Panic Disorder 297
and normal controls but not when compared to patients with other anxiety disorders
(van der Does, Antony, Ehlers, & Barsky, 2000). Moreover, only a minority of the panic
disorder patients was classified as accurate perceivers (17%). Thus accurate heartbeat
perception appears to be a characteristic of having frequent episodes of clinical anxiety
as opposed to panic attacks per se.
An automatic, preconscious attentional processing bias for physical cue words
should be apparent if panic is characterized by hypervigilance for bodily sensations.
Lundh and colleagues (1999) found that panic disorder patients had significantly higher
Stroop interference effects to panic- related words than nonclinical controls at both a
subliminal and a supraliminal level but this biasing effect was also evident for interper-
sonal threat words. In addition the panic disorder group identified more panic- related
words presented at perceptual threshold (see also Pauli et al., 1997). Using a novel vari-
ant of the dot probe detection task in which response latency was assessed to a letter
preceded by a snapshot sample of ECG heart rate data or a moving line, Kroeze and van
den Hout (2000a) found evidence that the panic group was more fully attentive to the
ECG trials than the control group (see Kroeze & van den Hout, 2000b, for contrary
finding).
In a study involving 20 individuals with claustrophobia, those told to concentrate
on their bodily sensations while in an enclosed chamber reported significantly higher
fear and panic scores, and experienced a higher rate of panic attacks than individuals in
the control (distraction) group (Rachman, Levitt, & Lopatke, 1988). Strenuous physi-
cal exercise is a naturalistic situation that normally increases attention to physical state.
Furthermore, vigorous exercise increases blood lactate levels, which individuals with
panic might find less tolerable given their heightened reactivity to sodium lactate infu-
sion (Liebowitz et al., 1985). So, one might expect panic patients to be less tolerant of
strenuous physical exercise. Interestingly, it appears that individuals with panic disorder
are able to engage in vigorous physical exercise without experiencing thoughts or feel-
ings indicative of panic even though the exercise produces blood lactate levels that are
equal to or greater than those attained in lactate infusion studies (Martinsen, Raglin,
Hoffart, & Friis, 1998).
Although individuals with panic disorder may have greater physiological reactiv-
ity such as a elevated respiratory rate, heart rate, and blood pressure, and lower skin
temperature during biological provocations that induce bodily sensations (J. G. Beck et
al., 1999; Craske, Lang, Tsao, Mystkowski, & Rowe, 2001; Holt & Andrews, 1989;
Rapee, 1986; Schmidt et al., 2002), the physiological differences are relatively modest
and inconsistent across studies, with some even reporting negative results (Zvolensky
et al., 2004). On the other hand, differences in perceived intensity and distress of the
physical sensations produced by these biological challenges have been robust and quite
consistent across studies (e.g., J. G. Beck et al., 1999; Holt & Andrews, 1989; Rapee,
1986). In a recent study Story and Craske (2008) found that individuals at risk for panic
(high anxiety sensitivity and a history of panic attacks) reported significantly more
panic symptoms following false elevated heart-rate feedback than low-risk individuals,
even though there were no group differences in actual heart rate. Together these findings
provide strong evidence for the cognitive perspective on panic disorder, suggesting that
the main difference is in the perception and interpretation of physical changes rather
than in actual physiological responses.