While illicit drug use has decreased in most large American cities, prescription drug abuse has climbed, according to a new study.

The study evaluated emergency room visits related to drug abuse in 11 major metropolitan areas, and some smaller urban areas, from 2007 to 2009. The researchers found illicit drug use accounted for more emergency department visits than prescription drug abuse in 2007 (26 percent vs. 20 percent), for all metropolitan areas except Phoenix.

From 2007 to 2009, emergency departments reported an 8 percent drop in visits for illicit drug abuse, while visits for prescription drug abuse rose 2 percent, HealthDay reports. In 2009, illicit drug use accounted for 28 percent of ER visits, while prescription drug abuse accounted for 22 percent.

The findings were presented this week at the annual meeting of the American Society of Anesthesiologists.

“The harsh reality is prescription drug abuse has become a growing problem in our society,” study author Dr. Asokumar Buvanendran of Rush University Medical Center in Chicago, said in a news release. “We hope the results of this study will aid physicians in effectively treating patients who struggle with prescription drug abuse, as well as encourage widespread patient education about the safe use, storage and disposal of medications.”