Researchers estimate that half of a person's propensity to become addicted to cigarettes is genetically determined. However, the hunt for the involved genes is in its infancy, says Ming Li, PhD, a University of Virginia psychiatrist.
Li recently published a paper in Human Genetics (Vol. 123, No. 2) reviewing current efforts to identify these smoking "risk genes." After sifting through the research, he identified four areas on four different chromosomes that probably play a role in smoking addiction, as well as eight regions that also deserve further research. However, identifying the regions is just the first step in the process. Next, they must sift through the 500 to 1,500 genes in each region and figure out what they do.
Tracing the action of genes on the brain and body will be no easy feat, notes Steven Grant, PhD, from the National Institute on Drug Abuse. It's entirely possible, even likely, that the genes responsible for smoking's reward system activation are completely different from the ones that trigger dependence, Grant says.
"Don't think that smoking addiction is a simple, single phenotype," says Li. "It's a complex disorder."