Dimensional, categorical, or dimensional-categories: testing the latent structure of anxiety sensitivity among adults using factor-mixture modeling.

The present study tested multiple, competing latent structural models of anxiety sensitivity (AS), as measured by the Anxiety Sensitivity Index-3 (ASI-3; Taylor et al., 2007). Data were collected from 3 sites in North America (N=634). Participants were predominantly university students (M=21.3 years, SD=5.4). ASI-3 data were evaluated using an integration of mixture modeling and confirmatory factor analysis-factor mixture modeling (FMM; Muthén, 2008). Results supported a 2-class 3-factor partially invariant model of AS. Specifically, the FMM analyses indicated that AS is a taxonic (two-class) variable, and that each categorical class has a unique multidimensional factor structure. Consistent with the specific point-prediction regarding the hypothesized parameters of the putative latent class variable, FMM indicated that the putatively "high-risk" subgroup of cases or latent form of AS composed approximately 12% of the studied sample whereas the putatively "normative" subgroup of cases or latent form of AS composed 88% of the sample. In addition, the AS Physical and Psychological Concerns subscales, but not the Social Concerns subscale, most strongly discriminated between the two latent classes. Finally, comparison of continuous levels of AS Physical and Psychological Concerns between FMM-derived AS latent classes and independent clinical samples of patients with anxiety disorders provided empirical support for the theorized taxonic-dimensional model of AS and anxiety psychopathology vulnerability. Findings are discussed in regard to the implications of this and related research into the nature of AS and anxiety psychopathology vulnerability.