How many states allow parents to try to forcefully change their child's sexual orientation or gender identity through conversion therapy? It turns out the overwhelming majority still do.

On Thursday, Illinois became the fourth state — after California, New Jersey, and Oregon — to ban conversion therapy for people younger than 18 after Gov. Bruce Rauner signed the legislature-approved measure into law. Washington, DC, also bans the practice.

Under Illinois's law, the state licensing board will discipline health providers who participate in conversion therapy for a minor. The measure also links conversion therapy to consumer fraud, the Huffington Post's Kim Bellware reported.

LGBTQ advocates — and the White House — have been calling on states to ban conversion therapy. Pointing to the medical evidence, advocates say conversion therapy is not only ineffective; it's dangerous.

Conversion therapy is not only ineffective; it's dangerous

Top medical organizations agree. The American Psychological Association, the World Health Organization, the American Medical Association, the American Academy of Pediatrics, the American Academy of Child and Adolescent Psychiatry, and the American Counseling Association have all issued statements against the practice.

A review of the research, released by the American Psychological Association in 2009, concluded conversion therapies are "unlikely to be successful and involve some risk of harm, contrary to the claims of [conversion therapy] practitioners and advocates." The review also stated that "same-sex sexual and romantic attractions, feelings, and behaviors are normal and positive variations of human sexuality."

But some parents continue to force the therapies on their children after they reject their child's sexual orientation or gender identity, which can lead to horrible mental and even physical health outcomes. Research by San Francisco State University found that LGBTQ young people who were rejected by their families, compared with those who weren't rejected by their families, were eight times more likely to attempt suicide, nearly six times as likely to report high levels of depression, more than three times as likely to use illegal drugs, and more than three times as likely to have unprotected sex.

So conversion therapy not only fails to change children's sexual orientation or gender identity, but the basis for it can also increase their chances of taking part in actually harmful behaviors. It's no surprise, then, that at least some states are trying to prevent it.