(CNN) In a tweet Thursday, President Donald Trump described someone who would shoot up a school as a "savage sicko." At CNN's town hall on the Parkland, Florida, school shootings on Wednesday, NRA spokeswoman Dana Loesch described the gunman as "an insane monster" who is "nuts" and crazy." And at a White House briefing Thursday, the President again used the term "sicko."

The shooter, Nikolas Cruz , struggled with depression, attention-deficit hyperactivity disorder and autism, according to a 2016 Florida Department of Children and Families report. But having a mental health diagnosis does not mean he would become violent, many experts say. And although Trump has said he wants to focus on mental health to stop school shootings, calling Cruz a "sicko" doesn't help, those experts claim.

....immediately fire back if a savage sicko came to a school with bad intentions. Highly trained teachers would also serve as a deterrent to the cowards that do this. Far more assets at much less cost than guards. A "gun free" school is a magnet for bad people. ATTACKS WOULD END!

"When it comes to mental health, language really matters. This is not about being politically correct. It's about wanting to do everything we can to encourage people to get health treatment that works," said Ron Honberg , senior policy adviser with the National Alliance on Mental Illness

Getting treatment is a challenge for the majority of people. Though 25% of the world's population has at one time experienced a mental or behavioral disorder, the World Health Organization says, only 44% of adults with diagnosable mental health problems and less than 20% of children and adolescents get the needed treatment, according to MentalHealth.gov. Studies have shown that people do not get help, in part, due to the stigma

"Hearing language like this is a punch to the gut, particularly if we have a goal as a nation to increase access to mental health care," Honberg said. "This is about the worst thing you can do."

"How helpful is calling a black person the n-word? Not only is it disrespectful, it fans racism," said Pat Corrigan , a distinguished professor of psychology at the Illinois Institute of Technology who manages the National Consortium on Stigma and Empowerment . "Using such language when it comes to people with mental illness is the height of disrespect and the height of ignorance, as it reduces some hugely complex person down to a diagnosis."

Corrigan also points out that it's wrong for a politician to use someone like Cruz -- or Sandy Hook shooter Adam Lanza or any other school shooters -- to imply that someone with a mental illness diagnosis is more likely to be dangerous or violent.

"You have these people living on the streets, and I can say in many cases throughout the country, they are very dangerous and shouldn't be there," Trump said Thursday.

But studies show otherwise. The greater majority of people with a mental illness will never be violent, research has found; in fact, people with mental illness are much more likely to be victims of violence.

....If a potential "sicko shooter" knows that a school has a large number of very weapons talented teachers (and others) who will be instantly shooting, the sicko will NEVER attack that school. Cowards won't go there...problem solved. Must be offensive, defense alone won't work! — Donald J. Trump (@realDonaldTrump) February 22, 2018

"Countless studies have shown that if you were going to predict who is most likely to be violent, mental illness falls way down the list. Age, gender, ethnicity is a much greater factor, and we wouldn't lock people up based on these qualities," Corrigan said.

One of the solutions, Trump suggests, is to institutionalize more people with mental illness.

"Part of the problem is, we used to have mental institutions, and I said this yesterday, we had a mental institution where you take a sicko, like this guy, he was a sick guy, so many signs, and you bring him to a mental health institution," he said. "We've got to get them out of our communities."

Evidence shows the contrary , however. Locking up people with mental illness for a long time is counterproductive, studies have found. "The best care is not locking someone away in a hospital. It's done in the community, where you can have treatment that will help you get back to school or to work," Corrigan said.

The American Psychological Association cautions that it is important to keep gun policy and mental health policy in distinct categories.

"Science shows the most consistent and powerful predictor of future violence is a history of violent behavior, not a diagnosable -- or diagnosed -- mental illness. The mental health needs of the country are separate from the issue of mass shootings," association CEO Arthur C. Evans Jr. said.

"People with mental illness account for a very small portion of incidents involving gun violence, and research has shown that individuals with mental illness are no more likely to become violent than individuals without mental illness," he said. "Involuntarily committing people with mental illness will not address our public health crisis of gun violence."

were closed, said Violent murders by people with a mental diagnosis did not go up when large institutions in the United States and the UKwere closed, said Diana Rose , a professor of user-led research who studies mental health at King's College London. "You cannot solve the problem by locking people up. It is just nonsense, and it destroys lives and is a deep form of social control, rather than provide people the support they need."

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Rose said that calling the shooter a "sicko" is "insulting" and "mean-minded." She added that "it is almost impossible to predict, even if someone has a diagnosis, if they are going to be a risk" for violence.

"Evidence shows you would have to lock up thousands and thousands of people to prevent a very rare crime," Rose said. "It's a completely ridiculous solution."