By Toronto Star

It started with a pack of Players stolen from her dad, who bought cigarettes by the carton to save money. Sasha Manoli knew where he kept them — in a kitchen cupboard. She snatched a pack on the day she decided to smoke. She was 14.

After meeting her friend, the teenagers went to Laurentide Park, which lies besides the Don Valley Pkwy. near York Mills Rd. It was winter. They went over to a pine tree and lay down under it in the snow. Manoli lit one cigarette and “half-smoked,” barely inhaling.

“I really remember the smell and the taste, but I can’t describe it,” she said. “But there was something very distinct.”

What Manoli didn’t know at the time was her decision to smoke may have had less to do with peer pressure and perhaps more to do with fate.

It’s an acknowledged theory in medicine that genes determine how quickly and how deeply people become addicted to smoking. Now researchers are looking for ways to personalize medicine to treat nicotine addiction so that everyone, even people who have a genetic predisposition to smoking, can quit.

Although peer pressure often propels teens to start smoking, Rachel Tyndale, a biochemistry professor at the University of Toronto, says your genes may determine whether or not you become addicted.

“Genes are not probably behind the first cigarette you pick up when you’re 13 or 14, which is usually influenced by your peers,” said Tyndale, also a researcher at the Centre for Addiction and Mental Health. “But once you’ve started to have cigarettes, then that component of genetics is quite strong.”

Manoli, now 25, had thought about smoking before she started that winter day.

“I had taken a cigarette from my mother’s pack before and held it and thought about it,” she said. “Just holding the cigarette felt like a huge betrayal.”

The Toronto native has always been surrounded by smoke. Both of her parents and her sister smoke. All started in their teens.

By smoking she was defying hopes that she wouldn’t follow her smoking destiny.

Even her grandmother, who started in her 40s, smokes.

“It’s kind of all my grandmother and I do together. We sit and chat; that usually involves smoking,” Manoli said.

This kind of legacy of family smoking is one element researchers like Tyndale look for when they are determining the influence of genes on a smoker’s addiction.

Tyndale works with Dr. Peter Selby, director of addiction programs at CAMH, to understand the way genetic factors determine how quickly nicotine — the addictive element in cigarettes — is metabolized by the liver.

“If you’re very fast at it, you tend to inhale more deeply and smoke more cigarettes. If you’re very slow, you tend to smoke fewer cigarettes and inhale less deeply,” Tyndale said.

Genes can influence a person’s addiction to cigarettes in two ways: Some people have a greater number of nicotine receptors in their brain, causing them to have deeper cravings for the buzz of nicotine; or their genes can determine how quickly they break down nicotine through the production of an enzyme in your liver.

Selby, a doctor trained in psychiatry and family medicine, tries to take genetics into account when counselling patients.

“Many multiple genes, when taken together, account for about 60 per cent of why people start smoking and why they have difficulty stopping,” he said.

His work has revealed that our genes can determine whether people enjoy the taste of smoking, how quickly someone can become addicted or whether someone becomes addicted at all.