Tens of thousands of LGBTQ youth currently between the ages of 13 and 17 will undergo gay "conversion therapy" from a licensed health care professional, religious adviser or spiritual leader before they turn 18, according to a new report from the Williams Institute at UCLA School of Law.

The study's estimates are based on the Generations survey, a national probability study of lesbian, gay and bisexual individuals, and the U.S. Transgender Survey, the largest survey devoted to understanding the lives and experiences of transgender people.

Conversion therapy is a medically defunct practice that aims to change one’s sexual orientation or gender identity. Currently, talk therapy is the most commonly used therapy technique, the report notes, but some practitioners have also combined this with "aversion treatments," such as induced vomiting or electric shocks, the study explains.

The research estimates approximately 700,000 lesbian, gay, bisexual and transgender adults have undergone conversion therapy at some point in their lives, including about 350,000 who received treatment as adolescents.

It also estimates 20,000 LGBTQ youth currently between the ages of 13 and 17 will receive conversion therapy from a licensed health care professional before they reach 18, and approximately 57,000 will be subjected to the controversial practice from a religious or spiritual adviser.

“Our research shows that laws banning conversion therapy could protect tens of thousands of teens from what medical experts say is a harmful and ineffective practice,” Christy Mallory, state and local policy director at the Williams Institute and lead author of the study, told NBC News.

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California was the first state to ban the practice in 2012. Since then, eight other states and the District of Columbia have followed suit, including four — Connecticut, Nevada, New Mexico and Rhode Island — that did so in 2017. Mallory said more than 30 localities have also passed bans on conversion therapy, which, while not having the same reach as statewide laws, “sends a message.”

Mallory said she believes more states will adopt bans on conversion therapy. While a bill in New Hampshire recently failed to pass, another bill in Washington is making its way through the statehouse.

“We are seeing movement early in the legislative session in some sates, so I think that’s a sign that we could see more of these passed this year,” Mallory said.

The Williams Institute report found an additional 6,000 young people between the ages of 13 and 17 would have undergone conversion therapy, had their states not passed a law banning the practice.

Members of Congress introduced legislation at the federal level last year — the Therapeutic Fraud Prevention Act — that would classify conversion therapy, when exchanged for payment, as consumer fraud. If passed, the law would allows state attorneys general and the Federal Trade Commission to take action against practitioners of conversion therapy.

“Many professional health associations and the public support ending the use of conversion therapy on LGBT youth,” Mallory noted. “All these heath organizations are coming out against the practice, but we still see licensed health practitioners engaging in it."

These health associations that have spoken out against conversion therapy include the American Medical Association, the American Psychological Association, the American Academy of Pediatrics, the National Association of School Psychologists, the American Psychoanalytic Association and the American Counseling Association.

Mallory also noted public opinion polls are "showing that voters are against it as well."

A 2017 poll from Florida found 71 percent of residents believe conversion therapy on youth should be illegal, and a 2016 Virginia poll found 64 percent of residents feel the same way. In New Mexico, a 2016 poll found that 60 percent of residents support a ban on youth conversion therapy, and a 2014 national poll revealed only 8 percent of Americans believe conversion therapy could be effective at changing a person’s sexual orientation.

"I don’t think many people realize this is still going on," Mallory said of conversion therapy. "They may have heard of horror stories in the past, but with all the advances [in LGBTQ rights], they don’t think it is still something the LGBTQ community faces.”

Mallory said the Williams Institute report is the first of its kind to offer a national picture of the number of individuals who have undergone conversion therapy or are at risk of being subjected to the practice. She hopes the findings, especially the estimated number of LGBTQ youth who may be subjected to conversion therapy in the future, serve as a call to action.

“When you are talking about kids, it’s just a little different,” she said. “There’s just a natural inclination to protect kids.”

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