A segregation study of panic disorder in families of panic patients responsive to the 35% CO2 challenge

Background: A genetic component has a role in the etiology of Panic Disorde r (PD) and a familial association between PD and CO2 hypersensitivity have been repeatedly described. Methods: Complex segregation analysis was performed on a sample of 165 fami lies of PD probands and on the subgroup homogeneous for CO2 hypersensitivit y, using Regressive Logistic Models. The only relatives considered to be af fected were those with PD. Relatives have been diagnosed according to Famil y History Method. Results: A Mendelian hypothesis was compatible with our data, without disti nction between different models of transmission. The Akaike's Information C riterion values indicated that the Additive model was the most parsimonious , with a gene frequency of .0005, incomplete penetrance and a phenocopy rat e of .00029. By subdividing the families according to the probands' respons es to CO2 inhalations, probands of 134 families were hypersensitive to CO2. The analysis performed on this subgroup supported the existence of a SML w ith a best fit for a Dominant model. Conclusions: A SML account for genetic transmission in PD families and 35% CO2 challenge test may individuate a genetically homogeneous subgroup of pa tients with PD. (C) 1999 Society of Biological Psychiatry.