Mariah Carey has spoken for the first time about her struggle with bipolar disorder.
The US singer and actress revealed she was first diagnosed with the condition in 2001, and that she is now in therapy and taking medication for type two bipolar disorder.
Carey told US celebrity magazine People that, following her diagnosis more than 15 years ago, she "didn't want to believe it".
She said: "Until recently I lived in denial and isolation and in constant fear someone would expose me.
"It was too heavy a burden to carry and I simply couldn't do that any more.
"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."
According to the NHS, bipolar disorder is characterised by extreme mood swings, and includes periods of extreme highs and lows.
Carey, whose biggest hits include Hero, Without You and All I Want For Christmas Is You, said that the medication she is now taking is having a positive effect.
"It's not making me feel too tired or sluggish or anything like that," she said.
"Finding the proper balance is what is most important."
She said that she first thought she was suffering with "normal insomnia" as she could not sleep, and that she was "working and working and working".
The star said she was "irritable and in constant fear of letting people down" and that she later learned she was "experiencing a form of mania".
"Eventually I would just hit a wall. I guess my depressive episodes were characterised 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."