In her pediatrics practice in Winston Salem, North Carolina, Julie Linton has seen several young patients who she believes are psychologically suffering from President Donald Trump’s tough stance on immigrants.

One 9-year-old boy came in with headaches, which Linton said started when “he was being told in school that his parents would be sent back to their country of origin.” Another patient, a 15-year-old girl, began experiencing panic attacks in crowds because she feared she would be separated from her parents.

“It comes down to two points: Parents are scared,” Linton said, “and children might not understand why their lives are in turmoil, but knowing their parents are scared makes them scared, too.”

In the past few days, Trump has shown his anti-immigrant rhetoric on the campaign trail was not just talk. On Wednesday, he issued an executive order that threatens to pull federal funding from “sanctuary cities,” or those that don’t turn over immigrants charged with minor crimes to the federal authorities. He also ordered the revival of a George W. Bush-era program that would step up the identification and deportation of undocumented immigrants, potentially sweeping up anyone who has simply signed a contract with an American employer.

“A nation without borders is not a nation,” Trump said on Wednesday. “Beginning today, the United States of America gets back control of its borders.”

When the orders were announced, the American Academy of Pediatrics issued a statement highlighting an unusual ripple effect of immigration crackdowns: They harm children’s health, potentially for life.

“Children do not immigrate, they flee,” said AAP president Fernando Stein in the statement. “Far too many children in this country already live in constant fear that their parents will be taken into custody or deported, and the message these children received today from the highest levels of our federal government exacerbates that fear and anxiety.”

The process Stein refers to is known as “toxic stress,” in which exposure to prolonged, unmitigated anxiety interferes with the development of children’s developing bodies and brains. While brief bursts of uncertainty are typically fine, exposure to unrelenting turmoil weakens neural connections just as they are beginning to form, as this video from Harvard’s Center on the Developing Child illustrates:

“The first two years of life is when rapid brain development occurs,” said Linton, who is also co-chair of the AAP’s immigrant-health special-interest group. “Over time, the prolonged exposure to this stress can limit the normal augmentation of synaptic connections because of potentially toxic chemicals.”

There are numerous studies showing both the immediate and lifelong effects of this stress overload. As Paul Tough described in his seminal New Yorker piece on adverse childhood experiences, early trauma can cause chemicals called methyl groups to attach to genes that govern stress-hormone production. The genes are disabled, making the brain less able to differentiate real threats from false alarms. The person remains on high alert, 24-7.

Toxic stress can change children’s behavior in different ways, Linton said. Toddlers might have trouble eating, sleeping, or going to the bathroom. Some children might develop temper tantrums, learning problems, or memory issues.

By unleashing a flood of inflammatory chemicals, stressful childhood experiences can also disrupt the metabolism and cardiovascular system, which is why people with stressful childhoods are more likely to be in poor health as adults, with higher rates of heart disease, diabetes, and depression. Children living in poverty have less brain surface area than those in richer families, as Madeline Ostrander reported, and young adults who grew up poor have more activity in the brain’s negative-emotion centers and less in the self-regulation portions. The more such adverse childhood experiences, the greater the likelihood of permanent disability, or even early death. Four or more “ACEs,” as they’re called, raise the risk of chronic bronchitis by 400 percent, and six or more mean a life that’s 20 years shorter than average.

The stress of potential deportation is not specific to undocumented immigrants in the U.S., but seems to spill over to all Latinos—even those who are born here. A study published this week found that both American-born and immigrant Latina mothers in Iowa were 24 percent more likely to have low-birthweight babies, a marker of poor health, immediately after a major federal immigration raid than the previous year. Thus, the sheer number of people who might be affected by this trauma is staggering. One in four children in the U.S. is Hispanic.

“Deportation is one of the most painful processes that a family can go through,” said Brent Wilkes, the national executive director of LULAC. “The United States may be the only country that many of these children know, so the fear of losing their home, their friends, and their sense of normality to return to an unfamiliar country is often jarring, to say the least.”

Immigrant groups around the country reported an uptick in harassment of Latino students in the aftermath of Trump’s victory. “Parents of children we are helping have told us that their children are terrified to go to school or even go outside because they fear they will be picked up and deported,” said Wendy Young, the president of the immigrant-aid group Kids in Need of Defense.

In Iowa, the situation became so bad that the ACLU and LULAC sent a letter to school superintendents urging them to protect immigrant families. A sample incident they cited involved a student being told by a peer, “I'm glad Trump won. Now all you Mexicans can go back to where you belong.”

Words hurt, of course, but they may become even more traumatizing now that they’re turning into actions.