To keep people from getting into trouble with alcohol, it would help to know why they're at risk.

Genes make some people more susceptible to dependence or addiction, while the surroundings exert a stronger pull on others. But it's been devilishly hard for researchers to sort those out. Context — who's drinking where and when with whom — matters a lot.

Add in money and it gets even trickier. And we're not talking about whether you can afford microbrews.

A person's income level influences the push and pull of genes and the environment, according to a study published Tuesday in the journal Alcoholism: Clinical and Experimental Review.

There was a lot more variation in how much people drank if they had lower incomes, with some drinking heavily and others drinking not at all, the researchers found. By contrast, people with higher incomes were more likely to drink, but also more apt to moderate their drinking.

One in 3 American adults drink too much, according to the Centers for Disease Control and Prevention.

Genetics had a bigger influence on drinking habits in low-income people, with environmental influences playing more of a role with higher-income people. It may be that family norms about drinking are more uniform in higher-income communities, the researchers speculate.

By now you may be wondering how they heck they figured this out.

The researchers looked at data from 672 pairs of adult twins who were interviewed twice, 10 years apart. Some of the twin pairs were identical and had the same genes, and some were fraternal, no more genetically linked than any other siblings. And each pair shared the same environment growing up.

That gave the scientists the opportunity to tease out genetics vs. environment question more reliably than they could have for people who aren't twins.

The fact that genetics are more of a factor in the drinking habits of low-income people supports the widely held belief that the stresses of being poor could trigger genetic vulnerabilities.

And it also suggests that if you want to do research on how genes influence alcohol consumption, lower-income communities would be a good place to start.

But ultimately this study shows the complex, tangled influences on drinking behavior and how they play off each other. With alcohol one of the top 10 risk factors for death, disease and disability worldwide, getting a better grip on risk factors could make it easier to prevent problems and reduce the toll.