STUDY: VULNERABILITY TO DRUG ADDICTION IS ROOTED IN GENES

CHICAGO - Drug addiction has become a pervasive and pernicious
problem, not simply because of the wide availability of drugs, but
also because nearly everyone inherits a vulnerability for addiction to
mind-altering chemicals, according to new research.

Just as certain genes make some people more prone to heart disease,
cancer or Alzheimer's disease, scientists now believe that other genes
may make them more susceptible to becoming addicted to heroin,
marijuana or other compounds that affect the brain's natural reward
system.

"It appears that the genetic vulnerability for substance and alcohol
abuse is fairly general in our society," said Dr. David Goldman, chief
of neurogenetics at the National Institute on Alcohol Abuse and Alcoholism.

Full Text:

CHICAGO - Drug addiction has become a pervasive and pernicious
problem, not simply because of the wide availability of drugs, but
also because nearly everyone inherits a vulnerability for addiction to
mind-altering chemicals, according to new research.

Just as certain genes make some people more prone to heart disease,
cancer or Alzheimer's disease, scientists now believe that other genes
may make them more susceptible to becoming addicted to heroin,
marijuana or other compounds that affect the brain's natural reward
system.

"It appears that the genetic vulnerability for substance and alcohol
abuse is fairly general in our society," said Dr. David Goldman, chief
of neurogenetics at the National Institute on Alcohol Abuse and Alcoholism.

"It's probably not wise for anyone to think that they're not
vulnerable to some substance of abuse," he said. "If you tested an
entire population and identified everybody who's vulnerable to drug
abuse, you could probably put everybody's name on the list."

In underscoring the roles that genes and environment play in causing
addiction, the new findings open the possibility of developing the
first effective prevention and treatment strategies for drug abuse.

Long-held beliefs debunked

The findings reveal the inherited biology that turns some people into
mean drunks and debunk long-held beliefs, such as the notion that
marijuana use puts an individual on the path to cocaine or heroin use.

Western cultures tend to view addiction as a sin to be condemned or as
a disease to be treated, Goldman said.

"The fact that we have failed too often with either approach suggests
that a better understanding of the origins of addiction could be
useful to help people make better decisions and to improve the basis
of intervention," he said.

A study of identical and fraternal twins found that, in general,
genetic influences account for one-third of addiction, family another
third and peers, friends and co-workers the remaining third.

Between 60 million and 70 million Americans have tried an illegal drug
sometime in their life, and 4.2 million have become addicted.
Sixty-five million Americans drink alcohol, and slightly more than 8
million have become dependent. Thirteen percent of Americans 12 and
older are heavy cigarette smokers, more than a pack a day, and 57
percent of them say they find it difficult to quit.

Not all addictions equal

But not all types of addiction are equal when it comes to the impact
of genes. The study, which appears in the Archives of General
Psychiatry, found that genes accounted for more than half of the risk
of heroin addiction but only 26 percent of the addiction to
psychedelics. The biggest factor influencing addiction to psychedelics
is the nonfamily environment, including friends, schoolmates and
co-workers, which accounts for 53 percent.

For marijuana addiction, the nonfamily environment also has the
biggest influence, accounting for 38 percent and with genes at 33 percent.

"Some of these addictions - for example, alcohol and opioid abuse -
are more heritable than susceptibility to coronary artery disease or
obesity," Goldman said.

"While there's a clear environmental component, it nevertheless works
out that for somebody living in modern society, a prediction as to
whether they would have a problem with alcohol or another substance
would be substantially dependent on their genetic background," he said.

Although addiction-predisposing genes are not yet known, finding them
has become a major goal of the National Institute on Drug Abuse. Early
success by researchers in linking some genes to alcoholism has
persuaded the drug abuse institute to do the same thing for the genes
of addiction.

"With the emergence of new genetic technologies and ways to actually
look inside the human genome, we decided the time is right to mount a
major initiative to try to understand the role of genetic influences
on the vulnerability to addiction," said Dr. Alan Leshner, director of
the drug-abuse institute.

The ability to diagnose genes that make a person more susceptible to
specific addictions could result in the development of medicines that
block a drug's action.

The study, headed by Harvard's Dr. Ming Tsuang, also overturns the old
belief that the use of less-addictive drugs such as marijuana sets
people on the path to becoming hooked on cocaine or heroin, the
so-called "marijuana gateway."

Although some people abuse every drug they can, because these drugs
affect a major chemical path in their reward system, others have genes
that make them addicted to one type of drug that affects only a very
specific part of the reward mechanism.

"There are genetic effects that make some people predisposed to
substance abuse," said Dr. Jack Goldberg of the University of Illinois
at Chicago School of Public Health.

"It doesn't mean that addiction is predetermined by genes. It just
means that some of us are more susceptible than others to abusing
drugs if we try them," said Goldberg, who participated in the study.

The study involved 3,372 male twin pairs from the Vietnam Era Twin
Registry. The registry was established to study the effects of Agent
Orange exposure on soldiers in Vietnam. It has since been used to
examine the roles that genes and environment play in sleep disorders,
post-traumatic stress disorder, alcoholism and other problems.

Twins are used to evaluate the relative influences of genes and
environment since identical twins share 100 percent of their genes and
fraternal twins share 50 percent.