PHILADELPHIA, June 14 (UPI) -- Stress as a pre-adolescent or adult leaves a lasting impression on a dad's sperm that gives his kids a blunted reaction to stress, U.S. researchers say.
Study leader Tracy L. Bale of the Perelman School of Medicine and the School of Veterinary Medicine at the University of Pennsylvania in Philadelphia said the findings point to a never-before-seen link to stress-related diseases such as anxiety and depression passed from father to child.
The study involved male mice exposed to six weeks of chronic stress, before breeding, either throughout puberty or only in adulthood. Examples of stress include sudden move to another cage, predator odor such as fox urine, noise, or a foreign object in the cage.
Male mice are ideal for such an experiment because they do not participate in offspring rearing, meaning any external factors outside of germ-cell formation are essentially eliminated, Bale said.
The study, published in the Journal of Neuroscience, found offspring from paternal stress groups displayed significantly blunted levels of the stress hormone corticosterone -- in humans, it's cortisol -- in response to stress.
This stress pathway dysregulation -- when reactivity to stress is either heightened or reduced -- is a sign an organism doesn't have the ability to respond appropriately to a changing environment and as a result, their stress response becomes irregular, which can lead to stress-related disorders, Bale said.
"It didn't matter if dads were going through puberty or in adulthood when stressed before they mated," Bale said in a statement. "We've shown here for the first time that stress can produce long-term changes to sperm that reprogram the offspring hypothalamic-pituitary-adrenal axis, a region of the brain that governs responses to stress."