296 TREATMENT OF SPECIFIC ANXIETY DISORDERS
Hypothesis 1. Interoceptive Hypersensitity
Individuals with panic disorder will exhibit selective attention to and greater vigilance for
internal somatic and mental sensations than individuals without panic disorder.
If panic disorder is characterized by heightened vigilance and response to bodily
sensations, at the very least one would expect individuals with panic disorder to report
greater response to physical sensations on questionnaire and interview measures. In
several studies individuals with panic disorder and agoraphobia scored significantly
higher on the Body Sensations Questionnaire (BSQ), which assesses fear of 17 physi-
cal and mental sensations common in anxiety and panic, compared to individuals
with other anxiety disorders or nonclinical control groups (e.g., Chambless & Gracely,
1989; Kroeze & van den Hout, 2000a; Schmidt et al., 1997). Similarly McNally et al.
(1995) found that individuals with panic reported more severe physical sensations than
nonclinical controls, with fear of dying, fear of heart attack, fear of losing control,
and tingling being the best discriminators. However, individuals with panic disorder
may have heightened discomfort intolerance, as indicated by a reduced ability to with-
stand unpleasant physical sensations and pain more generally (Schmidt & Cook, 1999;
Schmidt, Richey, & Fitzpatrick, 2006). Overall there is fairly consistent evidence that
individuals who experience recurrent panic attacks report greater sensitivity to physical
sensations and are more likely to interpret these symptoms negatively (see also Taylor,
Koch, & McNally, 1992).
Stronger support for the interoceptive hypersensitivity hypothesis comes from
experimental studies that induce physical sensations through various biological chal-
lenges such as hyperventilation, inhalation of CO 2 -enriched or O 2 -enriched air, lactate
infusion, and the like. A consistent finding across these experimental studies is that
panic disorder patients evidence a significantly greater subjective response to the sensa-
tions produced by the inductions as indicated by higher ratings on the intensity, sever-
ity, and anxiousness associated with the bodily sensations produced by the induction
manipulations (e.g., Antony, Coons, McCabe, Ashbaugh, & Swinson, 2006; J. G. Beck,
Ohtake, & Shipherd, 1999; Holt & Andrews, 1989; Rapee, 1986; Schmidt, Forsyth,
Santiago, & Trakowski, 2002; Zvolensky et al., 2004).
If panic disorder is characterized by increased vigilance for physical sensations, we
might expect panic disorder patients to demonstrate greater acuity or perception of their
physiological responding. A number of studies have investigated heart rate perception
in panic disorder. In an early study by Pauli et al. (1991) panic disorder individuals who
wore an ECG recorder over 24 hours did not report significantly more cardiac percep-
tions than healthy controls but significantly more self- reported anxiety was associated
with the perceptions. Moreover, heart rate acceleration occurred after cardiac percep-
tions that were associated with intense anxiety whereas cardiac perceptions associated
with no anxiety led to heart rate deceleration.
Some studies have used a “mental tracking” procedure in which individuals silently
count felt heartbeats without taking their pulse. Early findings suggested that individu-
als with panic disorder had better heartbeat perception than other patient groups or
nonclinical controls (e.g., Ehlers & Breuer, 1992; Ehlers, Breuer, Dohn, & Fiegenbaum,
1995), but a later reanalysis of pooled data across different studies found that accurate
heartbeat perception was more often evident in panic disorder compared to depressed