Repeated exposure to interoceptive cues: does habituation of fear occur in panic disorder patients? A preliminary report.

In order to explore the mechanism of action of interoceptive exposure, 12 Panic Disorder (PD) patients were presented with two sessions of repeated CO2 inhalation. Two distinct patterns of responding were noted. The first pattern was described as habituation of fear (n = 6). These patients showed decrements in pre- and post-inhalation anxiety during both sessions (with more rapid decline during session 2), as well as spontaneous recovery of fear at the onset of session 2. The second pattern indicated fear sensitization. These patients showed relatively low levels of anticipatory anxiety preceding CO2 inhalation during both sessions but reported robust increases in fear following gas inhalation. The extent of this increase was slightly less during session 2 relative to session I and did not appear to be mediated by cardiovascular arousal, as both groups showed rapid HR habituation during both sessions. Results are discussed in light of current theories of PD and its treatment.