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On Monday, when ProPublica released the now infamous seven-and-a-half minutes of audiotape recorded inside a U.S. Customs and Border Protection facility, in which several wailing kids can be heard crying out for their moms and dads, Darcia Narvaez clicked the link and told herself she’d do her best to listen to the whole thing.

Within seconds, however, Narvaez, a professor of psychology at the University of Notre Dame who specializes in parenting and child development, had hit the mute button. “I mostly read the captions,” says Narvaez. She can’t stand hearing children cry for prolonged periods of time without being comforted, she says, “because I know their brains are being damaged.”

Ever since the Trump administration’s recent statement that it had separated nearly 2,000 children from parents facing charges of illegally crossing the border—a number since raised to more than 2,300—troubling reports from inside the shelters where those children have been detained have proliferated. Many describe conditions in which, whether by official policy or not, shelter staff are prohibited or prevented from hugging or touching the detained kids—hundreds of whom are younger than 13 years old—to comfort them. Some testimonies, like the one from a former Tucson, Arizona, shelter worker, Antar Davidson (who quit last week because the shelter “didn’t have the trained staffing to handle the influx of younger, more traumatized children”), allege that even siblings in the shelters are prevented from hugging one another:

The breaking point for Davidson came, he says, when he was asked to tell two siblings, ages 6 and 10, that they couldn’t hug each other. “They called me over the radio. And they wanted to translate to these kids that the rule of the shelter is that they are not allowed to hug,” he says. “And these are kids that had just been separated from their mom—basically just huddling and hugging each other in a desperate attempt to remain together.”

Southwest Key, the nonprofit that operates several shelters along the U.S.-Mexico border including the one where Davidson worked, told NPR it has a policy of allowing hugs and comforting touches in certain circumstances. A South Texas shelter, meanwhile, told the American Academy of Pediatrics president Colleen Kraft when she visited (according to the same NPR story) that there was no federal regulation prohibiting workers from touching kids in their care. Still, what Kraft described witnessing in South Texas were staffers who believed they were not allowed to touch the kids to soothe them and behaved accordingly, and children who cried and cried yet were not physically comforted.

As anyone who’s ever witnessed a handoff to a babysitter or a drop-off at the first day of day care can attest, a hug or a snuggle from a sibling or trusted adult can be instrumental in relieving some of the anxiety, and even panic, associated with the departure of a parent. The research to confirm this goes far beyond anecdotes: According to decades of psychological study, positive touch from adults can not only lower stress levels in the moment, but can have long-term beneficial effects if administered regularly. And, relatedly, a consistent lack of positive touch has been shown to have detrimental effects on kids as they mature.

Tiffany Field, a professor of pediatrics, psychology, and psychiatry, founded the Touch Research Institute (TRI) at the University of Miami’s school of medicine in 1992. In the years since, she’s studied the effects of touch on kids in both traumatic situations (a 1996 study of kids whose families had been affected by Hurricane Andrew found that kids who routinely received back rubs from massage therapists saw significant improvements in their PTSD symptoms) and everyday situations (a 1999 study compared kids in Paris, “who get significantly more physical affection from their parents than kids in Miami,” to their counterparts in Florida and found they were less physically and verbally aggressive).

On some level, people know instinctively that caring touch makes them feel calmer. Much of TRI’s work over the past quarter century, though, has focused on what exactly happens in the body when humans are touched by other humans. According to Field, any activity that moves the skin stimulates the pressure receptors underneath it—which in turn increases the activity of the largest cranial nerve, the vagus nerve.

The vagus nerve has pathways to all major organs, Field says. “It slows down the heart. It goes to the GI tract and helps digestion. It helps our emotional expressions—our facial expressions and our vocal expressions. It enhances serotonin, the natural antidepressant in our system,” she says. “So that’s why hugging is good. That’s why massage is good.”

Plus, Field says, skin stimulation and the resulting vagal activity lowers levels of the stress hormone cortisol. High levels of cortisol are linked to a variety of health problems, such as anxiety, depression, cardiovascular disease, digestive problems, headaches, and sleep problems; additionally, elevated cortisol is known to harm the “natural killer cells” that help eliminate viral, bacterial, and cancer cells. In TRI studies, 10-week-old babies whose mothers massaged them regularly were found to get fewer colds and fewer bouts of diarrhea as they grew.

Elevated cortisol is also known to hamper the function of the hippocampus, the part of the brain that facilitates memory and learning; as a 2005 report from the National Association for the Education of Young Children notes, “children who sustain chronically high cortisol levels demonstrate cognitive, social, and motor delays in greater numbers than children with more normal levels of cortisol.” As a 2015 New Yorker story noted, when the researcher Mary Carlson conducted studies in the 1990s of children raised in Romania’s state-sponsored leagăne—institutional homes for small children that were erected to facilitate Nicolae Ceaușescu’s mandated baby boom—she found they reminded her of the socially deprived monkeys and chimpanzees she had studied in the past. The children, who were severely neglected and deprived of sensory and tactile stimulation, were characterized by “muteness, blank facial expressions, social withdrawal, and bizarre stereotypic movements.” They also had markedly elevated cortisol levels in their saliva.

Some regulation of professional caretakers’ affectionate touch toward children in their care is, of course, warranted. Adults working in schools, churches, youth sports leagues, and elsewhere routinely receive explicit instruction on what constitutes appropriate physical contact with kids. If authorities are preventing kids from receiving physical affection from caretakers in the name of protecting them from potential abuse, though, Field says, “They need to let the kids be physically affectionate to each other,” or at the very least, ensure they get exercise. Stimulating the pressure receptors under the skin through exercise, Field believes, can provide some of the same beneficial effects as getting a massage or getting a hug.

In one particularly harrowing scene in a Washington Post dispatch from the border, a shelter worker refrains from touching, hugging, or picking up a 2-year-old recently separated from her mother as she screams and pounds her fists on a mat. “We all knew what the problem was,” Colleen Kraft, who witnessed it, told the Post. “She didn’t have her mother, and none of us can fix that.” Certainly not, but the scene raises a compelling question: In this context, would a hug even help at all?

As Narvaez points out, for some children, it might not: A baby with stranger anxiety, for example, wouldn’t be much helped by even the friendliest stranger who wanted to console him. “It causes more stress, because the baby doesn’t trust them. They don’t smell right, they don’t feel right,” Narvaez says. And to some older kids with a more complete grasp of how the Trump administration’s policies are being enforced at the border, the offer of a hug from a shelter worker might seem downright offensive. The problem, of course, isn’t merely the lack of physical touch, but the fact that the practices in place separate children from their parents.

One of Field’s prevailing theories, though, which is supported by much of her research on the physiological benefits of touch, is that in many contexts, touch does not have to take place within an affectionate social bond to be effective. In other words, a person does not have to love you for their benevolent touch to have some therapeutic effects, and the lack of affectionate touch more generally can be harmful, regardless of whether those withholding the affection are relatives, caregivers, or other professional staff. If Field’s theory holds, it stands to reason that the placement of small children in an environment where they receive little to no physical affection is not just an unfortunate secondary effect of family separation, but a different form of cruelty entirely, being inflicted concurrently.

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