Calibrating well-being, quality of life and common mental disorder items: psychometric epidemiology in public mental health research

BACKGROUND The assessment of 'general health and well-being' in public mental health research stimulates debates around relative merits of questionnaire instruments and their items. Little evidence regarding alignment or differential advantages of instruments or items has appeared to date. AIMS Population-based psychometric study of items employed in public mental health narratives. METHOD Multidimensional item response theory was applied to General Health Questionnaire (GHQ-12), Warwick-Edinburgh Mental Well-being Scale (WEMWBS) and EQ-5D items (Health Survey for England, 2010-2012; n = 19 290). RESULTS A bifactor model provided the best account of the data and showed that the GHQ-12 and WEMWBS items assess mainly the same construct. Only one item of the EQ-5D showed relevant overlap with this dimension (anxiety/depression). Findings were corroborated by comparisons with alternative models and cross-validation analyses. CONCLUSIONS The consequences of this lack of differentiation (GHQ-12 v. WEMWBS) for mental health and well-being narratives deserves discussion to enrich debates on priorities in public mental health and its assessment.