Nearly 700,000 young immigrants will spend the next six months in limbo, waiting to see whether the Deferred Action for Childhood Arrivals (DACA) program, which allowed them to legally live and work in the United States, will get a lifeline or be allowed to expire—potentially sending them back to home countries they barely know.

Now that the Trump administration has said it plans to rescind these protections, their fate is up to Congress, which for the past 16 years has tried and failed to pass legislation like the DREAM Act. Adding some hope to the situation but also sowing chaos, President Donald Trump reportedly struck a deal last week with congressional Democrats to protect the undocumented immigrants known as “dreamers” and tweeted his support for the very people his own administration’s policy would place in jeopardy.

While this plays out in Washington, D.C., many DACA recipients worry about more than thwarted plans for a college degree or dream job: They are also raising children who were born in America. In the debate over the program’s future, those children are often overlooked, though their well-being hangs in the balance.

How do their lives change when their parents no longer have to be afraid they could be deported? New research from Stanford’s Immigration Policy Lab finds that these families see dramatic improvements in their children’s mental health.

About 4 million children born in the United States have at least one parent who is unauthorized. Research suggests that fear of separation is a significant source of stress for these children, but it is difficult to pin down how their disadvantages stem from immigration status as opposed to poverty, cultural barriers, or other factors common among unauthorized immigrants. And if you find a way to isolate immigration status as a cause, there’s another hurdle: finding a large sample of people who by definition are excluded from most surveys and are reluctant to identify themselves.

DACA presented an opportunity to overcome both of these limitations. First, my colleagues and I used data from Oregon’s Emergency Medicaid program, which offers pregnancy coverage to immigrant women who do not qualify for traditional Medicaid. (Estimates from California and North Carolina, which offer similar coverage, find that 90 to 99 percent of enrollees are unauthorized immigrants.) As U.S. citizens, the children born to these mothers were eligible for full-scope Medicaid, so they could be tracked through their medical claims.

Second, we took advantage of one of the DACA program’s criteria for eligibility: individuals born before June 15, 1981 are not eligible, while those born after are eligible if they meet the other criteria. Just before and after that date are nearly identical groups of mothers: women with no meaningful differences other than their eligibility for DACA. And because the cutoff date was arbitrary, DACA eligibility was as good as randomly assigned.

We narrowed in 8,610 children born to these mothers between 2003 and 2015, and looked for a range of mental illnesses known to be provoked by external stress, including adjustment disorder, acute stress disorder, and anxiety disorder.

Why were these so important? Imagine a child who can’t sleep, who is withdrawn and depressed, who doesn’t participate in school activities or who lashes out at teachers and other kids. Mental illness at such an early age can set the child on a path for a lifetime of challenges, from low education to dependence on welfare to poor physical health and substance abuse—personal struggles with high social costs. Childhood mental illness also accounts for the highest share of the nation’s pediatric health care spending, reaching $13.8 billion in 2011 alone.

Before DACA was introduced, the two groups of children, as you might expect, were diagnosed with these disorders at roughly the same rate. After DACA, a gulf immediately opened between the two groups on either side of the mothers’ birthdate cutoff: Among those whose mothers were eligible, the rate dropped by more than half, from 7.8 percent to 3.3 percent.

Looking at these numbers, it’s clear that policy choices have the power either to consign children of immigrants to the same disadvantages as their parents, or to lift them into the healthy trajectory that many other U.S. citizen children enjoy from birth. Policy shifts at the federal level can take a while to be felt on the ground, but DACA’s benefits were almost instantaneous in giving young children security and peace of mind.

As Congress wrangles over a legislative replacement for DACA, lawmakers should take into account the program’s broader impact, which may extend for decades and have life-altering consequences for America’s children. Providing more permanent protection to the millions of unauthorized immigrant parents who do not meet the current DACA eligibility criteria could equally promote the well-being of their children.

Image: Immigrants’ rights demonstrators march in protest of President Trump’s decision on DACA on September 7, 2017 in the Queens borough of New York City. Getty/John Moore