Effects of 7.5% CO2 challenge in generalized anxiety disorder.
We have previously developed a putative model of generalized anxiety disorder in healthy volunteers using a 20-minute 7.5% carbon dioxide (CO(2)) inhalation challenge. The aim of this study was to validate the 7.5% CO(2) paradigm by assessing its effects in patients with generalized anxiety disorder in a test-retest design. Twelve medication-free generalized anxiety disorder patients attended our lab for two study days. On each study day placebo (compressed air) and 7.5% CO(2) mixture were randomly administered over 20 min, at least 30 min apart, in a single blind, randomized, placebo-controlled cross-over design. Subjective ratings, cardiovascular measures and cortisol levels were collected throughout. CO(2) challenge significantly increased ratings for anxiety and other subjective symptoms associated with generalized anxiety disorder, compared with air. It also significantly increased systolic blood pressure on day 2, indicating increased autonomic arousal. There was no change between the two test days in mean anxiety rating scores, and there also appeared to be a correlation for individual scores on a number of the subjective measures. In conclusion, 20 min of 7.5% CO(2) gas inhalation increases anxiety responses in patients with generalized anxiety disorder, and this is reliable over time.
Seddon
Kate
K
University of Bristol, Psychopharmacology Unit, Bristol, UK. kate.seddon@nhs.net
Morris
Kelly
K
Bailey
Jayne
J
Potokar
John
J
Rich
Ann
A
Wilson
Sue
S
Bettica
Paolo
P
Nutt
David J
DJ
D000328:Adult; D001007:Anxiety / Q000503:physiopathology*; D001008:Anxiety Disorders / Q000139:chemically induced* / Q000503:physiopathology; D001794:Blood Pressure / Q000187:drug effects; D002245:Carbon Dioxide / Q000008:administration & dosage / Q000009:adverse effects* / Q000494:pharmacology; D018592:Cross-Over Studies; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D016584:Panic Disorder / Q000139:chemically induced* / Q000378:metabolism / Q000503:physiopathology; D011569:Psychiatric Status Rating Scales; D016037:Single-Blind Method; D055815:Young Adult
D002245:Carbon Dioxide