Previous studies have found a relationship between asthma and other anxiety disorders and a higher risk of depression. The reason(s) for the association between asthma and mental disorders is unknown. Researchers theorize asthma could increase the risk of anxiety disorders, or anxiety disorders might cause asthma, or there could be a common risk factors for both asthma and anxiety disorders.
Researcher Renee D. Goodwin, Ph.D., assistant professor of Epidemiology at the Mailman School of Public Health, did a study of 3,065 male twin pairs, who had lived together in childhood, and who had both served on active military duty during the Vietnam War. The group included both identical twins, who share all the same genetic material, and fraternal twins, who share only half of the same genetic material.
Goodwin found that those who suffered from asthma were 2.3 times more likely to suffer from post-traumatic stress disorder (PTSD) symptoms than those did not have asthma. She did not find that there was a genetic link between asthma and PTSD because otherwise there would not have been a 2.3 times differential between the twin with asthma and the one free of it.
The reason for the difference may be that having asthma places adults at increased risk for PTSD because they feel they are likely to be exposed to a traumatic situation because of the life-threatening chronic medical condition. It is also possible the traumatic stress compromised the individuals immune functions, which led to an increased vulnerability to immune-system-related diseases–including asthma.