Nicotine dependence / cigarettes per day

The CHRNA5 gene builds part of a nicotine receptor in the brain. A common variant in it changes how that receptor responds to nicotine and is one of the strongest common signals for heavier smoking, stronger dependence and harder quitting, but only in people who smoke.

Possible results

Typical nicotine response. You carry the common version of CHRNA5, the gene for part of a brain nicotine receptor. If you smoke, your dependence and how many cigarettes you tend toward are in the usual range for this gene. If you never smoke, this variant has no effect on you.

Higher dependence if you smoke. You carry one copy of the CHRNA5 variant that changes how your brain's nicotine receptors respond, which is linked to somewhat stronger nicotine dependence and smoking a bit more if you smoke. It says nothing about whether you'll start, and it has no effect if you never smoke; for smokers it can mean quitting is harder, so extra support or nicotine-replacement help is worth considering.

Strong dependence if you smoke. You have two copies of the CHRNA5 variant most tied to heavier smoking, stronger nicotine dependence and a higher risk of smoking-related lung disease among people who smoke. This only matters if you smoke: it doesn't cause never-smokers any harm and doesn't make anyone start. If you do smoke, quitting is likely to feel harder, so structured support, medication or nicotine replacement can make a real difference.

Evidence & sources

Across global populations, about 10% of people carry two copies of this variant, and about 50% carry none.

This variant appears in 4 published genetic studies: PubMed 29758381 · PubMed 30679032 · PubMed 31294817 · PubMed 40157913.

Related

BDNF memory & stress variant (Val66Met) · Coffee consumption · COMT "warrior vs worrier" (stress & dopamine) · Dopamine reward sensitivity (DRD2 Taq1A) · Morning vs evening preference (CLOCK) · Oxytocin receptor / empathy tendency