Many children occasionally have thoughts that bother them, and they might feel like they have to do something about those thoughts, even if their actions don’t actually make sense. For example, they might worry about having bad luck if they don’t wear a favorite piece of clothing. For some children, the thoughts and the urges to perform certain actions persist, even if they try to ignore them or make them go away. Children may have an obsessive-compulsive disorder (OCD) when unwanted thoughts, and the behaviors they feel they must do because of the thoughts, happen frequently, take up a lot of time (more than an hour a day), interfere with their activities, or make them very upset. The thoughts are called obsessions. The behaviors are called compulsions.
Sourced from the CDC