In the dying days of 2014, a 17-year-old transgender youth, Leelah Alcorn, wrote a suicide note, posted it on Tumblr and then walked in front of a tractor-trailer, tragically ending her life.

Leelah explained how her parents had forced her to attend "conversion therapy", pulled her out of school and isolated her in an attempt to change her gender identity.

Now President Barack Obama has responded to a White House petition calling for an end to all conversion therapies aimed at reorienting gay, lesbian and transgender youth.

The petition states that conversion therapies "have been documented to cause great harms and in this case, Leelah's death." It says that therapists that engage in the attempt to brainwash or reverse any child's gender identity or sexual orientation are "seriously unethical" and legislation is needed to end such practices. It has received nearly 121,000 signatures since it was published at the start of January.

An accompanying post entitled "Official White House Response", quoting President Obama, says: "Tonight, somewhere in America, a young person, let's say a young man, will struggle to fall to sleep, wrestling alone with a secret he's held as long as he can remember. Soon, perhaps, he will decide it's time to let that secret out. What happens next depends on him, his family, as well as his friends and his teachers and his community. But it also depends on us -- on the kind of society we engender, the kind of future we build."

The White House response explains that conversion therapy is as any practice that seek to change an individual's sexual orientation or gender identity. "Often, this practice is used on minors, who lack the legal authority to make their own medical and mental health decisions. We share your concern about its potentially devastating effects on the lives of transgender as well as gay, lesbian, bisexual, and queer youth," it says.

"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."

It states that as part of their dedication to protecting America's youth, the administration supports efforts to ban the use of conversion therapy for minors.

Several states have already taken steps to ban it. California, New Jersey and the District of Columbia have all banned licensed professionals from using conversion therapy on minors. Since last year, 18 other states have introduced similar legislation.

While a national ban would require congressional action, Obama's administration is hopeful that the clarity of the evidence combined with the actions taken by these states will lead to a broader action that this administration would support.

"This Administration believes that young people should be valued for who they are, no matter what they look like, where they're from, the gender with which they identify, or who they love," the White House response says.

The response was written by Valerie Jarrett who said in an interview that President Obama had been moved by Ms Alcorn's story. "It was tragic, but I will tell you, unfortunately, she has a lot of company. It's not the story of one young person. It is the story of countless young people who have been subjected to this."