Demi Lovato has finally revealed the reason behind her stint in rehab. 

The Disney star-turned-singer, who recently announced she was going to put acting behind her in favour of a full-time music career, admitted to People Magazine that she suffers from bipolar disorder:

"I never found out until I went into treatment that I was bipolar."

18-year-old Lovato also tweeted a public message of support to fellow sufferer Catherine Zeta Jones, writing:

"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"

Talking about her diagnosis, the 'Here We Go Again' singer added:

"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 5:30 in the morning."

"I feel like I am in control now where my whole life I wasn't in control."

Watch the young star talk about her contribution to 'Love Is Louder: The Pressure To Be Perfect' here: