Obsessive-compulsive disorder (OCD) involves persistent, uncontrollable thoughts or impulses (obsessions), managed by performing physical or mental rituals (compulsions). Common obsessions involve contamination, fear of harming someone, moralistic thoughts, and unwanted sexual thoughts. These intrusive thoughts cause anxiety, disgust, or guilt. The distressing emotions trigger compulsion to engage in specific behaviors or mental rituals to reduce distress. Many people display low-level compulsive behavior, such as constantly checking their cell phone or keeping their house tidy. Obsessions and compulsions become a mental disorder when they interfere with normal functioning and reduce quality of life.
A common example of OCD is a fear of germs leading to constant hand washing or repetitive cleaning. Compulsive behaviors in OCD act as an emotional release valve that temporarily relieves the distress associated with the mental obsession. For example, a person may have an obsessive fear of setting their apartment on fire, which they manage by constantly checking the stove and the electrical sockets to make sure they are safe.
OCD has a clear biological basis—a person is four times more likely to have OCD if they have a parent or sibling with the disorder. Brain scans suggest that OCD is linked to overactivity in brain regions that detect problems, leading to a persistent sense of worry or dread. This makes it harder for a person to distinguish what is safe from what is dangerous. Both medication and learning new ways to cope with intrusive thoughts can lead to changes in brain activity.There are several disorders that share similarities with OCD. Trichotillomania involves obsessively pulling hair out of one's scalp, eyebrows, or other part of the body. Hoarding involves an inability to let go of physical possessions, including items others see as worthless (such as old newspapers or partially consumed food). Some people who hoard are also compulsive buyers who have multiples of the same item. Hoarding disorder can lead to unsafe and unsanitary living conditions and significant interpersonal difficulties. Body dysmorphic disorder involves obsessive attention to perceived body flaws. People with body dysmorphic disorder will sometimes undergo multiple cosmetic surgeries to correct flaws other people cannot see.