Age and cognitive impairment influence the performance of the General Health Questionnaire

The General Health Questionnaire (GHQ) is a screening instrument designed to detect nonpsychotic psychiatric disorders. Its discriminating ability can be influenced by factors such as the presence of physical illness, comorbidity with other psychiatric disorders, and the presence of cognitive impairment, which are more frequent in the elderly. The present study examines the influence of age and cognitive impairment on the performance of the GHQ-12, and was performed in the course of a family study designed to evaluate the risks for dementia, depression, and geriatric depression in the relatives of elderly subjects with dementia of Alzheimer type or major depression. Four hundred subjects who had completed the GHQ-12 were included. Test performance was evaluated by receiver-operating characteristic (ROC) analysis. Our results indicate that (1) the GHQ-12 is applicable to elderly subjects (<65 years), (2) its performance is comparable in different age groups, (3) the cutoff value for case identification is higher in the elderly (3/4) compared with younger individuals (1/2) and (4) mild cognitive impairment does not influence the good performance of the GHQ-12 in elderly subjects. In conclusion, our study verifies the usefulness of the GHQ-12 as an instrument to identify states of depression; this applies also to subjects with mild intellectual impairment. To optimize the discriminative ability of the questionnaire, we propose the use of different cutoff values for the GHQ-12 score for case identification depending on the age of each individual.