Twenty-four panic disorder patients and 25 nonclinical subjects underw
ent double-breath inhalations of 5, 10, and 20% carbon dioxide (CO2) o
r room air. All subjects were blind to inhalation content and were req
uired to guess if the inhalation contained CO2. There was no significa
nt difference between groups in the accuracy with which they were able
to detect CO2 at any concentration. Similarly, the number of somatic
symptoms reported to each inhalation did not differ between groups. Th
e findings question suggestions that individuals with panic disorder a
re more accurate at detecting changes in physiology than other individ
uals.