Expanded definitions of psychopathology: Exploring concept creep in narcissistic personality disorder.

Narcissistic personality disorder (NPD) has arguably been subject to concept creep, a phenomenon according to which psychopathological concepts gradually expand over time. Such semantic shifts may lead to over-inclusive lay concepts of mental disorders, which blurs the boundaries between mental health and illness. To assess the individual concept breadth of NPD and to test whether specialized knowledge in psychology reinforces or inhibits expanded concepts, a convenience sample of 414 participants primarily consisting of students from a Swiss university completed a vignette-based online-survey. The vignettes were based on DSM-5 criteria of NPD and varied alongside two dimensions that assess vertical (severity gradient, including non-pathological manifestations) and horizontal (variety of features, including normal behaviors) concept breadth. We found that about a quarter of the participants endorsed expanded concepts of NPD that incorporated non-pathological manifestations and normal features. An academic background in psychology was associated with less expanded concepts of NPD, both vertically and horizontally, whereas a conservative political attitude was associated with more expansive vertical concepts. Both vertical and horizontal concept breadth correlated with the self-reported frequency of perceiving narcissistic people in everyday life. We conclude that a substantial portion of young adults endorse expanded and over-inclusive concepts of NPD, which may affect their perception of narcissistic people in everyday life. Psychology students endorsed less expansive concepts due to a general reluctance to attribute the depicted features, even diagnostic core features, to a narcissistic personality disorder.