Women with ancestral exposure to toxins may be more susceptible to stress, according to a recent study.

Researchers from the University of Texas at Austin and Washington State University found that female rats whose great grandparents were exposed to vinclozolin become much more vulnerable to stress, becoming more anxious and preferring the company of novel females to familiar females. Males who have the same combination of ancestral exposure and stress do not have the same adverse effects.

"These results should concern us all because we have been exposed to endocrine disrupting chemicals for decades and we all go through natural challenges in life," David Crews, lead author of the study and the Ashbel Smith Professor of Zoology and Psychology at The University of Texas at Austin, said in a statement. "Those challenges are now being perceived differently because of this ancestral exposure to environmental contamination."

For the study, researchers ancestrally exposed rats to a common fungicide, vinclozolin. To test the effects of stress on rats, the researchers confined some of them to soft, warm cylinders for six hours a day for three weeks. This was done during adolescence, a developmentally sensitive time of life for rats, just as for humans. Months later, the researchers tested the brain chemistry, brain function, gene expression and behavior of the rats as adults.

They found that for female rats, ancestral exposure to vinclozolin alone or stress during the animal's adolescence alone had negligible effects on the rats' hormonal balance and behavior. However, the combination of ancestral exposure and stress caused the female rats to have dramatically higher levels of corticosterone (a stress hormone similar to cortisol in humans), higher expression of genes associated with anxiety and more anxious behaviors.

Crews said that following the exposure to endocrine disrupting chemicals (EDCs), what is being passed down from generation to generation is not a change in the genetic code of the animals, but rather a change in the way specific genes are expressed. 

The findings were recently published in the journal Endocrinology.