Confirmatory factor analysis of the General Health Questionnaire (GHQ-12) in Spanish adolescents

Purpose To evaluate the factor structure of the 12-item General Health Questionnaire (GHQ-12) in a population of Spanish adolescents. Methods Cross-sectional study among 4,146 individuals (mean age 16.3 years). The students completed a health questionnaire that included the GHQ-12. A confirmatory factor analysis (CFA) was conducted with four factor structure models. Three of the models were theory-driven: unidimensional, two-dimensional (positive and negative questions), model proposed by Graetz (anxiety and depression, social dysfunction, loss of confidence); and the fourth model was based on our exploratory factor analysis (EFA). Results The Cronbach's alpha for internal consistency was 0.82. A three-dimensional structure was identified in the EFA. The first factor included items 1, 2, 5, 6, 7, and 9 of the GHQ-12; the second, items 3, 10, and 11; and the third, items 4, 8, and 12. The three factors together explained 53.7% of the variance. The model with the best fit in the CFA was the three-dimensional model proposed by Graetz, followed by the three-dimensional model derived from the EFA. These two models had acceptable goodness-of-fit indices. Conclusions In an adolescent population from Southern Europe, the GHQ-12 showed high internal consistency. The factor structure that best fitted the data was the Graetz three-dimensional model. However, the high correlations observed between factors suggest that the GHQ-12 should be used as a unidimensional scale, as currently done.