The study publishes in the Sept. 30 issue ofJAMA Internal Medicine.

"Alcohol use is a well-established risk factor for firearm violence," said Rose Kagawa, assistant professor of emergency medicine and first author of the VPRP study. "Our study suggests that handgun purchasers with a DUI conviction on their record at the time of purchase have a higher incidence of future violence and crime compared to purchasers without DUI convictions."

For the study, the VPRP team used the California Department of Justice Dealer's Record of Sale database to identify everyone aged 21 to 49 who legally purchased a handgun in California in 2001. The age range reflects the facts that handgun purchasers in California must be at least 21 years of age, and criminal behavior among persons aged 50 and older is relatively low.

Using records from the California Department of Justice Criminal History Information System, they identified arrests for violent crimes following the first purchase in 2001 (+10 days to account for California's waiting period) until the end of 2013 or until they could no longer confirm the purchaser was alive and residing in California. Those with at least one DUI conviction on their record at the time of purchase were compared to those without.

"Of the 78,878 handgun purchasers in California whose criminal records we tracked during 13 years, 9% of purchasers with pre-existing DUI convictions were later arrested for murder, rape, robbery or aggravated assault. This is compared to 2% of purchasers with no prior criminal history at the time of purchase," Kagawa said. "When we compared purchasers who only had DUI convictions and no other arrests or convictions with those who had no criminal history, a DUI conviction was associated with more than double the risk of future arrest for a violent crime."

California law prohibits individuals convicted of certain violent misdemeanors from legally purchasing a handgun within 10 years of conviction. As a result, they were not included in the study.

The study expands on VPRP research published in 2018 that used data on handgun purchases in 1977 and tracked arrests for violent or firearm-related crimes through 1991. While the sample size included only 4,066 purchasers, that study also associated risky alcohol use, mainly DUI offenses, with arrests for future violent crimes.