Standardization of a screening instrument (PHQ-15) for somatization syndromes in the general population

BACKGROUND: The PHQ-15 is widely used as an open access screening instrument for somatization syndromes in different health care settings, thus far, normative data from the general population are not available. The objectives of the study were to generate normative data and to further investigate the construct validity of the PHQ-15 in the general population.

METHODS: Nationally representative face-to face household surveys were conducted in Germany between 2003 and 2008 (n=5,031). The survey questionnaires included, the 15-item somatization module from the Patient Health Questionnaire (PHQ-15), the 9-item depression module (PHQ-9), the Satisfaction With Life Scale (SWLS), the SF-12 for the measurement of health related quality of life, and demographic characteristics.

RESULTS: Normative data for the PHQ-15 were generated for both genders and different age levels including 5031 subjects (53.6% female) with a mean age (SD) of 48.9 (18.1) years. Somatization syndromes occured in 9.3% of the general population. Women had significantly higher mean (SD) scores compared with men [4.3 (4.1) vs. 3.4 (4.0)]. Intercorrelations with somatization were highest with depression, followed by the physical component summary scale of health related quality of life.

CONCLUSIONS: The normative data provide a framework for the interpretation and comparisons of somatization syndromes with other populations. Evidence supports reliability and validity of the PHQ-15 as a measure of somatization syndromes in the general population.