Validity of the Brief Patient Health Questionnaire Mood Scale (PHQ-9) in the General Population

Objective: The aim of this study was to assess the validity of the Patient Health Questionnaire depression module (PHQ-9). It has been subject to studies in medical settings, but its validity as a screening for depression in the general population is unknown.

Method: A representative population sample (2,066 subjects, 14-93 years) filled in the PHQ-9 for diagnosis [major depressive disorder, other depressive disorder, depression screen-positive (DS+) and depression screen-negative (DS-)] and other measures for distress (GHQ-12), depression (Brief-BDI) and subjective health perception (EuroQOL; SF-36).

Results: A prevalence rate of 9.2% of a current PHQ depressive disorder (major depression 3.8%, subthreshold other depressive disorder 5.4%) was identified. The two depression groups had higher Brief-BDI and GHQ-12 scores, and reported lower health status (EuroQOL) and health-related quality of life (SF-36) than did the DS- group (P's < .001). Strong associations between PHQ-9 depression severity and convergent variables were found (with BDI r = .73, with GHQ-12 r = .59).

Conclusion: The results support the construct validity of the PHQ depression scale, which seems to be a useful tool to recognize not only major depression but also subthreshold depressive disorder in the general population.