A big ego can be important to someone angling for the corner office. But once a true narcissist is in that office, look out — eventually, the ugly traits of arrogance, manipulation, exploitation and self-centered behavior will emerge. And the early promise of true leadership rarely follows.

These are some of the musings derived from a University of Illinois review of 54 studies of narcissists produced during the last several decades. Researchers were testing the oft-repeated notion that narcissists make good leaders. Essentially, what they decided was that narcissists are good at getting leadership positions, but often fall short when it comes to on-the-job performance over time.

The study, titled “Narcissism and Leadership: A Meta-Analytic Review of Linear and Nonlinear Relationships,” says that the extrovert within the narcissist gives the job candidate a leg up on others.  But, the authors wonder, could it be merely the narcissist’s gift of gab that gives them the edge, “as opposed to extraverted characteristics such as dominance, self-confidence and self-promotion” which might actually serve both individual and company well in some cases?

While allowing that some narcissists can provide leadership in the breach simply because of their inflated sense of self-importance, the researchers note that several studies indicated that narcissist tends to rise to the top at an early age among others new to the enterprise who have but a superficial understanding of the narcissist’s true character. When such a person is leading a stable or positively performing company, the outcome can be a disaster.

For starters, “having a narcissistic leader has been associated with reduced group-level information exchange, which can prove detrimental to team performance,” the study said.

Further, the narcissist’s “pattern of resisting and devaluing others’ input (also) eventually has negative consequences” for the organization.

On the whole, the research team concludes that a dash of narcissism can contribute positively to a leader’s performance. But beware the full-blown narcissist.

“Individuals high in narcissism are more likely to be selected into leadership roles, and very high levels of narcissism are expected to hinder leadership effectiveness. This means that organizations should be wary of creating selection and promotion practices that cater to narcissists’ strengths (such as unstructured interviews); because … narcissists can be quite charismatic under conditions of minimal acquaintance.”