A hierarchy of distress: Mokken scaling of the GHQ-30.

BACKGROUND Hierarchical cumulative scales are common and informative in psychology. The General Health Questionnaire (GHQ) does not appear to have been subjected to an analysis that examines the hierarchical and cumulative nature of its items. We report an analysis of data from the 30-item GHQ (GHQ-30) as part of the Health and Lifestyle Survey (HALS). METHOD Data from 6317 participants who completed the GHQ-30 as part of the HALS were analysed using the Mokken Scaling Procedure (MSP), which is a computer program that searches polychotomous data for hierarchical and cumulative scales on the basis of a range of diagnostic criteria. RESULTS A final scale consisting of nine items from the GHQ-30 was obtained that, according to the criteria for a Mokken scale, was a reliable and very strong scale. The least difficult item in the scale is 'been (un)able to face up to your problems?' and the most difficult item is 'felt that life isn't worth living?' CONCLUSIONS Items from the GHQ-30 form a short hierarchical and cumulative scale. The majority of these items also appear in the GHQ-12. The nine-item GHQ shows better distribution properties than the GHQ-30 and compares very favourably with the GHQ-12.