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The brains of young adults who had stressful childhoods from abuse, neglect or poverty respond poorly to signs of potential risks or rewards, according to a UW-Madison study that could provide a biological clue to harmful behavior.

The young adults also made unwise choices during a gambling scenario and didn’t learn from their mistakes as much as others, said Seth Pollak, a psychology professor and senior author of the study, published Monday in the journal Proceedings of the National Academy of Sciences.

“They appear unable to use signs in the environment that things are not going to go well … so they continue to act and make decisions as if there aren’t warnings signs,” Pollak said.

The findings may explain why people with significant early life stress are more likely to engage in drug abuse, teen pregnancy, criminal behavior and other unhealthy activities, he said.

The results also suggest that punitive approaches to correcting behavior, often used by courts and the foster care system, might not be appropriate for people who develop a learning disability of sorts from childhood stress, Pollak said.

“We can’t assume they are responding to a punishment or a warning in the way other people might,” Pollak said. “It might not be that they’re choosing to ignore it. It might be that the information is not being encoded in the brain.”

The study, which also involved associate professor Rasmus Birn and senior research specialist Barbara Roeber, is a follow-up to research about stress hormones done at UW-Madison more than a decade ago in children ages 8 and 9.

For the new study, scientists brought back to the lab young adults from the earlier research — now ages 19 to 23 — who were among the most stressed or least stressed as children.

Many of those most-stressed as children were referred by the Dane County Department of Human Services. They experienced traumatic events such as parents killed by gunfire, parents arrested for prostitution and multiple foster home placements.

In the new study, participants underwent functional magnetic resonance imaging brain scans while engaging in a task meant to stimulate the reward centers of their brains.

First they saw a cue indicating that they might win or a lose a lot, or a little bit, of money — or nothing. Then a target randomly appeared, and they were told to press a button as quickly as possible.

The reward centers in the brains of the young adults with high levels of childhood stress lit up less in response to the cues. But when they lost money, a different part of their brains responded more.

“When something bad happens, they become over-reactive,” Pollak said. “That makes sense because clearly they weren’t expecting it.”

‘Against the odds’

In the gambling scenario, a computer randomly hid a yellow token behind one of a varying number of red boxes and blue boxes. Participants decided how much to bet on whether the token was behind a red box or blue box.

Even when most squares shown were red, increasing the odds the token was behind a red box, young adults with high levels of childhood stress often bet on blue. Their performance didn’t improve over time, as it did for the other group.

“They’re betting against the odds again and again,” Birn said in a statement.

It’s possible video games or smart phone apps could be designed to train people who endured childhood stress to pay more attention to warning signs of risks, Pollak said.

“If we can teach people math, and complicated math, we might be able to teach people to use these cues and search the environment and pay attention to things that might help them make healthier choices,” he said.