'Addiction gene' puts white women at high risk of drink or drug abuse

Published on Monday 31 August 2009 21:35

AN "ADDICTION gene" has been identified that makes white women more likely to become dependent on drink or drugs.

The breakthrough opens up the possibility of a DNA test to screen for those people who are most at risk of becoming drug addicts or alcoholics.

A study of 3,627 volunteers found women of European origin with a mutated version of a gene, known as PKNOX2, were almost twice as likely to become substance abusers than those without the variant.

However, no such link was found among black people or men, according to the findings published in the journal Proceedings of the National Academy of Sciences.

The researchers defined addiction as being dependent on at least six substances including nicotine, alcohol, marijuana, cocaine, opiates or other drugs. Although previous studies have found genes associated with specific addictions, such as alcohol and nicotine, none has reported a specific "addiction gene".

Epidemiologist Dr Xiang Chen, of Yale University, said: "We have found a genome-wide significant association of a composite substance dependence with a mutation in the PKNOX2 gene in white women."

The gene was linked with alcohol addiction in mice in research published several years ago, but has not been reported before as being associated with substances dependence in humans.

Dr Chen said: "Our findings make an important contribution in reporting PKNOX2 as a candidate gene for substance dependence, particularly for white women in the sample."

Dr Chen said it was not surprising the same association had not been identified in all four sub-samples of the study group – 1,393 white women, 1,131 white men, 568 black women and 535 black men.

He said: "Different ethnic groups have vastly different underlying genetics for many complex diseases, and these differences may confound association results when they are pooled together as one in the analysis. Previously, racial differences in the prevalence of substance abuse have been reported."

The researchers said substance abuse is "a complex disorder" influenced by both a person's environment and genetics.

Although there is merit to examining individual addictions, the finding underscores the importance of studying substance abuse as "an integrated entity".

Dr Chen added: "There is strong evidence that vulnerability to substance dependence or addiction … is a complex trait with both genetic and environmental components.

"Whether legal or illicit, an answer to substance abuse is one of the most sought-after phenomena in many populations because of its serious health and socioeconomic consequences."