Short answers, pulled from the story.
Researchers Miller, Campbell, and Pilkonis published a study in Comprehensive Psychiatry in 2007 that distinguished grandiose individuals who display arrogance and social dominance from vulnerable individuals who show shame and hypersensitivity.
Heinz Kohut coined the term narcissistic personality disorder in 1968 to establish modern psychiatric definitions following earlier historical milestones like Ovid writing Metamorphoses in 8 AD.
A 2021 review revealed lowered gray matter volume in the medial prefrontal cortex among people with NPD while studies also identified structural abnormalities specifically in the left anterior insular cortex.
Critics characterized the new dimensional system as an unwieldy conglomeration of disparate models that cannot happily coexist despite the American Psychiatric Association retaining NPD in the Diagnostic and Statistical Manual of Mental Disorders Fifth Edition.
Overall prevalence estimates range from 0.8% to 6.2% according to epidemiological data found within the provided script text regarding population statistics.