A person’s income level may influence how much they drink, a new study suggests. The study found people with lower incomes had more variation in how much they drank, compared with people with higher incomes.

It appears that the low-income group includes more light drinkers and non-drinkers, as well as more heavy drinkers, than the high-income group. People with higher incomes, in contrast, are more likely to drink overall, but they are also more likely to moderate how much alcohol they consume, according to NPR.

The study found genetics play a bigger role in the drinking habits of people with low incomes, while environmental factors were more influential for people who earn higher salaries. The researchers say people in higher-income communities may have more uniform family norms about drinking.

The findings appear in Alcoholism: Clinical and Experimental Research.

The study included 672 pairs of adult twins. They were interviewed twice, 10 years apart. Some of the twins were identical (their genetic material is the same), while others were fraternal (their genetic connection is the same as siblings born at separate times). Each pair shared the same environment growing up.

The researchers say their finding that genetics play a bigger role in the drinking habits of people with low income suggests the stresses of being poor could trigger genetic vulnerabilities for alcohol use.

“Our study’s key finding is that genetic and environmental effects on the amount of alcohol use are not constant across all individuals in the population, but instead vary by the socioeconomic context,” lead researcher Nayla Hamdi of the University of Minnesota said in a news release. She added the findings suggest “genes and environments do not influence alcohol use in isolation but rather in interaction with one another.”