"She was not well; she was really very very very not well. I would say she was possessed although I’m not sure I believe in such things,” the singer told Dr. Phil McGraw.
“She ran a torture chamber. It was a torture chamber. She was a person who took delight and smile in hurting you.”
The “Nothing Compares 2 U” singer continued: “She used to make me say over and over again "I am nothing. I am nothing" while she was beating me. “
O’Connor said she ran away from home at 13, and her mother, Marie O’Connor, died when she was 19, Mail Online reports.
Last month, the singer spoke out about her ongoing mental health battles in a 12-minute video posted to Facebook.
In the footage, she explained she was currently living in a motel and was abandoned by her family as a result of her mental health struggles, CNN reports.
"People who suffer from mental illness are the most vulnerable people on Earth," she said. "You've got to take care of us. We're not like everybody."
She continued: “I have been wanting to go for two f***ing years. I’m a 5’4” little f***ing woman wandering the world for two years by myself.
“I’m now living in a Travelodge motel in the arse-end of New Jersey.
“[No one] except my doctor, my psychiatrist — who is the sweetest man on earth who says I’m his hero — and that’s about the only f**king thing keeping me alive at the moment. The fact that I’m his bloody hero ... and that’s kind of pathetic.”
A representative of O’Connor later posted an update on her Facebook page reassuring fans that the singer was currently in good care.
"Hi everybody, I am posting at Sinead's request, to let everyone who loves her know she is safe, and she is not suicidal," the post reads.
"She is surrounded by love and receiving the best of care. She asked for this to be posted knowing you are concerned for her.”