Genes for addiction

Scientists have found a further gene for insurance companies to quiz us about - this one linked to addiction.

Writing in PNAS Yale Medical School researcher Heping Zhang and his colleagues made the discovery by screening the genomes of more than 4000 people included in the Study of Addiction: Genetics and Environment (SAGE) database.

The team were looking for genetic markers called SNPs - single nucleotide polymorphisms - which can be used to flag up certain gene sequences shared by groups of individuals. The SNP profiles from study subjects who had a history of addiction, including addiction to alcohol, nicotine and other substances, revealed a hotspot on chromosome 11, which the team were able to track down to a gene called PKNOX2. No one knows exactly what this gene does, but it appears to regulate the activity of other genes and it has been linked to alcohol addiction in mice previously. But most importantly the finding provides an interesting lesson - because the gene seems to be linked to substance addiction in general, rather than any one specific substance; in other words, when the researchers looked just at nicotine or cocaine addiction the effect of PKNOX2 was not statistically significant.

This shows that it probably plays a role more as a general behavioural risk factor rather than in promoting any one addiction per-se. Also, the effect was most marked only in women who were of European origin, indicating that the gene almost certainly has some other partners in crime that have yet to be uncovered. But above all, this study is important because it shows that nature as well as nurture plays a role in substance abuse and addictive behaviour.