A middle-aged man with obsessive-compulsive disorder (OCD) had, since early adulthood, a fear of being infected with the human immunodeficiency virus (HIV). In turn, he developed a variety of compulsive behaviors, such as excessive hand washing, to reduce what he perceived as risks for infection. Despite being aware of the irrationality of his behavior, his compulsions dominated his life. This type of scenario raises a question as to why some people with distressing thoughts develop excessive compulsions, while others do not.
Hauser TU, Eldar E, Dolan RJ. Neural Mechanisms of Harm-Avoidance LearningA Model for Obsessive-Compulsive Disorder?. JAMA Psychiatry. 2016;73(11):1196–1197. doi:10.1001/jamapsychiatry.2016.1938