The trauma endured by children separated from their parents at the border — many of whom are fleeing chaotic or violent circumstances back home — will devastate them psychologically for years to come, experts say.

Thousands of immigrant children have been separated from their families since April, when the Trump administration put its zero-tolerance policy into place.

The policy calls for all unauthorized immigrants caught crossing the border to be criminally prosecuted. When that happens, adults are taken away from their children, who are put in detention centers and then shelters.

Inside those facilities, children are devastated: an audio clip published by ProPublica captures the sounds of children sobbing for their parents, begging to be allowed to call a family member.

"It is a form of child abuse," Dr. Colleen Kraft, head of the American Academy of Pediatrics, told CBS News after she'd spent time in a Texas facility where kids under 12 are being held.

Kraft said she was told staff members there weren’t allowed to hug or hold crying children at the facility to comfort them.

The no-hugging rule “paints the picture that we have lost our minds,” said Michelle Kinder, an expert in children’s mental health and executive director of Dallas’ Momentous Institute.

“What logical person is going to think — here is a child who by anybody’s standards is a victim,” Kinder said. "What is our mind-set that says we should not comfort them?”

The stress such children are likely under forces them into a constant fight-or-flight response, said Dr. Casey Call, assistant director of the Karyn Purvis Institute of Child Development at Texas Christian University.

“It’s like bathing their brain in toxins,” she said.

When children are distressed, they’ll naturally turn to a caregiver for comfort and support. But in a situation where they can’t find that comfort, they’ll remain in a state of chronic stress that “wears out all of your systems,” Call said.

The impact of that trauma, she said, will affect every part of their development, physically and mentally.

What’s worse is that the children arriving at the U.S. border to seek asylum are coming from already stressful environments, said Mark Reinecke, a psychologist at Northwestern University.

“These are youngsters who come to our border at risk. They come from stressful, chaotic, violent environments,” Reinecke said. “They come in with a predisposition, if you will, for emotional and social difficulties. And then they are separated from their parents.”

Juvenile detention centers, like the facilities the migrant children are housed in, can breed feelings of hopelessness, Reinecke said. Those types of centers are characterized by high levels of depression, anxiety and even suicidal thoughts in children.

The conditions of those facilities — good or bad — doesn't matter much when it comes to the psychological effect on the child, said Lee Gelernt, the deputy director of the ACLU's Immigrants’ Rights Project.

The organization is awaiting the decision of a federal judge on a class-action lawsuit to stop the practice of separating families and hold the government accountable for reuniting them. In the case, medical testimony shows that the trauma could last decades.

"What the medical testimony shows in our case is that the trauma comes from being separated from their parents," Gelernt said at a news conference Tuesday. "I just visited a family who was reunited after two months of separation. The mother said every night, the child asks if men are going to come take him away again."

Gelernt added that since children at a young age expect their parents to protect them from harm, the separation is "terrorizing these children."

Some children, Kinder said, will turn inward in the face of trauma. They might learn to believe that adults in their lives aren't there to take care of them, which could manifest as distrust of authority figures later on in life. Children have a naturally egocentric view of the world, Kinder said, so they might wonder: What did I do wrong?

Sometimes, kids dealing with toxic stress will have nightmares or they might regress developmentally. They could have difficulty forming relationships or keeping up in school. Down the line, they could develop behavioral problems like alcoholism and drug use.

Every interaction a child has with adults lays the groundwork for their identity and sense of self, so that doesn’t bode well for children in a setting where they’re reportedly not even allowed to be hugged, Kinder said.

“What we say to them, what we do, how we look at them, how we interact with them -- all of those interactions add up to a sense of self,” she said. “I can promise you that these interactions are laying neural pathways that are not positive.”

The good news is that children are resilient, but any time children are faced with trauma or stress that they can’t make sense of, “it has to come out some way,” she said.

As a scholar and a father, Reinecke said he sees a simple solution to avoid traumatizing children: keep families seeking asylum together.

He’s not alone in those beliefs. The American Academy of Pediatrics, the American Psychological Association and the American Public Health Association, among other professional organizations, have been clear in their statements: separating families at the border creates serious harm.

“This situation is at the same time tragic and completely avoidable,” Reinecke said. “It doesn’t have to be this way.”

Staff writer Samantha J. Gross contributed to this report.