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Addiction May Be in the Genes

December 04, 2000|ERNEST P. NOBLE | Ernest P. Noble is a professor of psychiatry and director of the Alcohol Research Center at UCLA's Neuropsychiatric Institute and Hospital

Why would a talented and successful actor like Robert Downey Jr. repeatedly risk his career for the sake of a drug-induced high?

For many addicts like Downey, the answer may lie not in their upbringing or the company they keep, but in their genetic makeup.

And for drug users whose DNA plays a role in their habit, clinicians need to turn their attention to new treatment options that address the genetics of addiction.

Downey's very public yet personal struggle is a familiar story to millions of Americans who struggle with addiction. A quarter of the U.S. adult population is hooked on alcohol, cocaine, nicotine, amphetamines or some other substance.

Through most of the 20th century, we viewed addiction largely as the product of a flawed upbringing or bad character. Addicts deserved punishment, not sympathy.

Studies comparing the lifestyles and habits of twins and adopted children first suggested that addictive behavior has a hereditary component. We began to consider the possibility that we might find the root cause of addiction in our genetic makeup. A major breakthrough in understanding the genetics of addiction came in 1990, when researchers first linked a gene called DRD2--later nicknamed the "pleasure-seeking" gene--to severe alcoholism.

UCLA studies of brain tissue showed that individuals with the "A1 variation" of the DRD2 gene have significantly fewer dopamine receptors in pleasure centers of the brain.

The findings suggest that many addicts use drugs, which increase brain dopamine levels, to compensate for the deficiency in their neurological pleasure system.

Subsequent studies linked the A1 variation of the DRD2 gene to cocaine, amphetamine, heroin and nicotine addiction.

What does this all mean? It means simply that people with this genetic trait are much more susceptible to addiction. In addition, they are more likely to fall prey to the most severe forms of addiction. In fact, data show that while only 10% of the general population in the United States has the A1 variation of the DRD2 gene, it is found in about half of addicts.

Meanwhile, the implications for treatment programs are becoming increasingly clear. A UCLA study of heroin addicts published this past summer showed that a high percentage of heroin users who respond poorly to traditional addiction treatment programs have the troublesome A1 variation of the DRD2 gene.

And a recent study of alcoholics showed that patients with the same "pleasure-seeking" trait responded well to treatment with a nonaddictive drug that stimulates the dopamine receptors.

These findings demand that clinicians rethink treatment options for the millions of drug-users who are genetically predisposed to addiction.

The implications carry additional weight in California, where voter-approved Proposition 36 will divert tens of thousands of addicts a year from the criminal justice system into treatment.

A simple cheek cell test of DNA can help differentiate hard-core, genetic addicts from those who developed bad habits while socializing with bad crowds.

Drug abusers with a genetic propensity toward addiction typically require one of a growing number of innovative prescription drug therapies to beat their habit. Those without the gene more often respond best to counseling that addresses environmental factors that led to their drug abuse.

The more we know about why the body craves drugs and the more we put that knowledge to use, the more successful we will be in mitigating the heavy toll that drug addiction takes on individuals, families and our society.

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