Measuring health anxiety: moving past the dichotomous response option of the original Whiteley Index.

The Whiteley Index [WI; Pilowsky, I. (1967). Dimensions of hypochondriasis. British Journal of Psychiatry, 113, 89-93] is a widely used self-report measure of health anxiety, hypochondriasis, and illness phobia; however, the factor structure of the WI has proven unstable. Moreover, factorial investigations of the WI persist in the original true/false response format despite criticisms of dichotomous scales and the availability of a Likert scale version [Barsky, A. J., Cleary, P. D., Wyshak, G., Spitzer, R. L., Williams, J. B. W., & Klerman, G. L. (1992). A structured diagnostic interview for hypochondriasis: a proposed criterion standard. The Journal of Nervous and Mental Disease, 180, 20-27]. The current investigation explores the factor structure of the 5-point Likert scale version of the WI using a sample of 287 students (64 men, ages 18-34 [M=20.6; SD=3.2]; 223 women ages 18-45 [M=20.2; SD=3.2]) divided into two sex-matched groups. A 2-factor 8-item model was extracted from the first group using exploratory factor analysis. However, confirmatory factor analysis with the second group showed superior fit to the data using a precedent 2-factor 6-item model, demonstrating factorial invariance across response options. Comprehensive results, implications, and directions for future research are discussed.