Screening for Depression Using Phq-2 : Changes Over Time in Conjunction with Mental Health Treatment

Objective: The two-item Patient Health Questionnaire (PHQ-2) meets the criteria for general screening of depression suggested by the U.S. Preventive Services Task Force. This study examined changes in the PHQ-2 over time, stratifying by receipt of mental health treatment, to help interpret screening results. Methods: We used nationally representative samples of the U.S. civilian, noninstitutionalized population from the 2004-2006 panels of the Medical Expenditure Panel Study. Adult respondents (n=23,770) completed the PHQ-2 twice, 10 months apart. Purchase of antidepressant medication and receipt of ambulatory mental health care were assessed for two four-month periods preceding PHQ-2 administrations. We categorized respondents as above or below the PHQ-2 threshold for probable depression and as receiving or not receiving mental health treatment. We examined changes in combined depression-treatment status over time using multinomial logistic regression. Results: At each time point, 83% scored below PHQ-2 depression threshold and had no mental health treatment; 8% scored below the threshold and reported some mental health treatment; 6% were above threshold but had no treatment, and 3% were above threshold and received some mental health treatment. Eighty-five percent remained in the same depression-treatment combination over time. In multivariate analysis, the strongest predictor of depression-treatment status at time 2 was status at time 1. Fifty-seven percent of those depressed and without treatment at Time 1 were not depressed at Time 2. Conclusions: The PHQ-2 is useful as a depression screener, with prevalence rates comparable to diagnostic interviews. The high proportion of remission without treatment complicates interpretation.
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