A compulsion (also called a ritual) is a person’s attempt to get rid of an obsessive thought, impulse, or image. Continuing with the sidewalk example in the previous question, the person may try to go back to the sidewalk and walk over the crack, as a way to undo the previous act of stepping on the crack. Or the person may recite a prayer or a special saying over and over again, such as “I love my mother,” as a way to counteract the fact that, the person believes, he may have just broken his mother’s back. Often, once the compulsion is performed in what the person deems the right way, there is a sense of relief, and the person moves on and continues his or her day. As the OCD progresses, however, the periods of relief get shorter and shorter, and people who suffer from OCD engage in rituals more and more often.
A compulsion could also be a behavior or mental act that a person feels compelled to perform in a very strict fashion, even without the experience of an obsession. Some people may do things each day in a certain way because they believe that that is just the right way to do it, even though they may not be able to explain why, it just feels right. An example of this may be someone who straightens pictures on walls, even if that person is not at his or her own home. A picture being askew is disturbing to the person, and they may feel compelled to straighten the picture even at the risk of offending the person whose possessions he or she is touching. To the person suffering from OCD, that risk is worth taking to stop the discomfort of seeing a picture that is not hanging straight.
Compulsions are outward signs of OCD, outsiders can see OCD sufferers washing their hands, turning lights on and off, checking door locks, and so on. Yet OCD is not always external; mental compulsions can also occur, such as having to say a prayer the correct way a certain number of times to prevent punishment from a higher power.