- According to a 2010 review of studies published between 1980 and 2008, NPD occurs in approximately 1% of the population.
- Other sources confirm this prevalence, estimating that 1% to 2% of the U.S. population meets the diagnostic criteria for NPD, and could benefit from narcissistic personality disorder treatment.
- Research published in 2008, based on interviews with over 34,000 participants, suggests a higher prevalence of NPD: approximately 7% of respondents in this study reported symptoms that met the criteria for NPD.
- Consistent across studies is the finding that men are almost twice as likely as women to meet the criteria for NPD.
- Because some of the typical NPD personality traits may be age-appropriate in young children, this disorder is considered extremely rare in children and typically not diagnosed until the teen years or young adulthood.
- There is a high rate of co-occurrence between NPD and several other mental illnesses, including substance use diagnoses and bipolar disorders.

