Women who became adults when 18 was the legal drinking age in the United States are at higher long-term risk for homicide and suicide, than women who grew up after the legal drinking age became 21, a new study finds.

The study followed Americans who became adults before 1984, when a federal law went into effect that established the legal drinking age as 21. During the 1960s and 1970s, many states lowered the drinking age to 18 to match the age for military service and voting, HealthDay reports. A rise in drunk driving deaths led to the law that raised the drinking age to 21 around the country.

The researchers looked at data on 200,000 suicides and 130,000 homicides that occurred between 1990 and 2004. They focused on 39 states where the drinking age was raised to 21. In 37 of the 39 states, they found women who grew up when drinking below age 21 was legal had a 12 percent higher risk for suicide, than women who grew up after 21 was the legal drinking age.

In 38 of the 39 states, women who grew up when the legal drinking age was below 21 had a 15 percent higher risk of dying from homicide, compared with women who came of age when 21 was the legal drinking age. These trends were not seen among men.

Raising the drinking age to 21 has prevented up to 600 suicides and 600 homicides per year, the researchers estimate.

“We suspected that adolescence is a unique period in terms of the brain’s response to alcohol and the vulnerability for addiction,” lead researcher Richard Grucza said. “And, in fact, what we have here is a natural experiment that supports that idea, by demonstrating an unintended but positive consequence that comes from having raised the drinking age.”

The study appears in the journal Alcoholism: Clinical & Experimental Research.