For young people exposed to gun trauma — like the students of Sandy Hook Elementary School in Newtown, Conn. — the road to recovery can be long and torturous, marked by anxiety, nightmares, school trouble and even substance abuse. Witnessing lethal violence ruptures a child’s sense of security, psychiatrists say, leaving behind an array of emotional and social challenges that are not easily resolved.

But the good news is that most of these children will probably heal.

“Most kids, even of this age, are resilient,” said Dr. Glenn Saxe, chairman of child and adolescent psychiatry at NYU Langone Medical Center. “The data shows that the majority of people after a trauma, including a school assault, will end up doing O.K.”