Calling someone a narcissist is one of those casual insults/compliments (depending on who you're talking to, right?) that is lobbed around frequently. But like many other mental health issues that get joked about, this one is based on a very real condition — one that hasn't changed its definition much over the past 20 years, and has, during that time, been consistently defined by the Diagnostic and Statistical Manual of Mental Disorders (DSM), the psychologist's big book of diagnoses.

People with Narcissistic Personality Disorder, as defined by the DSM-V (the most recent edition), need to display the following traits (abbreviated a bit; if you want to see the full definition, click here):

  • An exaggerated sense of their own self-importance
  • Puts quite a bit of energy and thought into fantasies of success, power or ideal love and romance.
  • Believes that they are special and unique (and should only associate with others who are similarly gifted)
  • Wants to be constantly admired
  • Acts in an extremely entitled way
  • Takes advantage of other people
  • Unwilling to empathize with other people
  • Is very envious of others or thinks they are envious of him/her
  • Displays rude or abusive attitudes and behaviors toward other people
Does this sound like anyone you know? While a classic narcissist will display all nine of these behaviors, having just five of them qualifies someone — though only a trained therapist can diagnose someone with the disorder. But seeing that narcissists aren't likely to recognize their own problem, many of them go unofficially diagnosed and untreated.

It's estimated that about 6 percent of the population has this personality disorder, and its more prevalent in men than women. The traits of this disorder get stronger as people age, and are usually in full bloom in a person's 40s and 50s. Kids and teens can't really be diagnosed with this kind of issue since they are growing and changing so fast.

Like most personality problems, there are upsides to narcissism: These people are usually highly motivated and driven to achieve high levels of power. It's more common for CEOs and politicians to be narcissists, for example. And the most ego-driven, rude and and non-empathetic CEOs — the most narcissistic — make the most money, a study found. So it can (literally) pay to be a narcissist. They may not have any reason to change — or any desire to either.

And their public perception may be good: "'ve got this person who is quite charming, charismatic, self-confident, visionary, action-oriented, able to make hard decisions (which means the person doesn't have a lot of empathy)," Charles A. O’Reilly III, a management professor at Stanford business school said in a statement attached to the CEO narcissism study.

Meanwhile, the people who are in the same family as a narcissist can be severely affected, especially their children. Working with one isn't a pleasant experience either. Narcissists have impulse-control issues, and frequently verbally abuse those around them, mock people they see as inferior and/or treat them with disdain — actions that never made anyone feel good (or even OK) about themselves, ever.

It's probably a combination of biological predisposition and environment (how someone grows up) that makes a narcissist, psychologists now believe. And the treatment? Plenty of sessions with a psychiatrist trained in dealing with this disorder.

Starre Vartan ( @ecochickie ) covers conscious consumption, health and science as she travels the world exploring new cultures and ideas.

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