High scores can reflect medical illness, psychological distress, or both
• Self-report may be influenced by health literacy, cultural norms, or response style
• Does not assess symptom duration beyond the past four weeks