The tachykinin receptor 3 gene has been linked to alcohol and cocaine dependence

This study is part of the larger Collaborative Study on the Genetics of Alcoholism (COGA), said Foroud, which had previously detected a link between AD and a region on chromosome 4q. “We believe it is likely that multiple genes contributing to AD lie within this chromosomal region,” she said. “Given that several lines of evidence suggested that TACR3 was a good candidate gene, we decided to not only test for an association with AD, but also expand our analyses to include additional phenotypes, such as cocaine dependence.”

Using COGA data, researchers searched for an association between AD and 30 SNPs throughout TACR3 among 219 European American families (n=1,923 genotyped individuals). Researchers also looked for any association with cocaine dependence.

“We have identified a gene that we believe contributes to the risk for AD,” said Foroud, “and is, furthermore, particularly important for those individuals who meet not only the DSM-IV criteria for AD but also the more stringent ICD-10 criteria. Furthermore, we found that this gene was also strongly associated with cocaine dependence.”

Foroud said these results help support the theory that there are many genes, each with small individual effects, that contribute to the risk for AD. “Furthermore, this study highlights the importance of studying multiple phenotypes – such as alcohol and cocaine dependence – to try to understand how a gene might contribute to multiple disease risk.” She and her colleagues plan to continue analyzing TACR3 in the COGA sample.

Dick is optimistic about the potential returns on future genetic research. “While any one gene on its own just has a very small effect in altering risk,” she said, “once we catalog many of the genes involved in the development of dependence, this could lead to better individual-risk assessment, which may lead to improved prevention and intervention programs.”

Alcoholism: Clinical & Experimental Research (ACER) is the official journal of the Research Society on Alcoholism and the International Society for Biomedical Research on Alcoholism. Co-authors of the ACER paper, “The Tachykinin Receptor 3 (TACR3) is Associated with Alcohol and Cocaine Dependence,” were: Leah Flury Wetherill, John I. Nurnberger, Jr., Xiaoling Xuei and Howard J. Edenberg of the Indiana University School of Medicine; John Kramer of the University of Iowa Carver College of Medicine in Iowa City; Jay A. Tischfield of the Human Genetics Institute at Rutgers University; and Marc A. Schuckit of the University of California, San Diego. The study was funded by the National Institute on Alcohol Abuse and Alcoholism, and the National Institute on Drug Abuse.