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Is alcoholism genetic?

-A curious adult from California

April 14, 2006

Alcoholism definitely seems to run in families. For example, kids who have alcoholic parents are four times more likely to end up alcoholics than are other children.

Sounds like genes are involved, right? Not necessarily.

It isn't surprising that kids living with alcoholics are more likely to end up alcoholics themselves. It just makes sense.

So how do you separate genes from the environment? Are these kids' genes responsible? Or are they just learning to be alcoholics by watching their parents?

Both are probably true. Scientists are able to figure out how much each of these factors contributes to a trait by studying twins. Remember, there are two different kinds of twins -- fraternal and identical.

Identical twins have exactly the same genes. Fraternal twins share only as many genes as do any brother or sister.

If something happens more often to both twins in an identical pair, then genes are involved. If it happens at about the same rate to both twins in fraternal and identical twins, then the environment is most important.

Twins in an identical pair are more likely to both be alcoholics as compared to fraternal twins. This tells us that there are probably genes involved. But they aren't the whole story -- the environment plays a role too.

We know this because both twins in an identical pair are not always alcoholics. Sometimes only one twin is an alcoholic. If just genes were involved, then both twins in an identical pair would always be alcoholics since they have the exact same genes.

OK, so genes and the environment both play a role. What this most likely means is that there are some genes that make someone more likely to be an alcoholic. In other words, our genes are not destiny (at least not for alcoholism).

How could a gene make someone more likely to become an alcoholic? By affecting how likely it is for someone to take up drinking, how much alcohol it takes to get drunk, how much pleasure we get from alcohol, etc. Being an alcoholic is such a complex behavior that lots of genes are involved.

For example, an alcoholic gets a lot of pleasure from alcohol. More than the average person. Scientists have found that people who are more likely to end up alcoholics have specific changes in these genes. Presumably, these changes somehow make alcohol more pleasurable.

There are changes in genes that affect the amount of alcohol it takes to get drunk. One gene change makes alcohol taste less bitter. Another makes it so alcohol breaks down faster. The more alcohol you drink, the more likely you are to end up an alcoholic. So having these DNA changes predisposes you to being an alcoholic.

There are probably genes related to risky behavior like those that have been proposed for smoking. They've even identified some DNA regions that might be responsible for people who like to drink and smoke at the same time!

As you can see, there are lots of changes in genes that can make someone more likely to be an alcoholic. And these changes can be passed down to children.

Why do we care? Because knowing whether someone has these DNA changes may make it possible for them to know if they are at risk. Remember, having certain versions of these genes doesn't mean you'll end up an alcoholic. It only means you are more likely to become one.

And if we can identify these people early, we can steer them away from alcohol. Or at least let them know the risks involved so they can make their own decision.


Alcoholism runs
in families


Some DNA changes make
alcohol more pleasurable