Children who are abused can be left with physical, "molecular scars" on their DNA that last well into adulthood, according to a new study from Harvard University and the University of British Columbia.

The findings could one day impact disease research as well as criminal investigations, though more work needs to be done before experts know how the "tagging" — known as DNA methylation — affects a victim's long-term mental and physical health.

But Nicole Gladish, a PhD candidate at UBC and co-author of the study, said the research is a promising development for researchers looking to better understand the link.

"It's a really good first step," she said.

Pilot study

A team of UBC researchers looked at chemical tags on the DNA of 34 adult men for the study, published in Translational Psychiatry on Tuesday.

Gladish researchers were looking for methylation in the mens' sperm.

If genes are lightbulbs, Gladish explained,methylation is a "dimmer switch" that affects how cells are turned on or off.

Seventeen of the participants had reported being physically attacked as children, with two saying they'd been sexually abused.

Gladish said there was a "striking" difference in tagging between those who'd been abused and those who had not.

"Typically, most studies see [percentage] differences about five per cent to 10 per cent ... some of these differences were very large in the 20 per cent range up to 29 per cent," said Gladish, who analyzed much of the data for the study.

"Essentially, [it means] these little tiny tags on the DNA are kind of put into place at the time of abuse and are just present and persist throughout the life's course."

Nicole Gladish is a PhD candidate at UBC’s Department of Medical Genetics and co-author of the study. (Nicole Gladish)

Gladish said researchers circled back to check if there could be other external factors causing the tagging — smoking, PTSD, more recent trauma — but the differences weren't there, leading researchers to believe the tags were from childhood trauma.

As for how methylation impact a person's day-to-day health, Gladish said that's not clear yet — but the fact that researchers have linked child abuse and tagging is a good move forward.

"I wasn't anticipating getting anything because the sample size was so small …To get the type of signal that we got, it was really exciting."

Gladish also said the study could pave the way for genetic tests that would indicate whether someone had been abused as a child — a tool that could be used to weigh allegations of abuse.

It could also be used to determine how childhood stress can lead to diseases in adults — something long hypothesized in science.

"We don't know what goes on in the body between the abuse and diseases that happen later in life," Gladish said.

Gladish said it's not yet clear if "tags" on a victim's DNA can be passed along to their children. She also said the study was restricted to men due to the difficulty in extracting egg cells from women — who, statistically, are more likely to be abused as children.

Scientists are increasingly looking into what turns genes "on and off" over the course of a lifetime, known as the study of epigenetics, because the ons and offs are believed to be influenced by external forces: like natural environment or abuse.

The men who donated their sperm for the study were already part of a larger, separate study being conducted at Harvard. The data was gathered at the Ivy League University and analyzed at UBC.

Read more from CBC British Columbia