There is growing evidence that the risk factors for addiction change throughout one's lifespan.
The risk factors for developing addiction in adolescence are the most intensively studied because this life phase is associated with the highest addiction risk. Traits linked to addiction risk during adolescence include pleasure-seeking, behavioural disinhibition, and devaluation of future negative consequences of behaviour. In contrast, the development of substance use among adults is more commonly associated with high levels of stress, anxiety, and depression.
Thus, perhaps it is not surprising that different sets of genes are now implicated in the risk for addiction in adolescence and adulthood.
In a new study published in Biological Psychiatry, researchers 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.
"These findings seem to make some sense. The dopamine-related genes may be more closely associated with the risk for addiction within the context of thrill-seeking, while cholinergic receptors, which have been implicated in mood and cognition as well as addiction, might contribute to self-medication models of addiction," commented Dr John Krystal, Editor of Biological Psychiatry.
The researchers say 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. However, further research is necessary before these goals could be implemented. - (EurekAlert!, April 2011)