Objective: This study evaluates the two-item Patient Health Questionnaire (PHQ-2) as a measure for diagnosing and monitoring depression.
Methods: We assessed construct validity in a cross-sectional sample of 1619 medical outpatients (mean age 43+/-14 years, 64% female) by comparing the PHQ-2 to four longer self-report questionnaires. Criterion validity was established in a subsample of 520 participants with reference to the Structured Clinical Interview for DSM-IV (SCID). Sensitivity to change was investigated in a prospective study of 167 patients who completed the SCID both at baseline and the 1-year follow-up.
Results: With reference to the SCID, the PHQ-2 had a sensitivity of 87% and a specificity of 78% for major depressive disorder and a sensitivity of 79% and a specificity of 86% for any depressive disorder. Its diagnostic performance was comparable with that of longer depression scales. PHQ-2 change scores accurately reflected improved, unchanged, and deteriorated depression outcomes.
Conclusion: The PHQ-2 performed favorably with respect to a standard diagnostic interview, as well as established depression scales and proved sensitive to change. Thus, the PHQ-2 appears promising as a brief multipurpose measure for detecting depression, grading its severity, and monitoring outcomes over time.