What are 'intrusive thoughts' (we all have them) and what has CBT for OCD got to do with a polar bear? People sometimes talk about being "a little bit OCD", but the reality of obsessive compulsive disorder is much more difficult than a tendency to line your pens up or be super tidy.  Ashley Fulwood talks to Dr Lucy Maddox about his experience of OCD and his journey towards recovery with the help of CBT, and Professor Paul Salkovkis explains what we do and don't know about OCD.