What is the General Health Questionnaire-12 assessing? Dimensionality and psychometric properties of the General Health Questionnaire-12 in a large scale German population sample.

Since the dimensionality and the related psychometric properties of the 12-item General Health Questionnaire (GHQ-12) are still under debate, the present study compares different factor solutions from the literature to determine which shows the best fit and to investigate reliability and construct validity. The analyses are based on a German population based representative sample (N=2,041), using face-to-face-interviews. The confirmatory factor analysis indicates the best fit to the one-factor model including response bias on the negative worded items according to Hankins. Thus, the importance of methodical aspects for the dimensionality was emphasized. Moreover, the correlations of the different subscales of the two- and three-factor models with several external criteria (BDI, PHQ-2, SF-36, PHQ-Anxiety, SPIN) do not substantially differ. The preferred unidimensional model shows good psychometric properties. According to its associations with the external criteria under study, the GHQ-12 as a unidimensional measure seems to be a useful screening tool for the assessment of mental distress or a minor psychiatric morbidity with a main focus on depressive symptomatology.