Genetic test tells which smokers become addicted

Scientists have discovered that genes determine how many cigarettes people smoke each day, and who will become addicted.

Scientists have discovered that genes determine how many cigarettes people smoke each day, and who will become addicted.

A new genetic test for tobacco addiction based on the work by the British researchers could now revolutionise the success rate for anti-smoking therapies. Those who want to give up would be able to choose a treatment that would work for them. Instead of trying different drugs, patches and other therapies, doctors could use a smoker's DNA to match him or her with the treatment likely to be most successful.

Results of research involving more than 800 smokers are to be published shortly and will show the test was able to predict accurately which of them would give up the habit when they used a nicotine patch.

The test has been developed by researchers at Oxford University who have found a link between the way the body metabolises dopamine (a neurotransmitter) and nicotine and the likelihood of an individual being a smoker. "It seems that people whose genes determine they are slow metabolisers are likely to be protected from addiction to smoking," says Dr Robert Walton, a lecturer at the university and a member of the research team. "If the effects of nicotine are metabolised slowly and last for 12 hours or so, there is not going to be the craving for another cigarette.

"We have shown that genetic variation in enzymes which metabolise dopamine in the brain are important in determining the amount of tobacco that smokers consume. It is the first study to demonstrate this link."

The team has found that people with different genetic mutations of the enzymes smoke a different number of cigarettes a day. It has also found different genetic mechanisms at work in men and women smokers. The researchers believe heavy smokers have genetic variations that reduce natural dopamine activity. The individual is addicted to smoking heavily because nicotine from the cigarettes restores the brain's dopamine levels to normal.

The team reckons about 20 genes may be involved in the smoking process, half dealing with the nicotine metabolisation, the other with dopamine. "Our new data will show we can predict whether people will stop smoking using a nicotine patch," says Dr Walton. "The patch is the best way to give up smoking but the success rate is only 20 per cent.

"The test is designed to predict which people will benefit from the different therapies. People who metabolise nicotine quickly may respond best to a nicotine patch. Those who met-abolise nicotine very rapidly may need a higher replacement dose than slow metabolisers." Others may respond better to dopamine therapyinvolving buproprion, or to behaviour therapy. "Using genotyping to target the most appropriate treatment for the smoker could lead to more effective treatment for tobacco addiction."