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Genetics and teen smoking risk

6 January 2011 

Researchers have uncovered two genetic variants that make teenagers more likely to become heavy smokers.

Teenagers carrying variants in two gene regions were shown to be three times more likely to become regular smokers in adolescence and twice as likely to be persistent smokers in adulthood, compared to non-carriers. One variant is associated with a person's risk of starting smoking while the other influences their chances of carrying on with the habit into adulthood.

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.

Most smokers start the habit as teenagers, yet adolescent smokers are poorly studied compared to adults.

The study was conducted by scientists at the Institute of Psychiatry, King’s College London and the School of Public Health, Imperial College, both in London, UK, and the University of Oulu, Finland.

“Research looking at the genetics behind smoking behaviour in adolescents is rare, which is surprising as most people who start smoking do so at that time in their life," says Dr Francesca Ducci, a clinical lecturer at IoP and lead author on the study.

The researchers studied data from 5,000 Finnish people tracked from birth until mid-adulthood.

Looking at smoking habits and participants' genetic data, they found two chromosome regions that influenced two different types of smoking behaviour. The 11q23 region of chromosome 11 was associated with a person's risk of starting smoking while the 15q25 region of chromosome 15 influenced their chances of carrying on with the habit into adulthood. These regions include genes encoding for receptors of two chemicals involved in nicotine’s effect on the brain: dopamine and acetylcholine.

The variant on chromosome 11 had a stronger impact on smoking initiation in adolescents than in adults – individuals carrying it had a 1.3-fold increased risk of starting smoking in their teenage years.

In contrast, they found that the variant on chromosome 15 had a stronger influence on making adults heavy and persistent smokers than on adolescents. Those carrying this variant had a 1.3-fold increased risk of becoming a heavy and persistent smoker in adulthood.

“New treatments could target these genes and weaken the effect that nicotine has on them, reducing a smoker’s chances of sticking with the habit” said Gunter Schumann, Professor of Addiction Biology at the IoP.

Environmental factors such as those relating to family and social disadvantage are also strong independent predictors of smoking, both in adolescence and adulthood. However, the findings improve our understanding of the biological mechanisms causing people to start smoking and to develop a heavy pattern of use.

The paper is published in the US journal, Biological Psychiatry, to read, ‘TTC12-ANKK1-DRD2 and CHRNA5-CHRNA3-CHRNB4 Influence Different Pathways Leading to Smoking Behaviour from Adolescence to Mid-Adulthood’ please follow the link.

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