You are here:
A systematic review and meta-analysis investigating the relationship between exposures to chemical and non-chemical stressors during prenatal development and childhood externalizing behaviors
Citation:
Nilsen, F., J. Frank, AND N. Tulve. A systematic review and meta-analysis investigating the relationship between exposures to chemical and non-chemical stressors during prenatal development and childhood externalizing behaviors. International Journal of Environmental Research and Public Health. Molecular Diversity Preservation International, Basel, Switzerland, 17(7):2361, (2020). https://doi.org/10.3390/ijerph17072361
Impact/Purpose:
This work investigated the relationship between prenatal exposure to chemical and non-chemical stressors, as well as genetic predisposition to childhood externalizing behavior disorders through systematic review and meta-analysis. We observe that chemical exposures, non-chemical stressors, and inherent characteristics influence behavior individually, and synergistically. The existing data highlights the need for interdisciplinary studies examining more than one type of stressor, as well as in depth analysis of individual stressors to better understand the complex interactions described in the literature. This work will aid future studies related to children's mental health through the research gaps identified and the recommendations made to further examine this complex issue.
Description:
Adverse childhood behavioral outcomes have been linked to low quality intrauterine environments caused by prenatal exposures to both chemical and non-chemical stressors. The effect of the many stressors a child can be prenatally exposed to may be influenced by complex interactive relationships that are only beginning to be understood. Chemical stressors can influence behavioral outcomes through competitive inhibition of the monoamine oxidase A (MAOA) enzyme, which is involved in serotonin metabolism and the neuroendocrine response to stress. The MAOA gene has two genotypes (low activity [L]; high activity [H]) that influence MAOA enzyme production and serotonin metabolism. The MAOA-L variant is often associated with externalizing behaviors in children and adults, as less serotonin is metabolized by individuals with this genotype, resulting in altered moods. The combination of chemical MAOA inhibition with the MAOA-L genotype may lead to drastic adverse behavioral changes. Non-chemical stressors, particularly those associated with violence, have been shown to influence and exacerbate the externalizing behavioral outcomes associated with MAOA-L. Many researchers have highlighted the importance of good maternal health during pregnancy and have noted the adverse developmental effects of high stress during pregnancy. However, the body of research examining the effects of other non-chemical stressors on development and childhood outcomes as a result of gestational exposures is scarce but expanding. In this systematic review, we examine the extant literature to explore the interrelationships between exposures to chemical and non-chemical stressors (specifically traumatic experiences), MAOA characteristics, and childhood externalizing behaviors. We observed that exposures to chemical stressors (recreational drugs and environmental chemicals) are significantly related to adverse externalizing behaviors in children. We also observed that existing literature examining the interactions between MAOA characteristics, exposures to chemical stressors, and traumatic experiences and their effects on behavioral outcomes is sparse, and that maternal stress may be an avenue to link these concepts. We recommend that future studies investigating childhood behaviors include chemical and non-chemical stressors and children's inherent genetic characteristics to gain a holistic understanding of the relationship between prenatal exposures and childhood behavioral outcomes.
