Selena Gomez announced that she is bipolar during an emotional online conversation with Miley Cyrus.
The 27-year-old singer said she "realised" she had the disorder during a recent visit to a hospital in Boston, Massachusetts.
During an appearance on Cyrus's Bright Minded live-stream on Instagram, Gomez said: "It doesn't scare me once I know it."
The star, who has been open about her battle with autoimmune disease lupus, also said she had undergone treatment for anxiety and depression as well as "other stuff that I've been dealing with".
Bipolar disorder, which used to be known as manic depression, affects a sufferer's mood, which can swing from one extreme to another.
Addressing how she has been self-isolating during the coronavirus pandemic, Gomez said she has been able to "use the tools that I've used in therapy" to cope.
"This is where we test each other. How are we gonna treat each other?" Gomez said.
"This can be a time to be gentle with ourselves. Taking breaks from the noise and even social media. Just being outside and breathing in."
Gomez, a former Disney child star turned chart-topping pop singer, told childhood friend Cyrus that speaking about her emotions helps her deal with them.
"I think talking through what you're feeling is extremely helpful," she said.
"Sometimes I have to feel it, sometimes I've got to cry it out and release it, and just take a deep breath."
She added: "I'm a big empath, so I feel so much of what the world is feeling. Being there for other people actually helps me, too."