Resolving to drop some extra pounds is a popular way to start the new year, but a bad relationship can also be weighing you down.

At a time when many people take stock of their finances, their health and career goals, the new year is also an opportunity to re-evaluate relationships -- with family members, partners, friends and social acquaintances.

And one of the most difficult relationships a person can have is with a narcissist.

There may be warning signs in a problematic relationship you've been ignoring for years.

The label "narcissist" was frequently heard in the past election year, and is often used to describe politicians or celebrities. But when does self-absorbed, egotistical behavior become a medically recognized problem requiring treatment? And can a person with a narcissistic personality ever truly change?

Let's first look at the characteristics that comprise the diagnostic criteria for narcissistic personality disorder (NPD). Such a person exhibits several of these traits:

-- Having a grandiose sense of self-importance

-- Expecting to be recognized as superior even without achievements that warrant it

-- Exaggerating their achievements and talents

-- Being preoccupied with fantasies about unlimited success, power, brilliance, beauty or the perfect mate

-- Believing that they are superior and can only be understood by equally special people

-- Requiring constant, excessive admiration

-- Having a sense of entitlement and an unreasonable expectation of favorable treatment

-- Expecting unquestioning compliance with their demands

-- Taking advantage of others to get what they want; being exploitative and manipulative

-- Lacking empathy; having an inability or unwillingness to recognize the needs and feelings of others

-- Being envious of others and believing others envy them

-- Behaving in an arrogant or haughty manner

There's a reason these attributes may sound familiar to the parents of a toddler or teenager. St. Louis-area psychologist and clinical director Tom Chida says that it's normal for children to show elements of narcissism as they grow and develop.

As we grow up, most people learn to grow beyond ourselves, he said. "But some people don't. They stay in that highly egocentric state."

Their overconfidence masks a fragile self-esteem. The slightest criticism provokes hostility and lashing out far greater than the perceived insult.

Malignant narcissists enjoy having control and power over other people. They enjoy exploiting people for their own advantage, Chida explained. These are dangerous people to have in your life, capable of great harm, aided by their lack of empathy. They are thin-skinned, controlling, power-hungry and unable to handle the slightest criticism.

The exact cause of NPD is unknown, but it's thought to be linked to either excessive pampering or excessive criticism in the parent-child relationship.

Having a personality disorder is different from suffering from a bout of depression or anxiety, which can be brought on by difficult circumstances. Personality takes years to form. So it can take years of therapy for a narcissist to attempt to learn new skills and behaviors, Chida said. That's not to say a narcissist is incapable of change. But the biggest obstacle to change may be his own psyche, which makes the narcissist unwilling to accept a problem within himself. The narcissist's fragile ego is so threatened by the notion that their manipulative behavior is problematic that they reject that idea altogether. They blame others for their problems.

The mentality is "as long as this is working for me, I presume we are all equally happy," Chida said.

If you realize you're in a relationship with a narcissist who doesn't recognize they have a problem or one who is uninterested in changing, Chida offered this straightforward advice:

Run the other way.

-- Need help? In the U.S., call 1-800-799-SAFE (7233) for the National Domestic Violence Hotline.