New England Public Radio

Updated: 4/18/14 5 p.m.

When the Boston Marathon bombing occurred, neuroscientists at Harvard University were midway through a study on trauma and the adolescent brain. As a result, they say they were able to make some new scientific links between PTSD and media exposure.

Last April, Professor Katie McLaughlin and her colleagues at Harvard were studying the brains of young people who’d been through serious adversity. They had recruited about 150 children and teens– half had reported early trauma or stress, and half had not. From previous psychological research, they knew that people who were abused or traumatized as kids have much higher rates of depression, anxiety, and substance abuse.

“And we want to understand why that is the case,” McLaughlin says. “What is it about those experiences that leads these kids to be at such elevated risk for mental health problems?”

McLaughlin and her co-investigator, Margaret Sheridan, gave their subjects emotionally taxing activities to do while in an MRI scanner — disturbing pictures to look at, or frustrating tasks — and asked them to try to cope with negative emotions. When they measured what happened in the brain, the researchers saw that children with a history of trauma had heightened activity in the amygdala — a center of emotional processing in the brain.

“The idea we’re testing this study is that exposure to trauma can disrupt typical patterns of brain development, … either making these children have more extreme emotional reaction to changes in the environment or to stressors, or making it more difficult for them to modulate their emotional responses,” she says.

In most brain studies on stress and trauma, subjects are tested through artificial situations created in the lab. But in the middle of this study, a real-life trauma occurred: the marathon bombing.

“You know, everyone was in a bit of shock after the events happened,” McLaughlin says.  “It was probably a few days later when we thought to ourselves, we have a unique opportunity here to examine predictors of how children respond to these kinds of unpredictable widescale traumatic events.”

If — as in many studies — all you have is a picture of the brain after a traumatic event, it’s hard to know whether the brain changed as a result of the event or whether the brain was already predisposed to react badly to trauma. But McLaughlin had a group of subjects whose brains had been scanned before the bombing. So she sent them an online survey about how much media coverage they’d watched, and how they reacted emotionally. From the 80-some responses, McLaughlin says they learned that the children who already suffered from depression or anxiety were much more likely to develop PTSD symptoms after the bombing.

“We also found that children and adolescents who had previously experienced violence, particularly violence in their community, such as witnessing someone get mugged, seeing someone get shot, were also more likely to develop PTSD following the attack,” she says.

McLaughlin says that confirms previous studies suggesting that early exposure to violence makes someone more, not less, sensitized to violence later on. But McLaughlin is particularly excited about learning why that occurs. She says the kids whose brains had heightened amygdala response in the early study — and those tended to be kids with trauma histories — also were more likely to report symptoms of PTSD after the bombing. That told the researchers they may have found a physical marker in the brain that can help predict individual reactions to trauma — from terrorism to accidents to something more minor.

“And the more that we can understand the neurobiological markers as well as the psychological and social markers that make some children and adolescents at greater risk, the better able we’ll be to deliver early and effective interventions to prevent the onset of mental health problems,” she says.

A final finding of the study, McLaughlin says, has to do with media exposure to violence. The more the young people had watched coverage of the bombing, and the manhunt, the more likely they were to feel unsafe or under threat, and to develop mental health problems afterwards. She says this was true even among kids who did NOT have an apparent biological predisposition to stress.

“High exposure to media coverage of a terrorist attack is enough to increase their risk for developing mental health problem,” she says.

And while acts of terrorism cannot be controlled by parents, she adds, exposure to the media can. McLaughlin is now a professor at the University of Washington in Seattle. Her study on the marathon bombing is still under peer-review.