People who are narcissistic have a grandiose sense of self-importance, a lack of empathy for others, a need for excessive admiration and believe that they're entitled to special treatment because they're important and unique.

These personality traits tend to lessen with age, but a new study shows they never go away. Children who are more narcissistic than their friends, will continue to be that way as adults.

That's what researchers at the University of Bern in Switzerland found when they analyzed the results of 51 longitudinal studies that measured participants' levels of narcissism over time. Most of the people participating were followed for decades.

Remember to prioritize yourself even if the narcissistic person in your life won't. Your needs are just as important, and it's not your job to fix them.

Over 37,000 people ranging from 8 to 77 years of age were included in the analysis. Fifty-two percent were female and 48 percent were male. Although one study was from China and another from New Zealand, the majority of participants were mostly from the U.S., Canada and Western Europe.

Three different types or styles of narcissism emerged:

  • People who exhibit feelings of grandiosity and superiority and have a strong need for admiration were identified as having agentic narcissism.
  • Those displaying arrogance, entitlement, callousness and low empathy were said to have antagonistic narcissism.
  • Neurotic narcissism is characterized by hypersensitivity and poor emotional regulation or control.

For the most part, the researchers found that all three types of narcissism lessened to some degree as a person aged from childhood into adulthood. The decline was small for agentic narcissism, but moderate for antagonistic and neurotic narcissism.

A person's level of narcissism didn't change much over time, however. Those who were more narcissistic than their peers as kids remained so as adults.

“These findings have important implications given that high levels narcissism influence people's lives in many ways — both the lives of the narcissistic individuals themselves and, maybe even more, the lives of their families and friends,” lead author Ulrich Orth, a professor of Developmental Psychology at the University of Bern, said in a press release.

The study makes clear that a person's narcissistic tendency is unlikely to ever go away completely, or even dramatically lessen. “This was true even across very long periods of time, which suggest narcissism is a stable personality trait.” Orth said.

It's estimated that one to two percent of the U.S. population are narcissists. It can be challenging if you're in a relationship with one. Insight Therapy, an outpatient mental health practice, suggests several ways to deal with living with a narcissist:

  • Accept them for who they are. It causes more unnecessary stress trying to persuade someone that believes they can do no wrong.
  • Stop focusing on them. Remember to prioritize yourself even if they won't. Your needs are just as important, and it's not your job to fix them.
  • Speak up for yourself. Don't expect them to understand, but if you'd like to maintain a relationship with this person, speak up for yourself.
  • Set clear boundaries. Be firm in establishing what behaviors you refuse to tolerate. Remember that you are in control of your life, regardless of how you're treated by them.
  • Find a support system. One of the best things you can do if you can't avoid the person is to strengthen your current relationships.
  • Recognize that a narcissistic person may need professional help. Narcissistic Personality Disorder is a mental health condition, but it's unlikely that the narcissist can see that. In any case, it never excuses threatening or abusive behavior.

The study is published in Psychological Bulletin.