What provokes aggression and violence among peers? Often it’s scapegoating, in which children and teens are bullied by and in front of their peer group, leaving them excluded and humiliated. Several days after the Colorado shooting I was at a locked psychiatric hospital, interviewing a 17-year-old adolescent boy, Robert. He had put a gun to another boy’s head. As he described it, he lowered his voice so much that I could barely hear him.

“Put it to whom?” I asked.

“Put it to him, held it to his head.”

“How did you feel?”

“Strong. Powerful.” And then, “I ain’t never felt like that before.”

As it turned out, Robert hadn’t pulled the trigger, but he had held a gun to other kids’ heads several times. Why? I asked. Revenge, he said, to get back at kids who were picking on him.

Though boys who are unhealthy risk-takers often hurt others, girls usually turn their shame and anger on themselves, engaging in self-destructive behaviors such as cutting or extreme dieting. The same day I interviewed Robert, I received a phone call from the father of one of my patients. He was worried that his 17-year-old daughter, a self-styled, self-proclaimed Goth, was going to start cutting herself again, something she hadn’t done in six months. She told him that after the Colorado shooting, people kept mockingly asking her where her black trench coat was. “Those guys weren’t even Goths,’’ she said. “They were fascists, and even if they had been, why do adults assume one Goth is just like another? Or that one kid is just like another?” “I don’t,” said her father. He was doing the right things: paying attention to the potential danger signals, taking her seriously, asking questions and really listening to her answers.

Peers can influence risk-taking in both positive and negative ways. Kids get very concerned when they see friends taking bad chances. They don’t want to “rat” on them to adults, but they will still confide in an adult whom they trust when they suspect a peer is in trouble. However, a “toxic’’ best friend or group of friends can escalate bad behavior, especially where there is no adult input. Jim was 15 years old when several bullying boys took him onto the schoolyard and beat him up. Jim then struck up a friendship with another boy who had been similarly treated. They teamed up and started beating up younger children.

Years later, Jim told me in my office that he had longed to talk to his father about his new “best friend” and what they were doing. He had really hoped his father would ask why he had bruises on his face, or cuts on his hands. But his father never did ask, and Jim didn’t know how to begin that conversation.

Most kids don’t give such obvious signs that they are heading for trouble, but parents can detect other, subtler clues that a friend or peer group is leading their child astray. Often they’ll undertake new risks together, such as petty theft or lying. What can you do about it? Discouraging contact with such friends can backfire, provoking rebellion and bonding the buddies even more closely together. The best strategy is simply to increase your own contact with your teen. Conversely, if a new friend or group is becoming a positive influence on your child, you may see an increase in healthy risk-taking, such as going on camping trips or even bungee jumping.

Parents and other adults should encourage young people to take those kinds of chances, to help them grow and learn to assess danger. Even things as benign as running for school office or attempting a new creative activity carry with them the possibility of failure, so elders must be ready to offer them support and consolation. Adults also need to examine our own risk-taking patterns–kids are emulators, and they are watching us. Ultimately, teenagers, risk-takers all, need to be taken seriously. We have to keep asking the right questions–and listen when our children answer.