During her nearly six decades in showbiz, Faye Dunaway has earned a reputation as one of Hollywood’s most accomplished — and difficult — actresses. In Faye, a new HBO documentary about her life, the Oscar winner reveals the reason for her on-set outbursts: bipolar disorder.

“I worked with a group of doctors who analyzed my behavior, who gave me prescriptions for pills they thought would be good for me. And that helped,” says Faye, 83. “I don’t mean to make an excuse about it, I am still responsible for my actions,” she adds. “But this is what I came to understand. … It’s something you need to be aware of. You need to try to do the right thing to take care of it.”