Here is a simple look at a complex issue. A pattern where a person is haunted by intrusive, irrational thoughts, and tries to relieve and control the anxiety created by these thoughts with ritualistic behavior. For example, if a man thinks that germs are everywhere, then he may try to decrease his fear by increasing the number of times he washes his hands. The illness usually occurs before the age of 25. It can be sparked by psychosocial changes in life, such as leaving home for college, the military, or marriage, or later in life by menopause or a mid-life crisis.
Ideas cause feelings, which in turn produce behavior.
Change the idea, and you change the behavior. Therefore, the person is helped to explore the irrational ideas, which result in compulsive urges. For example, the person may believe that they must be perfect, can not make mistakes without something terrible happening, are responsible for preventing harm, need to have complete control, or that they are in continuous danger. If we have fewer neurotransmitters like serotonin, our mind thinks sluggishly and, therefore, has a hard time dismissing irrational thoughts. Increase these neurotransmitters, and one can more easily assess and dismiss false ideas.