Recent psychological science has both good and bad news about narcissism. I'll start with the good news. 

You may have heard that narcissistic traits are on the rise among young people, but the happy truth is that, while academics are still debating the finer points of the issue, it is pretty clear there is no massive uptick in narcissism--though reality TV and social media may sometimes make you suspect otherwise. 

But while claims of an epidemic of narcissism are generally overblown, business leaders in particular shouldn't stop worrying about narcissists in their ranks. The bad news is that both science and anecdotal evidence show narcissism, while ultimately destructive to individuals and companies, can help people get ahead professionally. Baseless confidence and a willingness to be ruthless are too often rewarded in the business world

Narcissism may not be more prevalent these days, but it's a particular issue for business leaders. Which is why entrepreneurs and executives should pay attention to a worrying new study that suggests narcissism is even more destructive than previously understood.  

Narcissists are even more destructive than you think. 

For the study a pair of Ohio State University researchers sifted through 437 previous studies on narcissism, which together looked at 123,000 individuals. We all know that narcissism makes people self-obsessed and callous, but does it also make them aggressive or even physically violent? 

A look at the huge data set gathered by the researchers provided a clear answer, and it isn't pretty. Here are the findings summed up by the study authors on The Conversation

Our review found that individuals high in narcissism are especially aggressive when provoked, but are also aggressive when they aren't provoked. Study participants with high levels of narcissism showed high levels of physical aggression, verbal aggression, spreading gossip, bullying others and even displacing aggression against innocent bystanders. They attacked in both a hotheaded and coldblooded manner. Narcissism was related to aggression in males and females of all ages from both Western and Eastern countries.

Or to put that in layman's terms, narcissists are true class-A a**holes. And as previous Harvard research has shown, firing your biggest office jerk will net you a bigger gain in profit than hiring a superstar. Narcissists are especially toxic (even more toxic than you may have realized) and toxic employees poison the performance of their teams. 

That makes it more important than ever for managers to avoid mistaking narcissistic charm for genuine ability. Experts in the space suggest that entails not taking bold claims at face value, but instead talking to a candidate's direct reports, fact checking their assertions and assumptions, and insisting they get into the details of their accomplishments in interviews.  

Is that harder work than just sitting back and allowing a fast-talking narcissist to charm you? Sure, but this latest research on just how toxic narcissists truly are should give you the motivation to put in the effort.