Trump now claims migrant children will be reunited with their families. Here are the lifelong psychological consequences these kids face.

Detaining children and separating families can lead people to develop post-traumatic stress disorder (PTSD).

The experience of being detained increases risks for PTSD for anyone.

In a systematic review of research on detained asylum seekers — including children, adolescents, and adults — researchers found that detention was linked to high rates of PTSD. These rates varied, but grew more severe the longer individuals were detained.

The detainees in these studies were not generally forcibly separated from families. But the trauma of family separation further increases PTSD risk, according to the American Academy of Pediatric, since kids become more vulnerable to stress and trauma without their caregiver.

Plus, by the time many of the kids who reach the border end up in the hands of the Border Patrol or the Office of Refugee Resettlement, many have already experienced trauma.

Jodi Berger Cardoso, an assistant professor of social work at the University of Houston, has researched the mental health of unaccompanied child migrants (who had not been forcibly separated from parents). She found that those kids had experienced an average of eight traumatic life events — a clinical category that includes experiences like kidnapping, sexual assault, and witnessing violent crimes. About 60% of those kids met the criteria for PTSD and 30% for depressive disorder.

Detention and family separation also raise the risk of anxiety and depression.

Dr. Lisa Fortuna, medical director for child and adolescent psychiatry at Boston Medical Center, told Business Insider that the removal of a caregiver can create acute distress that harms a child's ability to cope and self-soothe, which can lead to depression and anxiety.

Detainment can also have this effect. In the aforementioned review of studies on detained asylum seekers, one study found that rates of depression and anxiety both exceeded 75%. Another study of asylum seekers of all ages in the US found that the longer someone remained in detention, the higher their rates of depression and anxiety.

That risk can be exacerbated when the experience of detention is especially traumatic. The nonprofit investigative journalism organization Reveal recently reported that in facilities where kids from the border have been held, children have been sexually assaulted, forcibly administered psychotropic drugs, had medical issues left untreated, and more. Most mental health conditions have their roots in childhood, meaning that these traumas could have life-long impacts.

Adult members of detained family units also report high levels of depression, anxiety, PTSD, and self-harm, since "[d]etention itself undermines parental authority and capacity to respond to their children’s needs," according to an extensive analysis of research by the American Academy of Pediatrics.

Keeping kids away from their parents can harm their developing brains.

Fortuna said the depression, anxiety, and PTSD that children experience when they are separated from caretakers can be especially harmful to vulnerable developing brains.

"What we find from a neurobiological sense is that the circuitry in the brain that is a fear response can be actually harmed," Fortuna said. In other words, the parts of the brain that manage fear responses — the amygdala and hippocampus —develop differently in traumatized children.

That can alter their emotional experiences for the rest of their lives, Fortuna explained, which raises risks for a variety of mental health problems as they get older.

Experts say that even a temporary separation can permanently transform these parts of the brain.

For that reason, Fortuna wrote in an amicus brief for an ACLU case that family separation can cause "irreversible harm" for children.

The trauma of separation and detention raise risks of self-harm and suicidal ideation.

Jail-like detention can trigger "self-harm, suicidal ideation, [and] suicide attempts," according to Laurie Heffron, an assistant professor of social work at St. Edwards University in Austin, Texas. Heffron works with immigrants and women who have experienced domestic and sexual violence.

In several studies included in the previously mentioned review of research on detained young asylum seekers, suicidal ideation became common in more than half of the children and adolescents studied. Between a quarter and a third of children and adults who had never previously engaged in self harm began to do so, the studies found.

Much of this research doesn't account for the additional trauma of forced family separation on top of detention, but it indicates that detention itself is harmful.

The National Academies of Sciences, Engineering, and Medicine released a statement Wednesday addressing the lasting consequences of the family separation policy.

"Most mental, emotional, and behavioral disorders have their roots in childhood and adolescence, and childhood trauma has emerged as a strong risk factor for later suicidal behavior," the statement said.

Research indicates that detention of families and asylum seekers will raise already high levels of psychological disturbance and psychopathology.

A study of refugee children in Britain found that asylum seekers had more than triple the average level of psychological disturbance, which means they'd been exposed to trauma and had trouble with emotional or behavioral regulation.

An Australian study of child and adult asylum seekers found "very high levels of psychopathology," a term for mental disorders. This trend was "attributable to traumatic experiences in detention and, for children, the impact of indefinite detention on their caregivers," the study authors wrote.

"What we know about folks who've experienced trauma is they need to feel safe," Heffron told Business Insider. "Currently we're doing the opposite of that. Not only are people not feeling safe emotionally because they're separated from their families, they're oftentimes not feeling safe physically because of the conditions of detention."

The effects of this significant trauma may ripple through to future generations.

"Historically when things have happened like this — from the literature — when you have this accumulation of trauma and you break up families, you have a direct negative impact on the children, the caregivers, and potentially intergenerational bad effects," Fortuna said.

Researchers have linked the experience of Native Americans who were pressured to relocate away from tribes and family groups in the 1950s to problems with substance abuse and depression. Depression and juvenile behavior issues persisted through the next generation as well.

In Australia, as many as 100,000 children from the Aboriginal and Torres Strait Islander people were removed from their families from the late 1800s through 1960s and placed with white families or in government institutions to assimilate them into majority culture. Data shows that people who were forcibly separated from their families as children were almost twice as likely to be charged with a crime as adults, 60% more likely to have alcohol use disorders, and more than twice as likely to have gambling problems.

Surveys found that the children of people who'd been separated from their parents in Australia had more than double the average risk of emotional and behavioral difficulties.

Because of these alarming risks (and others), a number of scientific institutions have come out against family-separation policies.

Regardless of what happens next, the trauma of the family separations that already happened will continue to affect kids and families. So warnings from scientific associations about these policies are still urgent.

According to the National Academies of Sciences, Engineering, and Medicine, "these family separations jeopardize the short- and long-term health and well-being of the children involved."

The Academies' statement went on to cite "a body of scientific evidence that underscores the potential for lifelong, harmful consequences for these children and based on human rights considerations."

Similar condemnations were issued by the American Academy of Pediatrics, the American Psychiatric Association, and the United Nations human rights office.

"The administration's policy of separating children from their families as they attempt to cross into the United States without documentation is not only needless and cruel, it threatens the mental and physical health of both the children and their caregivers," the American Psychological Association said.

Despite Trump's recent order, there are still many questions about what will happen to families at the border.

Family separation hasn't fully ended until the more than 2,300 children who've been separated from their parents are reunited with their families. Once that process starts, children have to be found and connected to parents, some who have already been deported. That could take a while.

Another complication is that the new executive order says the Trump administration will detain families together "where appropriate and consistent with law and available resources," but many immigration lawyers say that wording leaves the door open for continued family separation.

Plus, as of Thursday, there are still major questions about the status of the zero-tolerance policy. If it is still in effect, experts are unsure if Trump's recent executive order will stand.

According to a 1997 court settlement known as the Flores agreement, the government cannot keep children in detention for longer than 20 days. Trump's new order directs Sessions to find a way to amend the Flores settlement and detain families together indefinitely, essentially creating internment camps. So it's possible that a court could reverse this order. That would mean family separation could resume, unless the zero-tolerance policy is reversed or Congress settles on some sort of immigration reform package.