Mariah Carey has publicly revealed in a People cover story that she has been living with bipolar disorder.

The singer had been diagnosed in 2001 after the then-31-year-old had been hospitalised for a mental and physical breakdown while promoting her film Glitter and its soundtrack, which became the subject of intense media scrutiny at the time.

The singer "didn't want to believe" the diagnosis, she told the magazine's editor-in-chief Jess Cagle. She had initially thought she was suffering from a sleep disorder, "but it wasn’t normal insomnia and I wasn’t lying awake counting sheep."

"I was working and working and working … I was irritable and in constant fear of letting people down. It turns out that I was experiencing a form of mania. Eventually I would just hit a wall. I guess my depressive episodes were characterized by having very low energy. I would feel so lonely and sad — even guilty that I wasn’t doing what I needed to be doing for my career.”

“Until recently I lived in denial and isolation and in constant fear someone would expose me,” she told People. “It was too heavy a burden to carry and I simply couldn’t do that anymore. I sought and received treatment, I put positive people around me and I got back to doing what I love — writing songs and making music.”

Carey is now in therapy and medicated for bipolar II disorder. She suffers from periods of depression as well as hypomania, which is less severe than the mania associated with bipolar I disorder. The medication is "pretty good," Carey told the magazine. "It’s not making me feel too tired or sluggish or anything like that. Finding the proper balance is what is most important."