Despite widespread opposition from medical and mental health organizations, tens of thousands of LGBTQ youth in the U.S. will be subjected to anti-gay conversion therapy during their lifetime, a new report estimates .

Released this month by the Williams Institute at University of California, Los Angeles, School of Law, the report estimates that 698,000 LGBTQ Americans between the ages of 18 and 59 have undergone conversion therapy at some point in their lives. About 350,000 of those received that treatment as adolescents.

The report also estimates that 20,000 LGBTQ youths currently between the ages of 13 and 17 will be subjected to conversion therapy from a licensed health care professional before they turn 18. An additional 57,000 will be subjected to the controversial practice from a religious or spiritual adviser before age 18.

The studys lead author, Christy Mallory, believes the results may surprise many Americans in the wake of marriage equality and other social strides made on behalf of the LGBTQ community.

I think many people do not realize that conversion therapy is still being used, particularly by licensed health care professionals, Mallory, who is state and local policy director at the Williams Institute, told HuffPost.

Conversion therapy, also called reparative therapy and ex-gay therapy, has been known to include methods such as talk therapy, electroshock therapy and even treating LGBTQ identity as an addiction, not unlike drugs or alcohol.

As Mallory points out, the figures seem particularly staggering in light of recent polls that found little support for the practice. A 2014 YouGov poll , for example, found that just 8 percent of Americans believed conversion therapy could effectively cure someone of their same-sex attraction. Similar polls, conducted by Gravis Marketing in Virginia and Florida over the past two years, yielded similar results.

In 2015, President Barack Obama called for an end to conversion therapy, and the practice has been explicitly discredited by the American Psychiatric Association and other leading medical associations.

Still, conservative Christian groups like the Family Research Council and the American Family Association have backed the practice. To date, only nine states California , Connecticut , Illinois , Nevada , New Jersey , New Mexico , Oregon , Rhode Island and Vermont and the District of Columbia have bans on conversion therapy in place.

Williams Institute officials hope their report will be a critical step in influencing more states to adopt their own bans on conversion therapy, especially since the practice heavily targets adolescents.

Most conversion therapy is happening early in the life course during adolescence or young adulthood and this is why working with families is so important, Kerith Conron, a research director at the Williams Institute, told HuffPost.

Given that four states Connecticut, Nevada, New Mexico and Rhode Island outlawed conversion therapy last year, researchers are optimistic the trend will continue.

Many more states have already introduced legislation to ban the practice this year, Mallory said. This issue is gaining momentum across the U.S. and more states will likely ban the practice in the future.

Read the full Williams Institute report on conversion therapy .