DENVER — Smoking kills roughly 5 million people every year, but plenty of us still do it.

Breaking the habit is a big challenge for just about everyone, but according to a new study, women have a harder time quitting than men.

So why is that?

“I feel like I smoke more when I drive because I’m just sitting there,” says Jennifer Schmidt of Denver, a smoker of more than 10 years. “I feel like it’s an addition to whatever I’m doing.”

A new study suggests women have a harder time dropping the habit because a woman’s brain chemistry responds differently to nicotine than men.

The American Medical Association says Nicotine Replacement Therapy (NRT) may not be as effective for women than their male counterparts.

“I like to see the smoke you know,” Jennifer says. “It’s more than just the nicotine. It’s actually holding the cigarette myself.”

The AMA study suggests female smokers may benefit more from other types of treatment, including behavior therapies such as exercise, or relaxation techniques.

“People just differ. Men, women, old, young…withdrawal symptoms affect them differently,” says Dr. Amy Lukowski of The National Jewish Medical Center, who worries this study may be discouraging.

“I think it`s very risky to say Nicotine Replacement Therapy is not effective for women.”

Dr. Lukowski adds the key to quitting is finding what works for you.

“It is a comprehensive approach. Nicotine replacement therapy is not the end all-be all,” she says. “It’s that plus learning how to deal without tobacco in your life every day.

The Colorado Quit Line boasts a 33-percent success rate for its callers.

Representatives at National Jewish Medical Center say those who call the hotline are seven times more successful than those who try to quit on their own.

The hotline offers support and free nicotine replacement therapy for some smokers. Call 1-800-QUITNOW for more information.