Demi Lovato debuted a cute new blond bob this week, which was a pretty dramatic color change from the dark brown she'd rocked as of late. Lovato loves changing up her look, and in a visit to 'Ellen,' she revealed why her hair hue changes so often.

When Ellen DeGeneres remarked that Lovato's hair was much darker on her last appearance on the show, Lovato giggled, “It was a lot darker than this like, last week! ... I do this often," Lovato explained. "As you've heard I’m bi-polar. So I change my hair a lot!

DeGeneres had no idea about Lovato's struggle with the disorder, despite the 'Heart Attack' singer being open about her recovery and treatment (come on Ellen, don't play dumb). When DeGeneres asked what colors she's had previously, Lovato replied, "I've had black, brunette, red, like orangey red, pink and blue.”

Lovato also revealed why she travels with a pillow everywhere she goes -- and that she steals them from hotel rooms!