The brain and asthma: what are the linkages?.

Stress has been associated as an important contributor to asthma in some patients. The mechanisms, however, which underlie this relationship remain unclear. In this review, the role of stress will be examined in relationship to the development of airway inflammation. As will be discussed, stress may not cause inflammation but enhances its expression when it develops to a second signal. In addition, recent studies using function magnetic resonance imaging (fMRI) have shown that specific circuits in the brain, i.e., anterior cingulate cortex and insula, are activated in relationship and intensity to the development of a late-phase response (LPR) to inhaled antigen, and that these brain signals are predictive and associated with the development of airway inflammation as measured by sputum eosinophils. Finally, in studies with mice, chronic stress enhances airway inflammation to an inhaled antigen, and these effects are associated with the development of corticosteroid unresponsiveness. Collectively, these data suggest that chronic stress enhances asthma severity through a number of novel mechanisms and the resulting increase in severity of asthma may not be responsiveness to standardly used treatments.