"Resilience is not a trait that people either have or do not have," the APA says. "It involves behaviors, thoughts and actions that can be learned and developed in anyone."
Some of what Knight said Thursday indicates that the three did that together.
The most important part of resilience is to develop caring relationships, the APA says.
In court Thursday, Knight credited DeJesus -- whom she shared a dark room measuring about 7 feet by 11½ feet -- for saving her life.
"I never let her fall, and she never let me fall," Knight said. "She nursed me back to health when I was dying from his abuse. My friendship with Gina is the only good thing to come from this situation."
She returned the favor, at a cost to herself.
She placed herself in between Castro and DeJesus, taking on physical and sexual abuse herself to protect her friend, Ochberg testified.
Being the oldest, Knight often served as doctor, nurse and pediatrician for Berry and her young child. She acted as the midwife, when it was born, delivering Berry's baby in a plastic swimming pool.
Look to the future
It is important to see a horrible situation as something you will get out of, the APA says.
Somehow, Knight, Berry and DeJesus kept hope. As Knight said, "We said we'll all get out alive some day and we did."
She has said that she wants to make a life helping others who have been in her situation. She wants them to "know that there is someone out there to lean on and to talk to."
"I'm looking forward to my brand new life," she said in a statement.
The pain does not simply disappear, the APA says. It recommends writing about the feelings and thoughts attached to the trauma. The women kept diaries on their torments.
It also recommends spiritual practice. Knight has turned to her belief in God to find comfort.
"Emotional pain and sadness are common in people who have suffered major adversity or trauma in their lives. In fact, the road to resilience is likely to involve considerable emotional distress," it advises.
"They have life sentences," said Ochberg of the girls' emotional state.
"I think they will -- with the love and support of the whole community -- they have a good chance to live a good life. But that doesn't mean that they'll ever be free of the damage that was done," he said.
While they're no longer locked up in the hell Castro built for them, it is still inside of them, and they may need to let some of it out.