Narcissism is an important risk factor for both aggression and violence as an analysis of 437 studies showed that it is linked to online cyberbullying, as well as bullying offline.

The findings, published in the journal Psychological Bulletin, showed that the key component of narcissism is entitlement.

It also has two peripheral components — grandiose (those with high self-esteem) and vulnerable (those with low self-esteem).

The study found all of these components were linked to aggression.

"Individuals who are high in narcissism are not particularly picky when it comes to how they attack others," said researcher Sophie Kjaervik from The Ohio State University.

For the study, the team combined and analysed data from many studies to provide a comprehensive view of this research area.

In this meta-analysis, they examined data from 437 independent studies with a total of 123,043 participants.

People higher in narcissism were not only more likely to lash out in anger, but were also more likely to be "cold, deliberate and proactive" in their aggression.

They were more likely than others to be aggressive whether they were provoked or not, the study found.

But the risk for aggression was significantly higher when they felt provoked, such as being ignored or insulted.