"This therapy can be dangerous," said the bill’s author Sen. Ted Lieu. The Torrance Democrat added the treatments can "cause extreme depression and guilt" that sometimes leads to suicide.
Conservative religious groups emphatically reject that view of sexual orientation therapy and say the ban would interfere with parents’ rights to seek appropriate psychological care for their children.
The bill would prohibit so-called reparative therapy for minors and obligate adults to sign a release form that states that the counseling is ineffectual and possibly dangerous.
Representatives of the National Association for Research and Therapy of Homosexuality on Tuesday called the bill a piece of social engineering masquerading as a solution to a clinical problem.
David Pickup, who is registered with the California Board of Psychology, said a ban would prevent people from recovering from trauma of sexual abuse.
"Any therapist worth his salt knows that homosexual feelings commonly occur in victims as a result of abuses," he said. "I ought to know because I was one of those boys."
The debate comes as gay rights issues take the spotlight around the nation.
Over the weekend, Vice President Joe Biden said he is "absolutely comfortable" with same-sex couples getting the same rights as heterosexual couples.
In North Carolina on Tuesday, voters moved to define marriage as solely between a man and a woman. And in Colorado, a civil union bill faced a looming deadline in the state Legislature.
Conversion therapy penetrated the national consciousness last year when former Republican presidential candidate Michele Bachmann was questioned over whether her husband’s Christian counseling business provided services that attempted to change gays and lesbians.
Interest in the religion-based therapy appears to have surged in recent years, sparking debates about whether sexual orientation is an immutable characteristic.
Exodus International, the world’s largest Christian referral network dealing with homosexuality, now steers people to 260 groups across the country, up from about 100 a decade ago. The organization has 35 ministries and churches scattered around California, from the Central Valley to the U.S.-Mexico border.
Conservative religious leaders say it is important for families to have access to services as teens first awaken to their sexual orientation.
"When I was struggling with those things in the early ’80s, the church didn’t seem like it had a place for me," said Alan Chambers, president of Exodus International.
But mainstream mental health organizations say people should not be seeking out such ministries.
The American Psychological Association said in 2009 that mental health professionals shouldn’t tell gay clients they can become straight through therapy.
The association cited research suggesting that efforts to produce the change could lead to depression and suicidal tendencies, and stated that no solid evidence exists that such change is possible.
The American Counseling Association and American Psychiatric Association have also disavowed the therapy. The psychiatric association removed homosexuality from its list of mental disorders nearly 30 years ago.
Last month, the author of a widely-cited 2001 study supportive of the notion that "highly motivated" people can change their sexual orientation retracted his study and apologized to the gay community.
Peter Drake, 55, testified Tuesday that he sought out conversion therapy in an effort to save his 20-year marriage, and the years of trying to change himself nearly drove him to suicide.
"I am left-handed and I am gay," he said. "I could learn to write with my other hand, but that is not who I am."
Gay rights advocates say a ban like the one proposed in California could represent a turning point and inspire similar legislation in other states.
The measure, which moves to the full Senate, would likely face legal challenges from opponents who say it is unconstitutional.
"We’re talking about stepping into the doctors’ room or the physiatrists’ office and clamping a hand over the mouths of the clinicians," said Matthew McReynolds of the conservative-leaning Pacific Justice Institute.
Lieu says he addressed free speech issues in SB1172 by excluding clergy and other people who are not medical professionals from the legislation.
The practice has garnered attention in past years as teens sent by their parents to conversion therapy programs have shared their stories online.
Among the lawmakers who approved the bill Tuesday was Sen. Mark Leno, D-San Francisco. Leno said his parents sent him to a therapist when he first told them he might be gay, and it was only because the therapist did not pathologize his sexual orientation that he was able to come out of the closet.
"There are many that are trapped in this horror situation," he said. "And it can have extraordinarily negative impacts."