Narcissistic personality disorder is among 10 personality disorders identified by the Diagnostic and Statistical Manual of Mental Disorders, 4th edition, also called DSM-IV. A personality disorder is described as "an enduring pattern of inner experience and behavior that deviates markedly from the expectation of the individual's culture, is pervasive and inflexible, has an onset in adolescence or early adulthood, is stable over time and leads to distress or impairment." About 1 percent of the population suffers from NPD, with 50 to 75 percent of that number being male. Narcissists rarely seek treatment, and if they do, they progress slowly. Usually they do not feel they have a problem.