Obsessive–compulsive disorder (often shortened to OCD) is a mental disorder that causes repeated and unwanted thoughts and/or feelings (obsessions) and actions (compulsions). Anxiety is one of the most common symptoms and can lead the person to believe that if a task is not completed, something bad will happen. Such a task may be washing hands many times, keeping the lights on or even keeping their surrounding clean. This belief leads to more anxiety and tension. The actions that someone takes to stop the thoughts and feelings can take more than an hour every day. OCD can limit one's ability to take part in relationships, the workplace, and in society in general. OCD affects around 1.2% of the world's population, and it affects the lives of around 15%. In the United States, about one in fifty adults has OCD.