The group's Task Force on Appropriate Therapeutic Responses to Sexual Orientation reached its conclusion after its review of 87 studies conducted between 1960 and 2007 and finding "serious methodological problems" in the vast majority of them.The full report can be read here at the American Psychological Association website.
Those few studies that did have "high-quality" evidence "show that enduring change to an individual's sexual orientation is uncommon," it said.
In addition, the report cited evidence that efforts to switch a person's sexual orientation through aversive treatments might cause harm, including loss of sexual feeling, suicidality, depression and anxiety.
This comes as no big surprise, really - you might have seen this documentary on the sad story of David Reimer: The boy who lived as a girl, or read the book version of his story: As Nature Made Him: The Boy Who Was Raised As A Girl.
Born as Bruce Reimer, he received gender reassignment surgery after a botched circumcision. Psychologist John Money coached "Brenda's" parents to try and raise "her" as a girl, and later used Brenda's case to support his pet hypothesis of Gender Neutrality... the notion that nurture could trump nature when it came to sexuality and gender identity. The result? Nature never gave way to nurture for Bruce/Brenda/David, and he suffered because of it. He died via self-inflicted gunshot wound when he was 38 years old.