Evidence continues to correlate prenatal and early life stress with childhood asthma.1 Although the psychological connection to asthma and other atopic diseases dates to the 12th century, it has wavered between a strictly inflammatory disease and a psychiatric one.1 The latest resurgence began in earnest in the 1990s with funding by the National Institutes of Health to examine the connection between stress and asthma.2
Researchers and clinicians now have a greater appreciation for the developments that occur in utero and during the first 2 years of life.1 Prenatal insults to the immune, neuroendocrine, and antioxidant defenses, as well as maternal anxiety and depression, contribute to wheezing and asthma.1 The exact mechanisms for how all of these toxicities affect the respiratory system, however, have yet to be fully explained.1
Early Life Stress Affects Asthma Vulnerability
Some of the theories of how stress affects respiratory health include the disturbance of the hypothalamic-pituitary-adrenal axis and imbalance or dysfunction of the autonomic nervous system.1 A mother who is stressed can influence the functioning of her baby’s immune system.1 Studies have associated high levels of the stress hormone cortisol in pregnant women with poor respiratory outcomes in their infants.1 It is thought that when the mother’s cortisol circulates to the fetus, it binds to the endogenous and exogenous glucocorticoid receptors, which affects the fetal hypothalamic-pituitary-adrenal axis.3
Stress in women tends to have a cumulative effect. Women who experienced interpersonal trauma such as violence and child abuse — even long after the episodes — tended to have higher cortisol levels, greater imbalance in the autonomic nervous system, and more inflammation in pregnancy than women who had not endured such stress.1
Another theory posits that women who are stressed may be more likely to smoke, which in turn can result in preterm delivery and lower birth weight babies who then may have a greater risk for asthma development. Interestingly, there may be a sex-specific reaction to maternal stress: boys appear to be vulnerable in both prenatal and postnatal periods, whereas girls may only be affected postnatally.1
To test the theory that prenatal stress is responsible for a host of allergic diseases in childhood, Smejda and colleagues sought to determine the correlation between maternal stress and atopic dermatitis, food allergy, wheezing, and recurrent respiratory tract infections.3 The study examined 370 mother-child pairs and assessed maternal distress in women who worked at least 1 month during their pregnancy.
The study found that women who registered high stress levels as measured by the Subjective Work Characteristics Questionnaire, the Perceived Stress Scale, and the Social Readjustment Rating Scale had children who had a greater risk of wheezing during the first year of life (odds ratio [OR], 1.09; 95% CI, 1.01-1.02). Even when adjusted for the number of infections and maternal smoking, children whose mothers reported prenatal stress were still more likely to experience wheezing.3 Stress, however, did not affect the risk for atopic dermatitis or food allergies. There was an association between maternal stress and recurrent respiratory tract infections in the children, but it was not significant.3