Narcissistic personality disorder (NPD) is estimated to be present in 0.5% of the general U.S. population, but it is found in 2% to 16% of individuals seeking help from mental health professionals. Prevalence is notably higher in specific populations, including 20% of the military population, 17% of first-year medical students, and 6% of the forensic population. NPD typically manifests by early adulthood and may worsen in middle or old age. It is more commonly diagnosed in males, who account for approximately 75% of those diagnosed with the disorder.