You could be reading the full-text of this article now if you...

If you have access to this article through your institution,
you can view this article in

Monitoring Depression Treatment Outcomes With the Patient Health Questionnaire-9

Löwe, Bernd MD, PhD*†; Unützer, Jürgen MD, MPH‡; Callahan, Christopher M. MD†; Perkins, Anthony J. MS†; Kroenke, Kurt MD†

Medical Care:
Original Article
Abstract

Background: Although effective treatment of depressed patients requires regular follow-up contacts and symptom monitoring, an efficient method for assessing treatment outcome is lacking. We investigated responsiveness to treatment, reproducibility, and minimal clinically important difference of the Patient Health Questionnaire-9 (PHQ-9), a standard instrument for diagnosing depression in primary care.

Methods: This study included 434 intervention subjects from the IMPACT study, a multisite treatment trial of late-life depression (63% female, mean age 71 years). Changes in PHQ-9 scores over the course of time were evaluated with respect to change scores of the SCL-20 depression scale as well as 2 independent structured diagnostic interviews for depression during a 6-month period. Test-retest reliability and minimal clinically important difference were assessed in 2 subgroups of patients who completed the PHQ-9 twice exactly 7 days apart.

Results: The PHQ-9 responsiveness as measured by effect size was significantly greater than the SCL-20 at 3 months (−1.3 versus −0.9) and equivalent at 6 months (−1.3 versus −1.2). With respect to structured diagnostic interviews, both the PHQ-9 and the SCL-20 change scores accurately discriminated patients with persistent major depression, partial remission, and full remission. Test-retest reliability of the PHQ-9 was excellent, and its minimal clinically important difference for individual change, estimated as 2 standard errors of measurement, was 5 points on the 0 to 27 point PHQ-9 scale.

Conclusions: Well-validated as a diagnostic measure, the PHQ-9 has now proven to be a responsive and reliable measure of depression treatment outcomes. Its responsiveness to treatment coupled with its brevity makes the PHQ-9 an attractive tool for gauging response to treatment in individual patient care as well as in clinical research.

Author Information

From the *Department of General Internal and Psychosomatic Medicine, Heidelberg University Medical Center, Heidelberg, Germany; the †Regenstrief Institute, Indiana University School of Medicine, Indianapolis, Indiana; and the ‡Department of Psychiatry & Behavioral Sciences, University of Washington School of Medicine, Seattle, Washington.

Supported by a research grant from the Max-Kade-Foundation, New York, to Dr. Löwe. The IMPACT study was supported by grants from the John A. Hartford Foundation, the California Health Care Foundation, the Hogg-Foundation, and the Robert Wood Johnson Foundation. The PHQ-9 was originally developed with an educational grant from Pfizer.

Reprints: Bernd Löwe, MD, PhD, Department of General Internal and Psychosomatic Medicine, Heidelberg University Medical Center, Im Neuenheimer Feld 410, D-69120 Heidelberg, Germany. E-mail: bernd.loewe@med.uni-heidelberg.de.

© 2004 Lippincott Williams & Wilkins, Inc.