Definition: Narcissistic Personality Disorder
(NPD) is a personality disorder in which an individual has an unrealistic sense of his own self-importance, expecting special treatment and taking offense when it is not given. It would be diagnosed when it makes a major impact on the individual's life, and may co-occur with other psychiatric disorders. Poor parenting is often blamed for causing the disorder, but there may be a genetic or biological basis as well. For more information, visit About.com Psychology.