Clinical features of respiratory and nocturnal panic disorder subtypes.

Our aim is to compare the panic disorder (PD) respiratory subtype and the nocturnal panic subtype. A group of 193 PD patients (DSM-IV) was examined in the Laboratory of Panic and Respiration in the Institute of Psychiatry of the Federal University of Rio de Janeiro. The diagnoses were made using the SCID-I for DSM-IV. The subtypes were the respiratory (with 4 out of 5 prominent respiratory symptoms during the panic attacks [PA]) vs. non-respiratory, likewise PD with nocturnal (during sleep) PAs vs. PD with only diurnal PAs. The respiratory subtype accounted for 56.5% (n=109) of our sample; the non-respiratory subtype, 43.5% (n=84); the nocturnal subtype, 49.2% (n=95); and the non-nocturnal subtype, 50.8% (n=98). Despite a rich literature concerning correlations between the respiratory system and nocturnal panic attacks, our data do not support these findings, as the comparison of proportions in the respiratory and nocturnal groups did not differ. The non-nocturnal subtype was significantly associated with agoraphobia, and the respiratory subtype was not associated with these variables.