Men who are full of themselves may be full of some health woes, too.

A study published this week in the journal PLoS One showed men who are narcissists produce unhealthy levels of cortisol.

Typically associated with stress, that's the same hormone that provides an energy surge but can also lead to high blood pressure, a weakened immune system and more abdominal fat, according to the researchers from the University of Michigan and the University of Virginia who did the study.

Narcissism is characterized by grandiosity, low empathy levels and a sense of entitlement, the researchers said. Narcissistic men, it turns out, release more cortisol — even when they're not in stressful situations.

"Narcissistic men may be paying a high price in terms of their physical health, in addition to the psychological cost to their relationships," said Sara Konrath, study co-author and U. of Michigan psychologist, in a written statement.

The study noted that "the level of narcissism is rising in American culture, and that narcissism tends to be more prevalent among males." It's a trait that includes "an inflated sense of self-importance, overestimations of uniqueness and a sense of grandiosity."

For the research, they measured cortisol levels in 106 undergraduate students, both male and female, using saliva samples. They looked at baseline levels of the hormone to determine the hypothalamic-pituitary-adrenal (HPA) axis levels during relatively stress-free times. Chronic HPA elevation, they noted, has "significant health implications, increasing the risk of cardiovascular problems."

They paired that finding with analysis of a 40-item narcissism questionnaire that measures multiple components of the personality trait. Exploitativeness and entitlement are counted as negative aspects, while leadership/authority, superiority/arrogance and self-absorption/self-admiration are considered "more adaptive, or healthy."

Narcissistic men pay a higher toll, Konrath told USA Today.

"They're at especially high risk because someone who admits they're stressed out is going to get help, but they're not likely to. There may be a cost to this jerkiness. It's a little sad they're a group that wouldn't get help if they needed it."

"Even though narcissists have grandiose self-perceptions, they also have fragile views of themselves and often resort to defensive strategies like aggression when their sense of superiority is threatened," said co-author David Reinhard of the University of Virginia. "These kinds of coping strategies are linked with increased cardiovascular reactivity to stress and higher blood pressure, so it makes sense that higher levels of maladaptive narcissism would contribute to highly reactive stress response systems and chronically elected levels of stress."

They found that the worst of narcissism is associated with higher cortisol in men, but not in women. There was no link between healthy narcissism and cortisol.

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