The documents above and below were produced by the Institute for Safe Families to coach parents through the particularities of the teenage brain.

Philadelphia health officials brought parents together with child-welfare and juvenile-justice workers Monday to talk about the new science of adolescent brain development. Ideas about how to best help at-risk young people are changing.

Chronic stress and stress-produced chemicals can interfere with normal brain development, according to Temple University researcher Laurence Steinberg. He says the stress health experts worry about more than peer pressure or too much homework.

"We're really talking about pretty severe stress exposure," he said "Including exposure to domestic violence, victimization and familial dysfunction. If we can focus on reducing stress early on in life, we may be able to reduce the number of kids who end up in the juvenile justice system."

Counselors work to teach teens resiliency, but Steinberg says perhaps more important are efforts to identify and limit stress in childhood before it can do harm.

Philadelphia health commissioner Donald Schwarz says experts are learning more about some "fixes" that don't work.

"Taking kids who have made a mistake and putting them all in one place only increases the chance that they are going to do something that isn't the best and wisest choice," Schwarz said.

He said how the care system responds to trouble in the teen years can change his or her trajectory.

"Thinking carefully about how we react to a limited act that's committed in adolescence, by an adolescent, and not overreacting," Schwarz said.

"If we ruin a kid's ability to go on to later schooling ... if we stigmatize that child or harm their chances to get a job, or we remove them from their community for an extended period of time, all of those things are potentially long-term harmful, and things that don't need to happen," he said.

Not all children who are exposed to violence or family dysfunction develop problems. Steinberg and colleagues spend much of their time trying to pinpoint the things in a child's life that help neutralize toxic stress. Steinberg calls them "protective factors."

New data can guide practical strategy

Martha Davis leads the Philadelphia nonprofit the Institute for Safe Families, which works to prevent family violence and child abuse. Her group wants to equip parents with practical strategies based on the growing information on the teen brain.

Davis said there are some of the basics that every parent and caregiver should know: "Experience shapes the brain. Having connection helps build the brain. What trauma does to he brain—and the potential for healing."

"The brain is not fully developed until the early 20s," Davis said. "The brain is not finished cooking at age 14. There's still lots of growing."

Researchers have discovered that the brain is "plastic" and young people experience brain growth spurts, too.

Davis said those insights help many people understand why teens might seem impulsive, or why they like exciting activities.

"They really need that to grow these parts of their brains that are being pruned," Davis said. "We help them with that. How can they do new and exciting things that are not dangerous?"