Exposure To Allergens During Pregnancy Raises Risk For Autism, ADHD

Although there have been several attempts to determine how or why conditions like autism and other neurodevelopmental disorders, experts are still left with no clue. However, the search for any factors that may add to these psychological conditions is still ongoing. In a recent study, researchers revealed that they have their attention set on maternal allergies.

In a new study involving rats, it could begin to explain why allergies during pregnancy are identified and linked to higher risks for attention-deficit hyperactivity disorder (ADHD) and autism in children.

According to The Ohio State University, researchers at The Ohio State University found significant changes in the brain makeup of fetuses and newborn rats that were exposed to allergens during pregnancy. Animals that lived to adulthood after allergen exposure before birth showed signs of hyperactivity and antisocial behavior and decreased anxiety, as found by a research team led by Kathryn Lenz, an Ohio State assistant professor of Psychology.

"This is evidence that prenatal exposure to allergens alters brain development and function and that could be an underappreciated factor in the development of neurodevelopmental disorders," said Lenz, who presented her research on Nov. 16 in San Diego at Neuroscience 2016, the annual meeting of the Society for Neuroscience.

Even though there have already been several links associated with allergies and ADHD and autism, as well as between inflammation and risk of autism, schizophrenia and ADHD, the levels of cellular changes that could add to those connections still remain unknown.

"We're really interested in figuring out unknown factors in psychological disorders and in differences between male and female brain development as it relates to autism, ADHD, and other disorders," Lenz said.

For the study, the team sensitized female rats to an egg white protein, ovalbumin, before becoming pregnant. Then the rats were presented with the allergen, 15 days into the pregnancy, which triggered an immune response by the animal.

After that, they examined whether being exposed to the allergen before pregnancy changed the number and behavior of immune cells in the developing brain of offspring. They considered several factors in the young rats' physical activity, anxiety-like behavior, ability to learn and sociability. They also examined the density of dendritic spines in the young animals' brains. The spines protrude from neurons and are considered important to cellular-level communication in the brain.

The team found that the rats whose mothers had been exposed to an allergen had an increase in certain immune cells in the brain -- called mast cells. They also showed a reduction in another type of immune cell, microglia. These differences were seen in both sexes, reported Medical News Today.

Another prominent change was observed in their behavior. Allergic mothers' offspring were hyperactive and demonstrated the less anxiety-like behavior. According to Lenz, "Young rats engage in social play and males are rougher and tumble and usually play much more than females." However, the males in the allergy group were found to roughhouse with their peers significantly less.

"The males born to the allergen-exposed mothers looked more like females. They were more socially reserved. They were really hyperactive but socially disengaged. That looks a bit like ADHD," Lenz explained.