A personality disorder is a type of mental disorder in which one has a rigid and unhealthy pattern of thinking, functioning and behaving. A person with a personality disorder has trouble perceiving and relating to situations and people. This causes significant problems and limitations in relationships, social activities, work and school.
In some cases, one may not realize that he/she has a personality disorder because the way of thinking and behaving seems natural to him/her. And one may blame others for the challenges he/she faces.
Personality disorders usually begin in the teenage years or early adulthood. There are many types of personality disorders. Some types may become less obvious throughout middle age.