Can genetics help you stop smoking?

Researchers have linked a gene with your ability to stop smoking, but not all of the scientific community is in agreement. 

If you're struggling to give up smoking, you might be wondering why some people find it easier than others? This week Dr Yunlong Ma and colleagues, from Zhejiang University School of Medicine, published findings in Translational Psychiatry identifying a gene called DRD2 that may influence your ability to quit. Could genetics be to blame?

The team of researchers selected DRD2 for study based on what is already known about its biology.

DRD2 encodes a receptor that receives chemical signals in the brain. This receptor responds to dopamine, a chemical involved in pleasure and frequently linked with addictive behaviours. This link to addictions makes DRD2 an obvious candidate for study in relation to smoking.

The scientists were trying to establish whether different versions of the gene are associated with a greater success of giving up smoking.

In order to do this they gathered information from a number of previous studies and brought data from more than 11,000 subjects together for analysis.

This makes the analysis more powerful than each of the previous studies, but still has limitations. The results "should be interpreted with caution, " the authors acknowledge in their paper.

The previous studies were small and often had questionable results. Some of the studies also included other factors, such as medication, which might influence findings. Commenting on the paper, Bristol University's Marcus Munafo, who wasn't involved in the study, explained "for the most part, the findings proved very difficult to replicate and reproduce."

In 2010, using an approach known as genome wide association, the Tobacco and Genetics Consortium published a paper in Nature Genetics and identified several regions of the genome linked with stopping smoking. Using this approach, researchers can "look across the whole of the human genome and simultaneously test hundreds of thousands of genetic variants," says Munafo. This is useful because it identifies genetic regions that researchers may, as yet, know little about.

That study used data from over 70,000 people and didn't find an association between the DRD2 gene and giving up smoking.

It is possible that the two different approaches will agree at some point in the future. As larger and larger Genome Wide Association studies are carried out more genes will be identified but "at the moment it's an inconsistency we have to be aware of," cautions Munafo.

One of the reasons it is difficult to match up the two approaches is that the influence of individual genes is very tiny and difficult to detect. Collectively, your genetics play a significant role in determining some behaviours but individual genes have minimal impact.

If you were hoping for a personalised treatment based on your genes to help you kick the habit, I'm afraid you might be disappointed. It is unlikely that genetic information will be useful for smokers trying to quit in the foreseeable future. "Things like how heavily you smoke are a much stronger predictor of how hard you're going to find it to stop smoking."

Professor Munafo does have some reassurance if stopping smoking is going to be your New Year's resolution. "Most people only stop smoking after a series of attempts so being persistent is the most successful way to stop smoking..."