A confirmatory factor analysis of the 12-item General Health Questionnaire among older people.

BACKGROUND: the 12-item General Health Questionnaire (GHQ) is useful in measuring psychiatric morbidity in older people. Previous studies of its factor structure were often based on samples of young persons and on exploratory factor analysis techniques. The results varied from suggesting one to three factors.

METHODS: this study involved 2123 participants aged over 60 and 7490 younger adults in a population-based survey in Britain. It compared the relative plausibility of several factor structures proposed by previous researchers, as indicated by the Akaike's Information Criterion and the Non-Normed Fit Index. Correlation between factors and internal consistency were examined. Mean subscale scores by demographic characteristics were analysed by ANOVA for the best-fit model.

RESULTS: the 3-factor structure proposed by Graetz gave the best fit in both older and younger people. The properties of this model in older people were examined in details. The patterns of internal consistency and between-factor correlation were found satisfactory. Differences and similarities in subscale scores between demographic groups e.g. marital status, were presented.

CONCLUSION: the 12-item General Health Questionnaire may measure three aspects of mental health, namely Anxiety and Depression, Social Dysfunction, and Loss of Confidence.