Narcissus, the physically flawless character of Greek mythology, wound up falling in love with his own reflection. It isn't a good role model, and for that reason it is an insult thrown around by amateur therapists even more often than "he has Asperberger's".

 In clinical terms, narcissism comprises at least two largely distinct patterns of behavior associated with different traits: Vulnerable narcissism is marked by excessive self-absorption, introversion and over-sensitivity, while grandiose narcissism is characterized by an extroverted, self-aggrandizing, domineering and flamboyant interpersonal style. 

A little narcissism goes a long way, but if you want to be president of the United States, some narcissism seems to be necessary. Psychologists at Emory University say that grandiose narcissism in U.S. presidents is associated with ratings by historians of overall greatness of presidencies, as well as high marks for public persuasiveness, crisis management, risk-taking, winning the popular vote and initiating legislation.

It isn't all balloon and ponies for narcissists, though. Grandiose narcissism is also associated with some negative outcomes, such as presidential impeachment resolutions, cheating and bending rules.

The analysis was led by Ashley Watts, a graduate student of psychology at Emory. "Most people think of narcissism as predominantly maladaptive, but our data support the theory that there are bright and dark sides to grandiose narcissism." 

Lyndon B. Johnson scored highest on markers of grandiose narcissism, followed by Theodore Roosevelt, Andrew Jackson, Franklin D. Roosevelt and John F. Kennedy.

Lyndon Johnson topping the grandiose narcissism scale is not a surprise to historians, but it will disappoint a lot of modern Republicans. Credit: TIME

"It's interesting to me that these are memorable presidents, ones that we tend to talk about and learn about in history classes," Watts says. "Only rarely, however, do we talk about most of those who had low ratings for grandiose narcissism, like Zachary Taylor and Millard Fillmore."

The researchers also found that presidents exhibit elevated levels of grandiose narcissism compared with the general population, and that presidents' grandiose narcissism appears to be rising over time.

"As the importance of television and other media has grown in presidential elections, this could be giving an edge to those with the attention-seeking, outgoing personalities associated with grandiose narcissism," said co-author Scott Lilienfeld, Emory professor of psychology.

Their analyses drew upon personality assessments of 42 presidents, up to and including George W. Bush, compiled by co-authors Steven Rubenzer and Thomas Faschingbauer for their book "Personality, Character and Leadership in the White House." More than 100 experts, including biographers, journalists and scholars who are established authorities on one or more U.S. presidents, evaluated their target presidents using standardized psychological measures of personality, intelligence and behavior.

For rankings on various aspects of job performance, the analysis relied primarily on data from two large surveys of presidential historians: One conducted by C-SPAN in 2009 and a second conducted by Siena College in 2010.

Lyndon Johnson's mixed presidential legacy reflects both positive and negative outcomes tied to grandiose narcissism, Lilienfeld says. "Johnson was assertive, and good at managing crises and at getting legislation passed. He also had a reputation for being a bit of a bully and antagonistic."

Franklin D. Roosevelt, he adds, was also a highly assertive, dominant personality, but not particularly antagonistic or impulsive.

"In U.S. history, there is an enormous variety in presidential leadership style and success," Lilienfeld says. "One of the greatest mysteries in politics is what qualities make a great leader and which ones make a disastrous, failed leader. Grandiose narcissism may be one important part of the puzzle."

Citation: Ashley L. Watts, Scott O. Lilienfeld, Sarah Francis Smith, Joshua D. Miller, W. Keith Campbell, Irwin D. Waldman, Steven J. Rubenzer, and Thomas J. Faschingbauer , 'The Double-Edged Sword of Grandiose Narcissism: Implications for Successful and Unsuccessful Leadership Among U.S. Presidents', Psychological Science 0956797613491970 DOI: 10.1177/0956797613491970. Source: Emory Health Sciences