Scientists have found that different sets of genes are implicated in the risk for smoking addiction in adolescence and adulthood.
They found that teenagers carrying variants in two gene regions were three times more likely to become regular smokers in adolescence and twice as likely to be persistent smokers in adulthood, compared to non-carriers.
Variation in a set of dopamine-related genes was associated with a person's risk of starting smoking, and these genes had a stronger impact on smoking initiation in adolescents than in adults.
Individuals carrying the risk variants had a 1.3-fold increased risk of starting smoking in their teenage years.
The other set of genes coded for subunits of the nicotinic cholinergic receptors, the brain targets for nicotine inhaled during smoking.
Variation in these genes influenced the likelihood of smokers continuing the habit into adulthood, as it had a stronger influence on the smoking habits of adults than of adolescents.
Those carrying these variants had a 1.3-fold increased risk of becoming a heavy and persistent smoker in adulthood.
The researchers said the findings could help develop genetic testing for those wishing to know their susceptibility to nicotine dependence and tobacco-related disease.
It could also pave the way for targeted drugs that influence an individual's response to nicotine.
The findings appear in the April 1 issue of Biological Psychiatry.