Although environment plays a major part in addiction — you can’t get hooked on something you’ve never tried — genetics plays a substantial role in determining whether a person who does use a drug will become addicted to it.

A few DNA variations have been identified that seem to increase the odds a person will become addicted to a specific drug. But twin studies suggest that there might be genes influencing addiction in general.

Xiang Chen and colleagues at Yale and Princeton set out to find some of these genes by analyzing the genetic data from several cohorts of people previously studied for addictions.  The researchers’ approach was to look for variations found more frequently in people addicted to at least two out of six categories of substances: nicotine, alcohol, marijuana, cocaine, opiates and other drugs.  Their results, published online this week in the Proceedings of the National Academy of Sciences, reveal a significant association between addiction and variations in a gene, PKNOX2, previously associated with alcohol dependence in mice.

The strongest signal was seen with rs12284594.  In white women, each copy of a G at this SNP corresponded to 1.77 times increased odds of being addicted to two or more substances.  The association with addiction of this and other SNPs in the PKNOX2 gene was also seen in the white men and black men and women in the study, but the findings were not statistically significant.

(23andMe customers can check their data for rs12284594 using the Browse Raw Data feature.)

The association of rs12284594 with addiction did not hold when the researchers looked at individual substances separately.

“This suggests that substance dependence or addiction as a whole has different risk genes compared to any single addiction outcome,” the authors write.

The authors admit that there are weaknesses in their study.  For example, people addicted to two or more substances might just have more access to drugs — not a biological predisposition to addiction.  Moe research in this area will definitely be needed.

SNPwatch gives you the latest news about research linking various traits and conditions to individual genetic variations. These studies are exciting because they offer a glimpse into how genetics may affect our bodies and health; but in most cases, more work is needed before this research can provide information of value to individuals. For that reason it is important to remember that like all information we provide, the studies we describe in SNPwatch are for research and educational purposes only. SNPwatch is not intended to be a substitute for professional medical advice; you should always seek the advice of your physician or other appropriate healthcare professional with any questions you may have regarding diagnosis, cure, treatment or prevention of any disease or other medical condition.

More Spittoon Posts About Addiction and Substance Dependence:
SNPwatch: Genetic Variation May Make It Harder For Expectant Moms To Quit Smoking
How A Person Smokes Might Affect Lung Cancer Risk
SNPwatch: Two Vices, One SNP — Drinking and Smoking Behavior Both Linked to Nicotine Receptor Genes
SNPwatch: Focusing on a Gene Variant that Might Help Counter Cigarette Cravings
SNPwatch: “Environment” also genetic?
SNPwatch: Genetic Variant Linked to Drinking Intensity in Alcoholics
SNPwatch: Next Year It’s Martinelli’s…
SNPwatch: Unlikely Gene May Contribute To Cocaine Dependence and Paranoia

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