Check Up: Stress may have genesis in womb

Researchers have shown previously that maternal stress during pregnancy may have negative consequences for the fetus, both in humans and laboratory animals.

A new study from the University of Pennsylvania suggests that in mice, such impacts - namely, an increased sensitivity to stress - are passed along even to the fetus' children.

The finding, published in the Journal of Neuroscience, is an example of epigenetics: the study of how genes can be switched on or off in ways that may be inherited by future generations.

This type of phenomenon is thought to play a role in some cases of autism and schizophrenia. In a well-known Danish study, for example, the risk that a child would grow up to develop schizophrenia was higher when the mother had experienced the death of a close relative during the first trimester of pregnancy.

But it is hard to get at the mechanisms for that in people - hence the new mouse study by Tracy L. Bale, an associate professor of neuroscience at Penn's School of Veterinary Medicine.

Bale and graduate student Christopher P. Morgan subjected pregnant mice to a variety of stressful (yet painless) situations: wet bedding, exposure to fox odor, and multiple cage changes, to name a few.

Months later, they studied the grandchildren of these mice, but only those grandchildren that had been born to male offspring of the original stressed-out moms.

They did that to eliminate any chance that the impact of maternal stress was being passed along through some deficiency in child-rearing. Male mice were not involved in taking care of the young.

"If fathers can pass it to sons, then we know some mark has to be found in the sperm," said Bale, who also is affiliated with the psychiatry department at Penn's Perelman School of Medicine.

Indeed, the grandsons were more sensitive to stress, as measured by their reaction to being hung by the tail for a few minutes. Animals that didn't try to resist, remaining immobile for much of the time, were deemed to be more sensitive to stress. Moreover, genes involved in the grandsons' brain development were turned on or off in a pattern akin to that in the female mouse brain.

Bale hopes the research could lead to earlier diagnosis of various mental illnesses, and earlier intervention.

- Tom Avril