It’s normal, sometimes, to go back and double-check that you locked the door or the oven is turned off. But if a person suffers from obsessive-compulsive disorder (OCD), obsessive thoughts and compulsive behaviors become so excessive they interfere with your daily life.

OCD is an anxiety disorder characterized by uncontrollable, unwanted thoughts and repetitive, ritualized behaviors a person feels compelled to perform. They probably recognize that their obsessive thoughts and compulsive behaviors are irrational, but feel unable to resist them and break free.

OCD causes the brain to get stuck on a particular thought or urge—checking the stove 20 times to make sure it’s really turned off, or washing your hands until they’re scrubbed raw.