A 21-year-old lesbian in Utah said fake therapists subjected her to abuse and made her to wear a backpack full of rocks as part of her conversion therapy which, she said, turned out to cause more damage than cure.

Alex Cooper, a former Mormon, details her harrowing experience in her autobiographical book titled "Saving Alex."

Cooper says her parents sent her to a house owned by a couple in St. George in 2010 after she came out as gay.

The couple made her to stand against a wall carrying a backpack full of rocks.

"I did not know how many hours I had been standing there, quietly trying to manage the pain by shifting my weight from foot to foot," she writes, according to CBS local KUTV.

The couple told her as she stood at the wall, "Your family doesn't want you. God has no place for people like you in His plan."

They told her she was there because she was gay and they were trying to convert her to being straight.

"It's like sending you to therapy to change your eye colour," she told 2News. "It's not going to work. What it's going to do is damage you."

Cooper said while staying at the couple's house, she attempted suicide once and tried to escape several times.

One time, she said, the man at the home punished her.

"I came to my feet in front of him," she writes. "He made a fist and punched me in the gut, knocking the wind out of me. I doubled over and choked for breath."

The couple had no training or licence as therapists, according to Publishers Weekly.

The Church of Latter-day Saints denounced the practice.

"The Church denounces any therapy that subjects an individual to abusive practices. We hope those who experience the complex realities of same-sex attraction find compassion and understanding from family members, professional counsellors and church members," the church said, according to 2News and Raw Story.

She was finally allowed to attend Snow Canyon High School where she came in contact with the Gay-Straight Alliance that introduced her to lawyer Paul Burke.

"When she first called me, I was floored," Burke said, according to KUTV.

Burke represented Cooper in court where she won as the judge granted her right to live as a gay.

"The court order allowed Alex to live her life authentically. It allowed her to rebuild her relationship with her parents," said Burke.

Cooper said her mother apologised to her recently.

"They thought they were doing the best thing for me. I think that's what a lot of parents are under the impression of, that they're doing the best thing for their child," she said.

Cooper and Burke are campaigning to convince states to outlaw gay conversion therapy.