The lead author, Joel Gelernter, M.D., professor in the Department of Psychiatry, said the researchers recruited a sample of 393 small families, most with at least two individuals with opioid dependence. They then searched genetic signposts throughout the entire genome in an effort to identify markers that, within the same family, would show that individuals who share the illness also share marker alleles, or gene variants.
This information allowed the team to identify where genes influencing opioid dependence are located. Gelernter said the researchers found evidence of gene linkage for opioid dependence. They also found strong evidence of linkage in the family groups for the symptom cluster traits characterized by dependence on substances other than opioids, specifically, alcohol, cocaine and tobacco.
"These results provide a first basis to identify genes for opioid dependence from a genome-wide investigation," Gelernter said. "Research in the laboratory now is focused on finding specific genes that modify risk for opioid dependence."
He said that although environment plays a significant role, it is well established that substance dependence risk is also genetically influenced. Understanding the genetic factors that influence opioid dependence risk would represent major progress toward understanding the basic biology of the disorder.
"Once specific genes that increase or decrease risk are known, we will be in a better position to figure out exactly what the environmental factors might be and, perhaps, how they can be modified to protect people who are genetically at risk," Gelernter said.
The study was a collaborative effort involving investigators at Yale, the University of Connecticut Health Center, McLean Hospital in Boston, the Medical University of South Carolina, and Boston University. The National Institute on Drug Abuse supported the study.
The American Journal of Human Genetics: (Published online March 16, 2006. DOI 10.1086/503631)