Carey once thought she "had a severe sleep disorder," but later learned it stemmed from her bipolar II disorder. "It wasn't normal insomnia and I wasn't lying awake counting sheep. I was working and working and working. I thought working and promoting for days in a row without sleeping was just part of my life. 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," the mom of two says. Carey adds that she was inspired to tell her story after seeing people like Pete Davidson, Lady Gaga, Dwayne Johnson, Demi Lovato and Kevin Love speak about their mental illnesses.

"I'm just in a really good place right now, where I'm comfortable discussing my struggles with bipolar II disorder. I'm hopeful we can get to a place where the stigma is lifted from people going through anything alone. It can be incredibly isolating," the "Butterfly" singer tells the magazine. "It does not have to define you and I refuse to allow it to define me or control me."