The federal government is considering opening tent facilities on military bases to house the swelling numbers of young people detained at the U.S. border with Mexico, including hundreds of children forcibly separated from parents accused of illegal entry. Since the White House instituted its policy of taking children away from parents, Chief of Staff John F. Kelly assured the public that “the children will be taken care of — put into foster care or whatever.” Even if that were true — facts remain scarce about the quality of care in the sprawling detention program, and the prospect of tent cities is unsettling — the children may already have been harmed by the separations alone.

As a clinical psychologist and neuroscientist at the University of Virginia, I study how the brain transforms social connection into better mental and physical health. My research suggests that maintaining close ties to trusted loved ones is a vital buffer against the external stressors we all face. But not being an expert on how this affects children, I recently invited five internationally recognized developmental scientists to chat with me about the matter on a science podcast I host. As we discussed the border policy’s effect on the children ensnared by it, even I was surprised to learn just how damaging it is likely to be.

At minimum, forced separation will cause these children extreme emotional distress. Most of us know this intuitively. Less intuitive, as Nim Tottenham of Columbia University told me, is that “the sadness is not the thing that really matters here. What matters is this is a trauma to the developing nervous system.” Extreme emotional responses to separation from parents is part of evolution’s plan to keep those parents close — to “break any parent’s heart,” as Megan Gunnar of the University of Minnesota said.