Everyone has things they do repetitively from time to time. You may feel that your hands aren’t quite clean, so you go back and wash them to your satisfaction. Or you may get in the mood to clean your house, even though you just did a thorough cleaning. These are normal behaviors, but people suffering from obsessive-compulsive disorder (abbreviated OCD) do them to the point where their lives are impacted, and others take notice of how often they perform these tasks.

Frequent thoughts are known as obsessions. The repeated behaviors and rituals are called compulsions. The symptoms of this disorder usually contain elements of both behaviors, but it’s also possible to have one or the other. It’s believed that roughly one-third of people who have been clinically diagnosed with obsessive-compulsive disorder also suffer from tics, which are sudden, intermittent and brief movements of a body part (usually the face) or uttering sounds.

More than 2 percent of the United States population aged 18 to 52 suffers from obsessive-compulsive disorder, according to statistics compiled by the National Institute of Mental Health. That’s approximately 3.3 million Americans who feel compelled to perform rituals or have unwanted thoughts that they believe they cannot control.

They may be inherited, and the tendency toward OCD can be observed in certain families. But researchers are still not sure why people are compelled in the way that they act, although they believe that certain parts of the brain control these actions. Add in that potential abnormality with stress and other environmental issues, and you have your classic obsessive-compulsive disorder.