Structural validity of the 5-item World Health Organization Well-being Index (WHO-5) in patients with schizophrenia spectrum disorders

Abstract

BackgroundWhen monitoring the severity and impact of schizophrenia spectrum disorders, a measure of subjective well-being should ideally accompany measures of symptom severity and medication side effects. The self-reported 5-item World Health Organization Well-being Index (WHO-5) is a brief, generic, and widely used measure of subjective well-being. However, the structural validity of the WHO-5, namely, whether the individual item scores can be combined to produce a meaningful total score, has not been examined among patients with schizophrenia spectrum disorders. MethodUtilizing data from 399 Danish patients with schizophrenia spectrum disorders attending the Psychiatric Services of the Central Denmark Region, we employed Rasch analysis to examine the structural validity (i.e., unidimensionality, overall fit to the Rasch model, and differential item functioning) of the WHO-5. ResultsThe WHO-5 was found to be unidimensional with no differential item functioning for age, sex, or inpatient/outpatient status. However, in the initial analysis, some misfit to the Rasch model, partially caused by the disordering of response categories, was evident. In adjusted analyses in which the item response categories 2 (Less than half of the time) and 3 (More than half of the time) were merged, overall fit to the model was improved. ConclusionsWhen two item response categories were merged, the Danish version of the WHO-5 was found to be structurally valid for patients with schizophrenia spectrum disorders. This suggests that the WHO-5 holds promise as a measure of subjective well-being in this patient population.