Narcissistic personality disorder (NPD) is a personality disorder derived from trauma, as all cluster B disorders are. It comes from extreme neglect and criticization in their childhoods, leading them to adapt to a certain survival instinct, and to shut down their emotions completely. People with NPD find it difficult to show empathy to others because of the lack of empathy they've been shown as children. They may have a sense of self-righteousness, and may defend themselves if they are in the wrong as a defense mechanism to past criticization.