Thursday, August 16, 2018

First biomarker evidence autism Is linked to DDT

Alan S. Brown, Keely Cheslack-Postava, Panu Rantakokko, Hannu Kiviranta, Susanna Hinkka-Yli-Salomäki, Ian W. McKeague, Heljä-Marja Surcel, Andre Sourander.  Association of Maternal Insecticide Levels With Autism in Offspring From a National Birth Cohort.  Am J Psychiatry. Published Online:16 Aug 2018.


Autism is a complex neurodevelopmental disorder with a largely unknown etiology. To date, few studies have investigated prenatal exposure to toxins and risk of autism by using maternal biomarkers of exposure. Persistent organic pollutants are lipophilic halogenated organic compounds and include the insecticide dichlorodiphenyltrichloroethane (DDT), as well as its metabolite p,p′-dichlorodiphenyl dichloroethylene (p,p′-DDE), and polychlorinated biphenyls (PCBs). The objective of this study was to test whether elevated maternal levels of persistent organic pollutants are associated with autism among offspring.

The investigation was derived from the Finnish Prenatal Study of Autism, a national birth cohort study based on a nested case-control design. Cases of autism among children born between 1987 and 2005 were ascertained by national registry linkages. In cases of childhood autism and matched control subjects (778 matched case-control pairs), maternal serum specimens from early pregnancy were assayed for levels of p,p′-DDE and total levels of PCBs.

The odds of autism among offspring were significantly increased with maternal p,p′-DDE levels that were in the highest 75th percentile, with adjustment for maternal age, parity, and history of psychiatric disorders (odds ratio=1.32, 95% CI=1.02, 1.71). The odds of autism with intellectual disability were increased by greater than twofold with maternal p,p′-DDE levels above this threshold (odds ratio=2.21, 95% CI=1.32, 3.69). There was no association between total levels of maternal PCBs and autism.

These findings provide the first biomarker-based evidence that maternal exposure to insecticides is associated with autism among offspring. Although further research is necessary to replicate this finding, this study has implications for the prevention of autism and may provide a better understanding of its pathogenesis.

Commenting on the findings for Medscape Medical News, Benjamin Yerys, PhD, of the Department of Child and Adolescent Psychiatry and Behavioral Sciences and the Center for Autism Research, Children's Hospital of Philadelphia, said this study is important because it addresses the question of whether a specific insecticide chemical increases the risk that a child will have autism.

In addition, he said the study was meticulous.

"The investigators measured the chemical directly from blood given by mothers when they were pregnant, and they controlled for other risk factors that increase risk for autism, including parents' age and their own history of having a psychiatric illness. This has never been done before at such a large scale (~1500 people)," said Yerys.

"The findings raise concern that specific chemicals that were used in insecticides over 30 years ago may still exist in our food chain today and they may add risk for a child to develop autism," said Yerys.

He noted that other studies using slightly different methods to measure the insecticide exposure in mothers and smaller samples have had different results.

"These mixed findings suggest we still have much to learn about how the insecticide exposure is adding risk, and if it adds risk for all people or only some people. We also do not have a great understanding of what mothers can do to reduce or prevent the risk that is added from insecticide exposure. Therefore, it is too early to make recommendations about how to change prenatal care or screening," said Yerys.

"We do not know if a mother must have a specific genetic or biological makeup that makes her body more susceptible or resilient to the insecticide toxin. So this insecticide toxin may add risk for a specific set of women but not others," he added.

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