OCD is a disorder characterised by intrusive thoughts and repetitive, irrational behaviours, for example an obsession with cleanliness leading to repetitive hand washing, or a fear that something terrible will happen if they don't check the door dozens of times, making leaving the house extremely difficult.
A common way of helping treat OCD is to expose people to something they consider threatening - for example, if their obsession is around cleanliness, they may be made to touch a toilet seat but then prevented from washing their hands. However, so-called 'exposure therapy' often only has limited success and compulsions can return in times of stress. This new research, published in the Proceedings of the National Academy of Sciences, may explain why memories about safety don't stick.