An obsession is a thought, impulse, or image that appears in someone’s mind and causes that person severe anxiety or distress.
Obsessions are the hidden part of OCD because no one but the OCD sufferer can experience the obsessions or the turmoil that the obsessions generate. Not only can others not witness the obsessions, but additionally, the individuals experiencing them often do not want to share their obsessions because of their disturbing nature.
Let’s take an example: Imagine walking down the street, stepping on a crack, and remembering the old saying “step on a crack and break your mother’s back.” Most people would just ignore this or recognize it as a meaningless saying. A person with OCD, however, may start to think about the saying and wonder why someone would say such a thing. Could it be because it is true? Could stepping on a crack really break my mother’s back?
This thought might play over and over ceaselessly in the person’s head, and as it does, the person will start believing more and more that it could be true and thinking how horrible it would be.
People with OCD give their random thoughts a lot of credence, and they start to imagine greater and greater probabilities that the things they fear might actually happen, despite the true probability of their happening. They can recognize that their thoughts are illogical, but they feel overwhelmed by them. As their fear of a thought increases, they increasingly attempt to somehow get rid of the thought.
One way people with OCD attempt to get rid of a thought is to suppress it, they tell themselves not to think of it, or they just try to ignore it. Unfortunately, this is often as unsuccessful as trying to get a song out of your head that you have been singing all day by trying not to think about it.
Therefore, they may also try to actually do something to get rid of the obsession, enter the compulsion.