Maternal exposure to insecticides potential cause of autism in children

Issue: September 2018

Study findings published in the American Journal of Psychiatry revealed that maternal exposure to insecticides during pregnancy was linked to autism in offspring.

Perspective from R Scott Benson, MD

“Autism is a neurodevelopmental disorder that causes substantial distress and impairments in psychological and social functioning, and its causes remain largely unknown,” Alan S. Brown, MD, MPH, professor of psychiatry and epidemiology at Columbia University Medical Center and director of the unit in birth cohort studies at New York State Psychiatric Institute, told Infectious Diseases in Children. “Organic pollutants such as pesticides are widespread in the population. Research on this topic offers potential for prevention and a better understanding of the developmental mechanisms that influence brain development and risk for autism.”

Using maternal biomarkers of exposure, researchers examined the relationship between elevated maternal levels of persistent organic pollutants and autism in offspring using data derived from a Finnish national birth cohort study.

In the study, persistent organic pollutants included the insecticide dichlorodiphenyltrichloroethane (DDT), its metabolite p,p:-dichlorodiphenyl dichloroethylene (p,p:-DDE) and polychlorinated biphenyls (PCBs). The investigators examined cases of autism in children born between 1987 and 2005. To determine levels of p,p:-DDE and total levels of PCBs, they assessed maternal serum specimens from early pregnancy in cases of childhood autism and matched control participants (n = 778 pairs).

When maternal p,p:-DDE levels were in the top 75th percentile of the control distribution, the odds of autism in offspring were increased by 32%, adjusting for maternal age, parity and history of psychiatric disorders (OR = 1.32; 95% CI, 1.02-1.71). However, there was no increase in the odds of autism for maternal PCBs exposure above the 75th percentile. Furthermore, the link between high maternal p,p:-DDE levels and the odds of autism was significant among boys (OR = 1.35; 95% CI, 1.02-1.8) but not girls.

The results also showed that the odds of autism with intellectual disability were higher when mothers had p,p:-DDE levels above the 75th percentile threshold (OR = 2.21; 95% CI, 1.32-3.69) compared with case participants without intellectual disability.

“Clinicians will be more aware that there may be important environmental contributors to autism, particularly in pregnant patients, and consider recommending measures aimed at reducing exposure to organic pollutants, including pesticides,” Brown said.

The researchers emphasized that these results need to be replicated in future studies – by Savannah Demko

Reference:
Brown AS, et al. Am J Psychiatr. 2018;doi:10.1176/appi.ajp.2018.17101129.

Disclosures: The authors report no relevant financial disclosures.

Perspective

R Scott Benson, MD

This study presents an exciting advance in the sense that we have the technology to measure these chemicals, and we can apply this technology to a large dataset in our search for possible causes of the symptoms of autism. We already knew that DDT could cause fairly severe damage, and it has been previously associated with intellectual disability, but the article suggests the chemical might be responsible for other subtle changes in brain function.

I am excited that we are looking to find the possible causes of disability in children who have autism spectrum disorder. Our treatments are only partially effective; the best approach is going to be prevention.

We have other examples of having to wait for a science breakthrough to make sense of disease states. Think about the technology to define the aminoacidurias, or the relationship between rubella virus and birth defects. Children would take the virus to school and infect their teachers, many of whom were young pregnant women. In many cases the fetus died, and in other cases the baby was born with significant birth defects. It took a long time to understand the association. We forget that the germ theory of disease is from the 1880s, so the idea of germs and viruses causing disease and disabilities is not that old. Our ability from a technology point of view to measure these chemicals is fairly new, as is having the big datasets that can collect that information and maintain it over time.

R Scott Benson, MD

Child and adolescent psychiatrist

Disclosures: Disclosure: Benson reports no relevant financial disclosures.