A personality disorder (PD) or character disorder is a type of disorder where a person thinks, feels and behaves differently from how society expects them to. Where these traits would be flexible in most people, these traits are rigid and unworkable in someone with a personality disorder and create lasting patterns and often lasting problems. These thoughts, feelings and behaviours can cause problems for the person, and for other people around them. In the United States, the United Kingdom, and many other countries, personality disorders are classed as a kind of mental disorder and are treated by medical professionals. About ten percent of adults have PDs. They are often caused by child abuse and trauma.