On Wednesday, Rep. John Lewis, D-Georgia, opened a series of speeches telling his fellow members of Congress that “as we stand here, a 5-year-old woke up in a cage. … She was taken from her parents, from her brothers and sisters, from all she knows and loves. … This morning, Mr. Speaker, that innocent little child is crying in a cage. And we stand here doing nothing.”

As a law professor who collaborates with doctors through a growing movement of medical-legal partnerships to help people living in poverty, I have seen firsthand how laws and policies can impact the life trajectory of a child. The best thing we can do for that child, and the thousands like her, is to reunite her with her parents immediately. Her lifelong health depends on it.

President Donald Trump’s executive order now limits the separation of immigrant children from their families, outlining a new policy “to maintain family unity, including by detaining alien families together where appropriate and consistent with law and available resources.” Many have decried this executive order as trading the policy of family separation for one of infinite family detention, which can also be extremely harmful.

As the debate continues, it is critical to the health of children separated from their parents that they be reunited right away. Those children have experienced significant trauma that can cause lasting physical harm. Hundreds of studies stemming from research by the U.S. Centers for Disease Control and Prevention and Kaiser Permanente affirm that adverse childhood experiences, especially where prolonged, can affect their health for the rest of their lives. We all experience stress and our bodies often respond by speeding up our heart rates and producing a stress hormone called cortisol. But when that stress becomes prolonged—and a child has been separated from the caring adult she trusts to help her through it—that response can become toxic.

Toxic stress affects both the architecture of the brain and the functioning of the body, damaging a person’s health over the course of their lifetime. Children who have been separated from their parents are at higher risk not only for poor mental health but also for lifelong chronic health problems, such as cancer, diabetes and heart disease. The American Academy of Pediatrics cited this connection between childhood trauma and lifelong health problems as one of the reasons it stands strongly opposed to the separation of immigrant children from their families.

Childhood trauma has also been linked to other poor outcomes, such as difficulty in school and incarceration. In New Mexico, for example, a study of youth locked up in the state’s juvenile justice facilities showed that they have experienced a lot of trauma. More than 86 percent had lived through four or more traumatic childhood experiences, such as abuse, neglect or separation from their parents. More than a fifth of the girls had experienced at least nine such incidents of childhood trauma. It turns out that many of the state’s incarcerated teens were in fact some of its most traumatized children. This trauma has already begun to take its toll, as these youth not only live behind bars, they also experience high rates of mental health disorders and substance abuse. Out of concern for this link between childhood trauma and incarceration, Raul Torrez, the district attorney serving New Mexico’s largest metro area in Albuquerque, decided to prioritize prevention of childhood trauma as a crime prevention strategy.

From the juvenile halls of New Mexico to the homeless shelters of Washington, D.C., I have collaborated with doctors to remove legal barriers to health for traumatized children. It is imperative that our legal systems—from criminal justice to immigration and beyond—account for the role that childhood trauma plays in lifelong health and legal outcomes and work to disrupt that fate.

The good news for the kids at the border is that we have an antidote. Once a child has experienced trauma, the presence and support of a parent gives her the best chance of getting through it without experiencing the harmful lifelong effects of toxic stress. In calling for immigrant children to be reunited with their parents, American Academy of Pediatrics President Dr. Colleen Kraft explained, that when children, after experiencing “something awful and stressful” “have that loving caregiver who can respond to their needs, they can calm down those stress hormones—they can help them become resilient.”

In our partnership with physicians and other healthcare providers at the Georgetown University Health Justice Alliance, I have seen the role that law can play in facilitating or hindering health.  When our housing laws are well-written and implemented so that families have safe, healthy and affordable housing, children can thrive. When our education laws are structured and carried out to promote self-esteem and equal opportunity, children can achieve. And when our laws and policies keep families together, children have a chance to grow into healthy, productive adults. The thousands of immigrant children who have already been separated from their parents need to be reunited with them as soon as possible. It turns out that parents are the best medicine.

Yael Cannon is director of Georgetown Law’s Health Justice Alliance Law Clinic, through which law students collaborate with Georgetown University Medical Center students and faculty to improve the health and well-being of children and families living in poverty.