The actress, who was diagnosed with Ocd as a young girl, reveals she came up with strange rituals after becoming obsessed with the number eight.
She tells Rolling Stone magazine, "I'd count eight times... I'd look on both sides of me eight times, I'd make sure nobody was following me down the street, I touched different parts of my bed before I went to sleep, I'd imagine a murder, and I'd imagine that murder eight times."
Dunham now takes anti-anxiety medications to help with her condition, but she admits the anti-depressants she took as a teen often had unpleasant side effects.
She says, "(I felt) drugged like a big horse. I was so exhausted all the time, night sweats. I was pretty fat in high school if I look at it, because it just slows down your metabolism. My mom would always be like, 'I think you're having a lot of side effects.' And I'd be like, 'You're such a b**ch; you just want me to be skinny!'"