Today's college students are more narcissistic and self-centered than their predecessors, according to a comprehensive new study by five psychologists who worry that the trend could be harmful to personal relationships and American society.

"We need to stop endlessly repeating 'You're special' and having children repeat that back," said the study's lead author, Professor Jean Twenge of San Diego State University. "Kids are self-centered enough already."

Twenge and her colleagues examined the responses of 16,475 college students nationwide who completed an evaluation called the Narcissistic Personality Inventory test.

The standardized inventory, known as the NPI, asks for responses to such statements as "If I ruled the world, it would be a better place," "I think I am a special person" and "I can live my life any way I want to."

The researchers describe their study as the largest ever of its type and say students' NPI scores have risen steadily since the current test was introduced in 1982. By 2006, they said, two-thirds of the students had above-average scores, 30 percent more than in 1982.

Narcissism can have benefits, said study co-author W. Keith Campbell of the University of Georgia, suggesting it could be useful in meeting new people "or auditioning on 'American Idol.'"

"Unfortunately, narcissism can also have very negative consequences for society, including the breakdown of close relationships with others," he said.

The study asserts that narcissists "are more likely to have romantic relationships that are short-lived, at risk for infidelity, lack emotional warmth, and to exhibit game-playing, dishonesty, and over-controlling and violent behaviors."