States that perform local-level background checks for firearms purchases are more effective in reducing firearm suicide and homicide rates than states that rely only on a federal-level background check, according to a new study by researchers at the Medical College of Wisconsin in Milwaukee.

There are three entities that perform background checks for firearm purchases. The FBI, a single state agency or a local law enforcement department such as a municipal police or sheriff's office are the bodies contacted to perform background checks.

All states consult the National Instant Criminal Background Check System (NICS), which scans federal databases. This is the minimum background check that must be performed. States that use state and local checks have access to the same information available to the FBI, as well as information that is available only to state agencies.

The researchers associated local-level background checks with a 27 percent-lower firearm suicide rate and a 22 percent-lower homicide rate in adults aged 21 years or older.

The retrospective study observed the association between the Department of Justice classification of agencies conducting firearm background checks for each state from 2002 to 2004, and firearm suicide and homicide rates for the same years from the National Center for Injury Prevention and Control.

Federal minimums for gun-control laws were established in 1993 with the passage of the Brady Handgun Violence Prevention Act.

The Brady Act disqualifies any persons from purchasing firearms who:

Are under indictment or convicted of a crime punishable by more than one year in prison;

Are a fugitive from the law;

Are unlawfully a user of a controlled substance;

Have been adjudicated as mentally defective or committed to a mental institution;

Have been dishonorably discharged from the armed services;

Have renounced United States citizenship;

Are subject to a restraining order;

Have been convicted of domestic violence.

"Depending on which agency is conducting the background check, additional records may be accessed, resulting in a more detailed and effective check," says Dr. Peter Layde, M.D., professor of population health and co-director of the Injury Research Center at the Medical College.

Federal-level background checks are used as the only level of background checks in 21 states. Seventeen states use state-level background checks in addition to the federal checks. Only 12 states rely on local-level background checks, which consult local law enforcement offices, such as a sheriff's department, in addition to the federal system.

States that performed only federal-level checks saw a firearm suicide rate of 11.64 people per every 100,000 in the population. States that performed state-level or local-level checks were found to have substantially lower rates of firearm suicides, at 8.45 and 5.74 per 100,000, respectively.

A similar trend was observed with firearm homicide rates, with 4.28 per 100,000 for federal checks; 4.02 per 100,000 for state checks; and 2.81 per 100,000 for local checks.

"As with suicides, the reduction in firearm homicide rates associated with local-level background checks, if confirmed, would also have an important impact on public health and economic outcomes," says Dr. Layde. "Assaults involving a firearm are more lethal and more costly for patients and hospital systems than non-gun assaults."

"This is the first study to analyze the effects of differences among states doing background checks for firearm purchase," explains Dr. Layde. "We hope that future research will evaluate the impact of changes in the background checking process that may emerge in the next few years."

The study was funded in part by a grant from the Centers for Disease Control and Prevention.

The study was led by Steven A. Sumner, B.S., a third-year medical student, along with Layde and Clare Guse, M.S., biostatistician in the Injury Research Center and the department of family and community medicine at the Medical College. It is published electronically in the May 2008 issue of the American Journal of Preventive Medicine, ahead of print.