A very different form of anxiety disorder is obsessive-compulsive disorder. Obsessions are involuntary thoughts or ideas that keep recurring despite all attempts to stop them, while compulsions are repetitive, ritualistic behaviours that a person feels driven to perform. Obsessive thoughts are often horrible and exceptionally frightening. One patient, for example, reported that “when she thought of her boyfriend she wished he were dead; when her mother went down the stairs, she 'wished she'd fall and break her neck'; when her sister spoke of going to the beach with her infant daughter [she] 'hoped that they would both drown'”. Truly compulsive behaviours may be equally dismaying to the person who feels driven to perform them. They often take the form of washing or cleaning, as if the compulsive behaviour were the person's attempt to “wash away” contaminating thoughts. One patient reported that her efforts to keep her clothes and body clean eventually took up to 6 hours of her day, and even then, “washing my hands wasn't enough, and I started to use rubbing alcohol”. Another common type of compulsion is checking: repeatedly performing a particular behaviour to make sure that something was or was not done in a certain way. For example, a person might feel compelled to check dozens of times whether the doors are locked before going to bed. In a more unusual case, a man became obsessed with the idea that he had run over someone while driving and spent an entire day driving up and down the same piece of highway trying to find the “body” of the person he was convinced he'd run over.

Anyone can experience mild obsessions or compulsions at times. Most of us have occassionaly been unable to get a certain song lyric out of our head or have felt that we had to walk so as to avoid stepping on cracks in the sidewalk. But in an obsessive-compulsive disorder, the obsessive thoughts and compulsive behaviour are of a more serious nature. For example, a man who checks his watch every five minutes when his wife is late coming home is merely being normally anxious. But a man who feels that he must go through his house every hour checking every clock for accuracy, even though he knows there is no reason to do so, is showing signs of an obsessive-compulsive disorder.

Since people beset by obsessions and compulsions often do not seem particularly anxious, you may wonder why this disorder is considered an anxiety disorder. Simply put, if such people try to stop their irrational behaviour, or if someone else tries to stop them, they experience severe anxiety. In other words, the obsessive-compulsive behaviour has developed to keep anxiety down to a tolerable level.

Reference:

1. Understanding Psychology: 3^rd Edition. Charles G. Morris.