WASHINGTON, April 8 (Reuters) - U.S. President Barack Obama called on Wednesday for an end to psychiatric therapies that seek to change the sexual orientation of gay, lesbian and transgender youth, the White House said.

The White House statement, written by senior adviser Valerie Jarrett, is in response to a petition calling for Obama to back a law to ban conversion therapy, which is supported by some socially conservative organizations and religious doctors.

The petition was started following the suicide in December of 17-year-old transgender youth Leelah Alcorn, who died after her parents forced her to attend conversion therapy, pulled her out of school and isolated her in an attempt to change her gender identity.

"The overwhelming scientific evidence demonstrates that conversion therapy, especially when it is practiced on young people, is neither medically nor ethically appropriate and can cause substantial harm," Jarrett said.

"As part of our dedication to protecting America's youth, this Administration supports efforts to ban the use of conversion therapy for minors," she said.

The petition said that on Sunday, Dec. 27, 2014, Alcorn wrote a suicide note, posted it on Tumblr and then walked in front of a semi-trailer. (Reporting by Eric Beech; Editing by Sandra Maler and Eric Walsh)