Matt washes his hands over and over, until they're chapped and raw. Fern checks and rechecks the locks and light switches again and again before going to bed. Both have symptoms of obsessive-compulsive disorder (OCD), a disorder that affects three in 100 people.

"An obsession is an unwanted, unpleasant thought that intrudes on a person's mind," says Dr. Donald Black, professor of psychiatry at the University of Iowa College of Medicine and a staff physician at UI Hospitals and Clinics. "For example, a man may have a bad thought of losing control and stabbing his wife. Fortunately, most people with harmful obsessions never actually hurt anyone."

Types of obsessions include concern about harming others, being dirty, saving objects, and counting things. While there is no cure for this chronic disease, it can be treated, Black says. Antidepressants may reduce symptoms in many cases, and behavior therapy, a psychological treatment, may help others.

Most people with OCD hide it well, and family members may be the only ones who know. While obsessive-compulsive rituals, such as hand washing and saving things, can interfere with daily living, some people are able to hide the problem from co-workers by establishing some control over their need to complete the rituals.

Researchers do not know what causes the disease, but they believe it may be genetic or that it may be the result of a subtle, undetectable brain injury that occurs early in life. "OCD is a biological disorder and is not caused by bad parenting or stressful situations," Black says.

If you or someone you know experiences symptoms of OCD, contact your doctor or a psychiatrist.