Actress Tuppence Middleton has Obsessive Compulsive Disorder (OCD). It's not something she's really talked about before, except with a therapist. That is, until now. In this series, she's on a mission to find out more about the disorder - and herself - and to bust some myths along the way.

Today, she talks to screenwriter and author Rose Cartwright, who wrote her memoir 'Pure' after a ten-year struggle with 'Pure O'. What is Pure O? Why are the intrusive thoughts that come with it often violent or sexual? And why do so many people with Pure O suffer in silence?

Photo credit: Robert Harper. Producer: Becky Ripley.