Demi Lovato has revealed she suffers with bipolar disorder.

The 'Sonny With a Chance' star - who said this week that she is quitting the Disney show - discovered she had the mental illness when she stayed in a residential Clinic for three months until January to be treated for an eating disorder.

Talking to People magazine, the 18-year-old singer-and-actress said: "I never found out until I went into treatment that I was bipolar. Looking back it makes sense. There were times when I was so manic, I was writing seven songs in one night and I'd be up until 05.30 in the morning. I feel like I am in control now where my whole life wasn't in control."

Shortly before her revelation, Demi publicly praised Welsh actress Catherine Zeta Jones for disclosing her Bipolar II disorder.

She wrote on micro-blogging website twitter: "I don't know Catherine Zeta-Jones personally but what she has decided to do it SO brave.. And SO difficult but worth it... I'm proud of her (sic)"