People who meet the criteria for personality disorders tend to show extreme and/or rigid personality traits. This behavior can lead to difficulties in social and work settings, as well as within interpersonal relationships. Personality disorder was once thought of as a problem that would define a person for life. However, current research reveals that it may be a condition that can improve with specific treatment. “If an individual meets the criteria for one personality disorder, and you assess them carefully, they often meet criteria for as many as four personality disorders,” says Yale Medicine psychiatrist Seth Axelrod, PhD.