Dad's chronic stress could take a toll on his children's stress response because of the effects on his sperm, an animal study suggests.
Scientists at the University of Pennsylvania found that male mice exposed to chronic stress also experienced epigenetic effects (where expression of genes is altered by outside factors) on their sperm. As a result, the mice's offspring had blunted stress responses. The researchers said this is because of the reprogramming of a brain region known to play a role in stress, called the hypothalamic-pituitary-adrenal, or HPA, axis.
"It didn't matter if dads were going through puberty or in adulthood when stressed before they mated. We've shown here for the first time that stress can produce long-term changes to sperm that reprogram the offspring HPA stress axis regulation," study researcher Tracy L. Bale, Ph.D., who is an associate professor of neuroscience at the university, said in a statement. "These findings suggest one way in which paternal-stress exposure may be linked to such neuropsychiatric diseases."
The study, published in the Journal of Neuroscience, involved subjecting male mice to chronic stress for six weeks. They were put through stress -- which included exposing them to predator smells, noise, foreign objects or new environments -- during their puberty stage or when they were adult mice. Then, the mice were bred with other mice to produce offspring.
Compared to offspring bred from not-stressed-out mice, researchers found that the offspring from the stressed mice produced blunted levels of corticosterone, the mouse version of the human stress hormone cortisol. Researchers noted that any upheavals in the way the stress pathway is normally supposed to work -- whether it involves a heightened response or a blunted response -- may not be good because it means the mouse isn't responding to stress appropriately, and could lead to potential psychiatric disorders. However, they also noted that this effect on the offspring could potentially serve as an evolutionary benefit, preparing them for a supposedly more-stressful environment.
The offspring of the stressed mice also experienced gene expression changes in stress-related brain regions. The researchers noted gene expression changes on the stressed father mice's sperm.
The field of epigenetics is still relatively new, but other research has also suggested parents can pass on epigenetic traits to their offspring. LiveScience reported on a 2005 study that the babies of pregnant women who experienced stress from witnessing the 9/11 attacks were "passed on" higher cortisol levels by their mothers.
And a 2011 study in the journal Cell in flies showed that stress effects can be "inherited" because of changes to the cell nucleus material chromatin.