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. https://ajp.psychiatryonline.org/doi/10.1176/appi.ajp.2018.17101129
Abstract
Objective:
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.
Method:
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.
Results:
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.
Conclusions:
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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