Multiple chemical sensitivity, a condition that can be debilitating for those who have it and frustrating for doctors trying to treat it, may be genetically linked to panic disorder. Now called idiopathic environmental intolerance, or IEI, the illness produces a variety of symptoms in people when they are exposed to common chemicals and pollutants. Some of these symptoms – such as chest tightness, breathlessness and palpitations – also characterize panic disorder, and researchers have questioned the relationship between the two conditions. Building on the 1999 discovery of an association between a variation of a gene called CCK-BR and panic disorder, Karen Binkley, assistant professor in the department of medicine, examined this gene in people with and without IEI. Forty per cent of IEI sufferers had the genetic variation, compared with only nine per cent of those in the control group. “These results suggest that panic disorder and IEI may share an underlying neurogenetic basis, which could account for the similarity in symptoms and provide a basis for treatment,” says Binkley, lead author. Funding for the study came in part from the Ontario Mental Health Foundation and the Canadian Institutes of Health Research.