Image copyright Lady Gaga / Twitter Image caption Lady Gaga (sitting next to her mother Cynthia) during her visit to New York's homeless centre

US pop star Lady Gaga says she has been suffering from post-traumatic stress disorder (PTSD) since being raped at the age of 19.

She revealed her mental illness during a visit to a homeless shelter for young LGBT people last month.

In a TV interview about the visit, she said: "I suffer from a mental illness - I suffer from PTSD. I've never told anyone that before."

Lady Gaga, now 30, first spoke publicly about the rape two years ago.

She has since admitted she blamed herself and did not tell anyone about it for seven years.

'Deepest secrets'

Her interview with the Today Show, which was broadcast on NBC on Monday, is the first time she has talked about having PTSD.

During her visit to the Ali Forney Centre in New York, she told the homeless lesbian, gay, bisexual and transgender teenagers that her trauma helped her understand others.

"The kindness that's been shown to me, by doctors as well as my family and my friends, it's really saved my life," the singer said, after bringing presents to the astonished teenagers at the centre.

"Meditation helps me to calm down," she said, adding that she was struggling with her mental illness "every day".

Lady Gaga later tweeted: "Today I shared one my deepest secrets w/ the world. Secrets keep you sick w/ shame."

Image copyright Twitter Image caption Gaga paid tribute to the others she met during her trip to the centre

A tearful young person from the centre she visited said: "Lady Gaga's act of kindness today was a reminder that love still exists - and that there's still some for me."

On social media, her fans opened up with their own experiences in response.

"I remember how your music and your spirit got me through really hard times," one user tweeted back to the singer. "Now I'm 1723 days self-harm free."

"I have something to tell you. I also suffer from PTSD. This is the first time I say it too. I love you and I admire you so much," another replied.

What is PTSD?

Post-traumatic stress disorder is an anxiety disorder which can develop after a very stressful, frightening or distressing event, or a prolonged traumatic experience.

People naturally feel afraid when in danger, but the legacy of some traumatic events is a change in perception of fear.

They may feel stressed or frightened in day-to-day life.

It can be caused by any traumatic event - including military conflict, serious road accidents, natural disasters, sexual assaults, and muggings.

Sufferers typically tend to re-experience the event in flashbacks, avoid talking about it, have trouble sleeping, or experience a change in mood.

Lady Gaga is one of the world's most successful contemporary artists, with a string of hits across her first five albums. Her sixth, Joanne, was released in October.

Media playback is unsupported on your device Media caption Lady Gaga's new album titled "Joanne" was released in October

The star has long been an advocate for the LGBTQ community; campaigning for Hillary Clinton during the election and protesting outside Trump Tower when the results were announced.

Last week, she gave her backing to gay rights during Donald Trump's presidency, telling the BBC "we are going to do everything that we can to protect the social progress we have made over the last eight years".