The Trump administration’s new policy of forcibly separating children from their parents will cause irreparable damage to many of the children and is a “great injustice,” doctors said Friday.

Medical groups are unanimous in denouncing the policy, which they note is not defined in any U.S. law. Besides being traumatic and unnecessary, the stress can damage brain development, they said.

“Any forced separation is highly stressful for children and can cause lifelong trauma, as well as an increased risk of other mental illnesses, such as depression, anxiety, and post-traumatic stress disorder,” said the American Psychiatric Association’s Dr. Altha Stewart.

“Many families crossing the United States border are fleeing war and violence in their home countries and are already coping with the effects of stress and trauma. These children deserve our protection and should remain with their families as they seek asylum.”

The Department of Homeland Security said Friday that 1,995 children were taken from their parents between April 19 and May 31 of this year.

It’s as bad and as harmful as seizing Native American children was in the past, said Dr. Colleen Kraft, president of the American Academy of Pediatrics.

“When you think about our history of separating our Native American kids and sending them to boarding school and Japanese internment camps, and other human rights violations, this is one that’s happening before our eyes and that’s why we need to speak out against it,” Kraft told NBC News.

Kraft saw some of the detained children in April.

“It was really devastating to see,” she said. “The first room we went into was a toddler room and there was a little girl who couldn’t have been more than 2 years old who was just sobbing and crying and was inconsolable.”

Staff told Kraft they were forbidden to physically comfort the children.

“And we all knew that the problem was her mother wasn’t there. And she wanted her mother. And none of us could fix that.”

As psychologists, we have documented multiple harmful effects of parent-child separation on children's emotional and psychological development and wellbeing and urge that the current policy of family separation be reversed." #FamiliesBelongTogether

Read the full letter below: pic.twitter.com/7K90VkMub4 — APA Public Interest Directorate (@APAPublicInt) June 15, 2018

It’s more than just distressing.

“We know that separation of children from loving caregivers promotes something called toxic stress in their brain,” Kraft said. “There are certain patterns of stress that result in disruptions of brain architecture in children and can result in young children in developmental delays.”

It can also cause physical symptoms, said Dr. Ana María López, president of the American College of Physicians.

"The lifetime impacts range from behavioral problems and mental health trauma to a person’s physiology," she said.

“It can raise the risk of chronic illness — cardiovascular disease and even cancer,” Lopez added. “From a health perspective this approach is really hurtful and damaging to families.”

Health specialists at the Johns Hopkins School of Public Health signed a letter saying the policy violates international conventions.

“These family separations violate the most widely ratified of all human rights conventions, the Convention on the Rights of the Child,” the letter, signed by the school’s dean Ellen MacKenzie, vice-dean Dr. Joshua Sharfstein and others, reads.

They dispute the administration’s argument that they are treating the would-be immigrants like they would any other criminals.

Separating parents and children at the border is bad for health and violates fundamental human rights, say APHA and @HealthyAmerica1 #FamiliesBelongTogether #SpeakForHealth pic.twitter.com/aBdkEKWwjj — APHA (@PublicHealth) June 15, 2018

“In fact, the administration is separating families who are following procedures to apply for asylum at the border, not having violated any law,” they said.

“Moreover, other families who have been detained after crossing the border are fleeing violence for a safer life and will seek asylum at the first opportunity to do so. These families have not committed a felony and should not be treated as threats to public safety.”

The Trump administration blames the policy of separating children from their families on previous Democratic administrations, a false assertion. There is no law requiring the separation of children from parents at the border.

Under the previous policy, children were usually allowed to stay with their parents in shelters while awaiting legal proceedings.

The American Academy of Family Physicians weighed in on the policy, also. "We stand with our fellow medical societies in urging the federal government to withdraw its policy of requiring separation of migrating children from their caregivers, and instead, give priority to supporting families and protecting the health and well-being of the children within those families," the group said.

“If you have a 2 year old crying for mommy, that is probably not a human trafficker.”

Border officials have also defended the policy by saying they’re worried about human trafficking.

“If you have an adult male and a teenaged girl, that probably makes sense,” said Kraft.

“If you have a 2-year-old crying for mommy, that is probably not a human trafficker.”