Opioid abuse has decreased among Medicare recipients in states that require doctors to check patients’ drug history in a prescription drug monitoring database, according to a new study.

While all states have databases to track opioid prescriptions, not all states require healthcare providers to check the databases before writing prescriptions for patients, UPI reports.

The new study found states that required doctors to check the database had a decrease in the number of Medicare recipients who received more than a seven-month supply of opioids in a six-month period. These states also had a decrease in patients who filled a prescription before the previous one had finished. “Doctor-shopping” in these states decreased by 8 percent in Medicare patients who used opioids.

The states with the largest reductions in rates of opioid abuse had the strictest laws. For example, New York requires doctors to check a patient’s opioid history at each visit, the researchers note in the National Bureau of Economic Research.