Yale Bulletin and Calendar

April 6, 2001

Volume 29, Number 25

Scientists get $9 million from NIDA
to study genetics of addiction

Siblings who are addicted to cocaine and opioids, among them morphine, codeine and heroin, are being recruited for studies by Yale researchers to determine the locations of genes that increase risk for these addictions, as well as for tobacco addiction.

The study of the genetic links of cocaine and tobacco dependence is funded with a $6 million grant from the National Institute on Drug Abuse (NIDA), which also is funding a $3 million project led by a Yale researcher looking at the genetics of opioid dependence.

"It turns out that the heritability of cocaine dependence, which is the magnitude of the genetic contribution, is quite high -- higher than anyone would have expected," says Dr. Joel Gelernter, associate professor of psychiatry at Yale and principal investigator of the two projects. "It is something in the range of 60% to 70% or even higher. That means that of all of the things that go into determining if you'll be cocaine dependent or not, about 65% or 70% were in your genes before you were born, and the environment is everything else."

"The heritability for cocaine dependence is even higher than for alcohol dependence, which is about 55%," he adds. "The fact that the genetic contribution is so high means that the odds of us finding something in terms of specific genes are very good."

The heritability figures are based on previous studies of twins and cocaine dependence. Identical twins share 100% DNA, and fraternal twins, like any other siblings, share 50% of their DNA. Gelernter says that although identical and fraternal twins are raised in the same environment, cocaine dependence is much more likely to be diagnosed in both members of an identical twin pair than in both members of a fraternal twin pair.

The goal for the Yale cocaine study is to recruit 500 families with affected sibling pairs and then to type genetic markers that show regions of the genome that, based on statistics, are likely to contain genes that influence risk for cocaine dependence. "Then we hope to go from there to actually identifying what the genes are," Gelernter said. An additional 250 families will be recruited for the opioid genetics study.

In addition to Yale, patients are being recruited for the study by McLean Hospital in Boston (Harvard University), Medical University of South Carolina and the University of Connecticut.

Gelernter says once researchers identify the genes involved in these addictions, it will help them understand the physiology, thus paving the way for further investigation, understanding, treatment, prediction of risk and primary prevention.

"The fantasy would be that we could do a simple DNA test of someone who we thought was at risk early on, and then do some type of modification of the environment that might be protective," he says. "Or we could put the person on some type of medication before he or she was ever exposed to cocaine to modify what the risk would be."

-- By Jacqueline Weaver

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