Confirmatory factor analysis of the GHQ-12: can I see that again?

This paper reviews research relating to the factor analysis of the GHQ-12. We explore the question of whether there is a consistent replicable structure to the GHQ-12 using: (i) a comparative analysis of fit between identified factor models; and (ii) a confirmatory factor analysis of GHQ-12 data from our own study.

The factor models proposed from the literature were reviewed. The published factor loadings were used to carry out a factor matching analysis to identify similarities between the various factor models that have been identified. In addition, 490 patients visiting their general practitioner completed the General Health Questionnaire (GHQ-12) in the first phase of a longitudinal study evaluating service delivery to rural Tasmania. Three different methods for scoring the GHQ-12 were utilized and each resultant data set was analysed using a Confirmatory Factor Analysis (CFA) to establish which of the various factor models provided the most consistent description of the data.

None of the complete factor models that have been proposed have been consistently replicated across studies. Isolated factors were replicated between some studies but no single factor structure was replicated across all studies. All of the models had adequate fit to the Tasmanian data when the usual scoring was used. However, only one model had a consistently high 'goodness of fit' across scoring methods.

It was concluded that the 'best fit' was achieved by a model based on an early factor analytic study using an Australian sample. It was suggested that researchers wanting to extract scales from the GHQ-12 could use this model.