Legislators in four states have passed laws this year targeting “conversion therapy,” the discredited practice of using therapeutic or spiritual techniques to attempt to change a person’s sexual orientation.

But so-called conversion therapy remains legal and unregulated in the vast majority of states. Hundreds of thousands of people have been subjected to it and thousands more could be subjected to the practice in the coming years.

Delaware lawmakers on June 7 approved legislation prohibiting conversion therapy for minors, and if Gov. John Carney (D) signs the bill, the state will become the fifth to ban conversion therapy this year and the 14th state to ban the practice. This year, laws that ban conversion therapy for minors have been enacted in Hawaii, Maryland, New Hampshire, and Washington. Nine other states have passed similar laws: California, Connecticut, Illinois, Nevada, New Jersey, New Mexico, Oregon, Rhode Island, and Vermont. Washington, D.C. has also banned the practice.

New York Gov. Andrew Cuomo (D) in 2016 issued an executive order prohibiting health insurers from covering so-called conversion therapy. The order prohibits any state-licensed mental health facility from using the practice on minors.

Proponents of the pseudoscientific practice, also known by euphemisms such as “reparative therapy,” claim that using psychological or spiritual interventions can change a person’s sexual orientation or gender identity. A report published in 2015 by the Substance Abuse and Mental Health Services Administration (SAMHSA), condemned conversion therapy for young people, and concluded that the practice is “coercive, can be harmful, and should not be part of the behavioral health treatment.”

Sam Brinton, head of advocacy and government affairs at the Trevor Project, told Rewire.News that conversion therapy practices range from talk therapy to physical aversion techniques. These can have devastating effects on LGBTQ youth.

LGB youth “who experience rejection from their families like conversion therapy are 8.4 times as likely to have attempted suicide as LGB peers who reported no or low levels of family rejection,” Brinton said. “The lasting harm of conversion therapy is commonly diagnosed as similar to PTSD.”

The practice of “conversion therapy” has been rejected by medical associations and mental health organizations including the American Medical Association, the American Academy of Pediatrics, the American Psychological Association, and the National Association of Social Workers.

Around 698,000 adults in the United States have received “conversion therapy,” including about 350,000 who were subjected to the practice as adolescents, according to a study by the Williams Institute. The study’s authors calculated the estimated number of people who have received so-called conversion therapy by examining data sets from surveys of lesbian, gay, and bisexual people and surveys of transgender people.

“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, said in a statement.

The Williams Institute study concluded that 6,000 LGBTQ youth between the ages of 13 and 17 would have received conversion therapy before they reached adulthood if their state had not banned the practice. The study estimated that 20,000 LGBTQ youth will receive conversion therapy from a licensed health-care profession before they reach the age of 18 in the 41 states that have not banned the practice.

Bills to prohibit the practice of conversion therapy on minors have been introduced in Arizona, Colorado, Florida, Idaho, Kansas, Kentucky, Maine, Michigan,  Minnesota, Missouri, Virginia, West Virginia, and Wisconsin.

Mallory told Rewire.News the passage of laws banning conversion therapy for minors will significantly reduce the estimated number of young people who will be subjected to the practice. “About 1,000 of the estimated 20,000 youth will be protected under the new state level bans,” Mallory said.

The Williams Institute will publish an updated report at the end of this year after each state legislature has adjourned.

Brinton told Rewire.News that legislation has largely focused on prohibiting licensed mental health providers from practicing conversion therapy on minors, because youth are limited in their ability to legally give consent while they are under supervision or guidance of an adult.

“The Trevor Project works to protect LGBTQ youth from conversion therapy because if we can protect youth when they are under pressure to receive conversion therapy we can hope they will recognize its harms and ineffectiveness by the time they are legally able to choose it,” Brinton said.

Some LGBTQ advocates have criticized similar laws for not going far enough and not addressing all of the ways in which conversion therapy is implemented. Conversion therapy is often offered by people who are not licensed professionals, putting those young people outside the reach of the law.