Gov. Jerry Brown has signed legislation that makes California the first state to ban a controversial form of psychotherapy that's aimed at making gay teenagers straight.

Effective Jan. 1, mental health practitioners are prohibited from performing sexual orientation change efforts - known as reparative or conversion therapy - for anyone under 18.

The therapies "have no basis in science or medicine and they will now be relegated to the dustbin of quackery," Brown said in a statement.

Mainstream associations representing psychiatrists and psychologists have relegated reparative therapy to crackpot status in recent decades. A number of mental health associations in California supported the legislation.

But some organizations and ministries continue to use counseling and prayer to try to help conflicted Christians rid themselves of unwanted homosexual inclinations. Gay rights activists have said the damage they inflict on individuals can be deep and lasting and can put youth at higher risk of depression and suicide.

"We're grateful to Gov. Brown for standing with California's children," the Human Rights Campaign said in a statement. "LGBT youth will now be protected from a practice that has not only been debunked as junk science, but has been proven to have drastically negative effects on their well-being."

The group called on other states to follow California's lead on the issue.

Conservative religious groups and some Republicans have argued that banning conversion therapy would hinder parents' right to provide psychological care for children experiencing gender confusion.

The California-based National Association for Research and Therapy on Homosexuality said in August that the bill was a case of "legislative overreach." They said Democratic state Senator Ted Lieu's claims of harm to children were based on politics, not research.

Lieu, who sponsored the bill, said the law will stop children from being psychologically abused.