Modeling the PHQ-15: The factor structure of somatic symptoms in a large community sample

The Patient Health Questionnaire-15 (PHQ-15) is widely used to assess somatic symptom burden, but its latent structure remains uncertain. This study tested competing PHQ-15 factor models and their associations with demographic and psychological variables in a large, nationally representative UK sample (N = 1405). Confirmatory factor analyzes using WLSMV evaluated alternative structures reported in the literature. Several multifactor models showed acceptable fit, but a four-factor model comprising pain, cardiopulmonary, gastrointestinal, and fatigue domains provided the best overall fit and outperformed a one-factor solution. Inter-factor correlations were high, indicating substantial overlap between domains and supporting the utility of the total PHQ-15 score. Males reported slightly lower symptom burdens, and younger adults reported more somatic complaints. Findings support multidimensionality alongside a strong general somatic distress tendency, though the PHQ-15 does not fully align with ICD-11 bodily distress disorder criteria.