Perna G, Brambilla F, Arancio C, Bellodi L
Department of Neuropsychiatric Sciences, University of Milan San Raffaele Hospital, Italy.
Biol Psychiatry. 1995 Apr 15;37(8):528-32. doi: 10.1016/0006-3223(94)00154-U.
In a double blind, random, cross-over design, 10 patients and seven controls inhaled one vital capacity of 35% CO2-65% O2 during their early-follicular and midluteal phases. Anxiety after CO2 intake was significantly stronger in the early-follicular phase than in the midluteal phase for patients. Controls had no anxiety reactions.