A new study finds marijuana use among U.S. teens dropped dramatically over a decade, from 23.1% in 2011 to 15.8% in 2021.

Teens in all grades experienced a notable decrease in current marijuana use, especially among ninth graders, HealthDay reports. The percentage of teens who tried marijuana for the first time before age 13 also notably decreased – from 8.1% in 2011 to 4.9% in 2021.

Researchers from Florida Atlantic University reviewed data from the Youth Risk Behavior Survey between 2011 and 2021, which surveyed 88,183 teens in grades nine through 12. They said one of the most significant findings is the shift in trends by gender, with girls surpassing boys in reported marijuana use by 2021. In 2021, girls reported a higher prevalence of current marijuana use (17.8%) than boys (13.6%). This marks a significant change from 2011 when boys were more likely to use marijuana (25.9%) compared to girls (20.1%).

Senior researcher Panagiota Kitsantas said the findings suggest that as teens advance through high school, they may have greater access to marijuana, influenced by more developed peer networks and increased independence. “This trend highlights the need for targeted interventions aimed at older adolescents, who are at a greater risk of regular marijuana use,” Kitsantas said in a university news release.