<Tr> <Td> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> </Td> </Tr> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> <P> Narcissistic personality disorder (NPD) is a personality disorder with a long - term pattern of abnormal behavior characterized by exaggerated feelings of self - importance, excessive need for admiration, and a lack of empathy . Those affected often spend a lot of time thinking about achieving power or success, or on their appearance . They often take advantage of the people around them . The behavior typically begins by early adulthood, and occurs across a variety of social situations . </P> <P> The cause of narcissistic personality disorder is unknown . It is a personality disorder classified within cluster B by the Diagnostic and Statistical Manual of Mental Disorders (DSM). Diagnosis is made by a healthcare professional interviewing the person in question . The condition needs to be differentiated from mania and substance use disorder . </P>

What is the definition of narcissistic personality disorder