Due to a fragile ego, it is perhaps not surprising that narcissists have a tendency to lash out. But now with the aid of a meta-analysis (Kjærvik, S. L., & Bushman, B. J. (2021) as cited in APA, 2021), the statistics and link between aggression and narcissism have become clearer.
In an analysis of 437 studies involving more than 123,000 participants, the authors of the meta-analysis found that narcissistic behavior was associated with a 21% increase in aggression and an 18% increase in violence. The link between serious violence and more minor forms of violence was equivalent.
One surprising finding is that the degree of narcissism was not linked proportionately to aggression and aggressive acts. In other words, it didn't necessarily take pathological levels of narcissism to produce aggression. What seemed to produce the spark, was a provocation such as being ignored (not surprising considering the fragile egos).
Another interesting finding from the analysis was the nature of indirect aggression linked to narcissism which included spreading gossip and online bullying.
Symptomology
Narcissists have the belief that they are superior, perhaps deserving of special treatment. There is an old thought experiment that asks what happens when an unstoppable force meets an immovable object. Here we may stipulate the narcissist's self-belief as an unstoppable force, and when someone threatens that belief the consequences may be explosive.
Thus, narcissists are especially vulnerable to feelings (real or imagined) of humiliation, shame, and criticism. Thus one might imagine how these factors may be useful in interview techniques.
References:
APA, (2021) 'The link between narcissism and aggression' available at: https://www.apa.org/pubs/highlights/spotlight/issue-216 (Accessed 06/03/2022)