An expanded anxiety sensitivity index: evidence for a hierarchic structure in a clinical sample

Anxiety sensitivity (AS) is the fear of anxiety-related sensations. According to Reiss's (e.g., Reiss, 1991) expectancy theory, AS amplifies fear and anxiety reactions, and plays an important role in the etiology and maintenance of anxiety disorders, particularly panic disorder. Recent evidence suggests that AS has a hierarchical structure, consisting of multiple lower order factors, loading on a single higher order factor. If each factor corresponds to a discrete mechanism (Cattell, 1978), then the results suggest that AS arises from a hierarchic arrangement of mechanisms. A problem with previous studies is that they were based on the 16-item Anxiety Sensitivity Index, which may not contain enough items to reveal the type and number of lower order factors. Also, some of the original ASI items are too general to assess specific, lower order factors. Accordingly, we developed an expanded measure of AS--the ASI-R--which consists of 36 items with subscales assessing each of the major domains of AS suggested by previous studies. The ASI-R was completed by 155 psychiatric outpatients. Factor analyses indicated a four-factor hierarchical solution, consisting of four lower order factors, loading on a single higher factor. The lower order factors were: (1) fear of respiratory symptoms, (2) fear of publicly observable anxiety reactions, (3) fear of cardiovascular symptoms, and (4) fear of cognitive dyscontrol. Each factor was correlated with measures of anxiety and depression, and fear of cognitive dyscontrol was most highly correlated with depression, which is broadly consistent with previous research. At pretreatment, patients with panic disorder tended to scored highest on each of the factors, compared to patients with other anxiety disorders and those with nonanxiety disorders. These findings offer further evidence that Reiss's expectancy theory would benefit from revision, to incorporate the notion of a hierarchic structure of AS.