CO2-induced panic attacks: a twin study.
OBJECTIVE: The authors investigated the role of genetic factors in 35% CO2-induced panic attacks. METHOD: Ninety twins recruited from the general population were challenged with one-vital-capacity inhalations of 35% CO2-65% O2. Probandwise concordance rates were calculated and rates compared for monozygotic and for dizygotic twins. RESULTS: A significantly higher concordance was found for 35% CO2-induced panic attacks among monozygotic than dizygotic twins (55.6% versus 12.5%). CONCLUSIONS: These results suggest a relevant role of genetic factors in 35% CO2-induced panic attacks.