Defence Mechanism which explains "compulsions" in a patient with obsessive-compulsive disorder?

Three ego defence mechanisms of obsessive-compulsive disorder are isolation, undoing, and reaction formation.The role of defence mechanism isolation is to safeguards a person from anxiety-provoking impulses. Undoing is associated with a compulsive act that is carried out in an effo to stop or undo the consequences that the patient unreasonably foresees from a threatening obsession.Reaction formation involves evident patterns of behaviour and consciously experienced feelings and thoughts that are paicularly contrary to the underlying impulses.