The researchers also have identified the vagus nerve as one of the neural pathways that carry the chemical stimuli, a finding that suggests new avenues for treating asthma and for preventing life-threatening asthmatic episodes.
The study is the first conducted in a controlled setting to link emotional states directly to physiological changes that affect asthma.
Results of the study, published by Bruce Miller, M.D., UB associate professor of pediatric psychiatry, and Beatrice Wood, Ph.D., UB assistant professor of pediatric psychiatry, appear in the May issue of the Journal of the American Academy of Child & Adolescent Psychiatry.
"These findings are clinically important because they suggest that emotional conditions, such as depression and hopelessness, may predispose asthmatic patients to airway constriction," Miller said.
"Knowing that the vagus nerve is a specific pathway for inducing these psychophysiologic responses, we can now suggest this pathway for treatment intervention." The vagus nerve is part of the autonomic, or involuntary, nervous system and is known to influence both heart rate and airway constriction.
Miller's earlier research had shown a potentially lethal association between depression and asthma. In 1989, Miller and a colleague conducted a study of circumstances surrounding the deaths of children due to asthma. They reported that "The asthmatic patients who died...constituted a group of sad and hopeless patients who were rendered psychologically and physically vulnerable [because of their emotional states] and may have suffered their fatal attacks in the face of their usual asthma triggers."
They noted further that one of the variables distinguishing the children who died from those who survived was the occurrence or anticipation, at the time of their death, of a significant separation or loss. Children with asthma who become depressed, hopeless or despairing not only leave themselves vulnerable to exacerbation of their asthma, Miller said, but the exacerbation may increase their depression, creating a destructive downward spiral.
To determine if the effects of strong emotions can be induced, quantified and correlated with a response relevant to asthma, Miller and Wood had 24 children with moderate to severe asthma watch the movie "E.T. -- The Extraterrestrial" while researchers monitored their heart rate, respiration and the oxygen saturation of the blood. The children were between the ages of 8 and 18.
"E.T." was selected because certain scenes within the movie depict situations children can identify with, such as family stress, separation, loss, sickness and fear of death," said Wood. The researchers took measurements during three scenes chosen for their ability to elicit specific emotions: sadness/hopeless/despair; happiness, and a mixture of happiness and sadness.
Results showed that heart rate and oxygen saturation became unstable during the sad scene, reflecting airway constriction. Heart rate and blood oxygen stabilized during the happy scene, indicating open airways. Results were mixed during the scene depicting both happiness and sadness. In addition, changes in activity of the vagus nerve correlated closely with changes in the children's emotional responses.
Miller said the findings suggest that antidepressants that lessen the response of the vagus nerve to emotions could be effective in treating asthma, as well as depression, in these children.
"We suspect that when a patient suffers from both asthma and depression, there may be undertreatment for the depression," Miller noted. "We need to point out to physicians that treating the depression can improve asthma symptoms, as well as mood."
The research was supported by grants from the National Jewish Center for Immunology and Respiratory Medicine and the National Institute of Mental Health.