Lady Gaga has revealed she takes medication "every day for mental illness".
The singer, who admitted she became very depressed at the end of 2013, was performing at London's O2 Arena as part of her artRAVE: ArtPop Ball when she addressed the crowd.
During the show, she read an emotional letter from a fan who had attempted suicide, but had found comfort in her music, and then invited her on stage to sit with her when she performed Born This Way.
As she did, she reportedly said: "I take medication ever day for mental illness and depression and don't feel bad about it."
The 28-year-old said just six months ago she was in a dark place and didn't even know if she wanted to carry on with a career in pop.
Talking to Parade magazine, she said: "Six months ago I didn't even want to sing anymore.
"I tell Tony every day that he saved my life... I'm not going to say names, but people get irrational when it comes to money - with how they treat you, with what they expect from you... But if you help an artist, it doesn't give you the right, once the artist is big, to take advantage of them.