Can the Whiteley Index be used to assess health anxiety in adolescents from the general population?

Health anxiety (HA) is characterized by worry about being or becoming ill. The Whiteley Index (WI) is a valid and frequently used measure for HA in adults. We examined item response distribution, floor and ceiling effects, and construct validity of four different one-factor models of the WI (an 8-item model, the widely used WI-7, a revised 7-item version (WI-7-R), and a 6-item version (WI-6-R)) in a population-based sample of adolescents, using data from the 16-17-year follow-up of the Copenhagen Child Cohort 2000 (N = 2521, 16-17 years old). Females generally scored higher on all eight WI items compared to males. Construct validity was examined by confirmatory factor analysis and hypothesis testing. The WI-7-R and WI-6-R both showed acceptable fits. All four models showed good internal consistency. Hypothesis testing showed good discriminant validity, as the hypotheses on positive correlations with anxiety, depression, and physical symptoms, as well as a negative correlation with health-related quality of life, were met for both the WI-7-R and WI-6-R. We advocate for the use of the WI-6-R, which focuses on core HA symptoms and excludes items concerning physical symptoms. The overall testing supports that the WI-6-R possesses valid psychometric properties for use with adolescents in the general population.