Toxic stress in pregnancy and infancy causes asthma: Dose matters

Published Online: March 4, 2016

Exposure to environmental toxins during pregnancy and/or early childhood can alter the normal course of lung development, resulting in changes that affect a child’s risk of developing asthma.  Lung growth progresses sequentially with specific functions and processes developing in a particular order, thus the effects of toxins on asthma risk depend on both timing and dose of exposure.  Identifying important risk factors as early as possible in development that contribute to heightened asthma risk is critical so that interventions can be applied early to promote optimal lung development.  

In The Journal of Allergy and Clinical Immunology (JACI), Lee and colleagues present the first prospective analyses considering the effects of both dose and timing of exposure to toxic stress in early life on asthma onset in children.   These investigators followed 765 mother-infant pairs enrolled during pregnancy in the Asthma Coalition on Community, Environment, and Social Stress (ACCESS) project in urban Boston, MA to examine whether children born to mothers’ experiencing a greater number of adverse life events during pregnancy as well as the child’s first two years of life were more likely to develop asthma by age 6 years.    

Pre- and postnatal maternal stress was measured using the Crisis in Family Systems-Revised (CRISYS-R) survey, which measures negative life events (NLEs) across a number of life domains including financial difficulties, relationship problems, safety in their homes and communities, and experiences of racism or discrimination.  While we all experience day to day difficulties, stress becomes toxic when we experience environmental demands that pile up and overwhelm our ability to cope and manage these challenges.  A dose effect can therefore be seen when women experience difficulties across an increasing number of life domains.  Mothers also reported whether a healthcare provider had diagnosed their children with asthma during follow up.  Importantly, this study controlled for other factors that could be correlated with increased stress as well as asthma risk in children such as socioeconomic status, whether mothers smoked, and exposure to other environmental toxins such as household allergens or air pollutants.  

The authors found that toxic stress occurring in both pregnancy and early infancy was associated with increased risk for asthma development in these children.  Moreover, dose mattered.  Children born to mothers experiencing difficulties over 5 or more life domains were two to three times more likely to develop asthma by the time they started school compared to children of women reporting the lowest levels of stress. Also, children born to women experiencing the greatest number of adverse events in both pregnancy and early infancy were at heightened risk for asthma – an association that particularly impacted girls.  

These findings show that children are at increased risk of developing asthma when their mothers experience toxic levels of stress in the perinatal period.  Clinicians should counsel pregnant women and young mothers on the role of psychological stress in this context, to raise awareness of the links between mothers’ stress and health of the next generation.  The demonstration that dose matters is critical here. While it is not necessary to eliminate stress altogether, interventions focused on reducing stress levels in the prenatal and early postnatal periods may reduce asthma risk in children.  Clinical trials examining stress reduction modalities are needed to see if we can indeed prevent asthma onset.  

The Journal of Allergy and Clinical Immunology (JACI) is an official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.

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