Guidelines released by the Centers for Disease Control and Prevention (CDC) in 2016 aimed at making opioid prescribing safer may have led to shorter prescriptions with lower doses, a new study suggests.

The guidelines say clinicians treating acute pain should prescribe opioids at the lowest effective dose, and for no longer than the pain is likely to last — three to seven days in most cases.

Researchers analyzed data from 2011 to 2017 on patients with private insurance or a Medicare Advantage plan. None had filled a prescription for opioids in the previous year. The study found the percentage of patients who filled an opioid prescription decreased from almost 12% in 2011 to just over 9% in 2017, HealthDay reports.

Before the CDC released their guidelines, the number of days’ supply in initial prescriptions was increasing. After the guidelines were released, the length of prescriptions decreased 5% in the first year and 10% in the second year.

“These findings, based on trends before and after the CDC guideline was released, show it may have catalyzed other changes, because it came from a trusted entity,” lead author Jason Goldstick, Ph.D., said in a news release. “It’s impossible to isolate the effect of the guideline itself, given all the activity around opioid prescribing, but it’s important to track these trends and use them to inform future efforts to treat pain safely and effectively.”