Cig addiction could be in your genes

08 March 2009


Tobacco causes around a quarter of all cancer deaths in the UK, as well as heart disease, lung disease and other heart problems.  And it's a fiercely addictive drug, meaning that people find it hard to give up. But some people do manage to quit the cigs relatively easily, while other fight a life-long battle.  And what makes some people become addicted after just a few puffs, while others can smoke a few cigarettes then just stop.

A cigaretteNow researchers from across the US have used the latest DNA analysis techniques to hunt for genes linked to smoking behaviour, with the hope of shedding light on this conundrum.

The team looked at DNA from over 2,300 men and more than 2,200 women - a mixture of smokers and non-smokers - and looked at their smoking behaviour. This included the number of cigarettes smoked per day, age they started smoking, how long they had smoked for, and pack years (for example, one pack year is the equivalent of smoking one pack  day for a year, or half a pack a day for two year). The scientists also looked at whether the people had ever smoked, or if they had managed to give up.

The researchers used so-called SNP ("snip") analysis to track down potential genes linked to specific smoking behaviours. In total, around 2,600 of the people in the study had ever smoked. Although they didn't find any new genes linked to smoking, the results provided more evidence to support the existence of an important gene on chromosome 15 linked to the number of cigarettes smoked per day.

The team also found evidence for variations in genes encoding nicotine receptors being involved in some smoking behaviours, as might be expected, including the number of cigs smoked per day, the number of pack years, and the age they started smoking. And they also found a link between variations in a gene region called MAOA on the X chromosome and whether people smoked more or less than 10 cigarettes per day.

This is an intriguing gene, as some studies have shown possible links with alcoholism and Parkinson's disease, so it needs more investigation.  And another interesting result was a link between variations at alcohol dehydrogenase genes and whether a person had ever smoked, or never smoked.  So perhaps these genes are linked to whether a person actually ever starts smoking.

But the main thing the team took from their study was that the links between any of these genes and specific smoking behaviours, although it has thrown up some interesting candidates that merit further research. But the true picture is likely to be very complex, involving social as well as genetic factors.


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