Researchers at the Montreal Neurological Institute and Hospital -- The Neuro -- have found nicotine cravings are stubbornly locked into our genes.

Their study has found people who have a fast "nicotine metabolism" -- meaning their bodies delivered nicotine to their systems quickly -- showed greater brain response to cravings.

So if your system sucks up the smoke stimulant slower, you're less likely to get the itch when you see someone else lighting up.

The research may lead to stop smoking programs that are tailored to a person's genetic code because you and the person puffing away next to you may metabolize nicotine differently, depending on an enzyme in the liver.

The researchers studied the brain scans of adults who smoked five to 25 cigarettes each day, for a minimum of two years.

Those with fast nicotine metabolisms had a greater reflex response to visual cigarette cues that gave them cravings.
"In other words, they learn to associate cigarette smoking with the nicotine surge," said clinician-scientist Dr. Alain Dagher, lead investigator at The Neuro.

"In contrast, individuals with slow metabolism rates, who have relatively constant nicotine blood levels throughout the day, are less likely to develop conditioned responses to cues."

For those people, smoking is not associated with nicotine surges. Researchers believe they may be taking up the habit for other reasons, such as stress release.

Dagher said smoking can have an impact on the enzyme, but adds it's mostly hereditary.

So feel free to blame your parents for your smoking habit -- no matter how much they warned you away from the habit.