You have a gene. It’s called “cholinergic receptor nicotinic alpha 5 subunit,” or CHRNA5 for short. It does important things inside your body. Certain sections of it, for example, dictate how your brain processes nicotine. That’s true for everybody. You may, however, have variants in and near this gene that put you at risk: They make you more likely to become a heavy smoker; to develop lung cancer and develop it earlier; and to struggle more than other people to quit. This is all backed up by solid published scientific research. Most of it has circulated for a decade or more.