Between 2006 and 2017, 223.7 million opioid prescriptions were filled each year, according to a new study in the Journal of the American Medical Association. Opioid prescription rates annually rose to a peak in 2010, then declined steadily through 2017, according to the Journal. Overall, opioid prescriptions decreased by 13% over the evaluated period.

While that might be good news at first blush, the researchers who evaluated prescriptions during the period found that physicians are keeping patients on opioids for longer periods.

In one study, the researchers, whose findings were earlier reported on by Axios, found that short-duration prescriptions of fewer than 30 days, increased from an average period of 13 days to 17.9 days between 2006 and 2017. Longer-duration prescriptions lasting 30 days or longer rose from 18.3% of opioid prescriptions to 24.9% of opioid prescriptions. Both findings were considered “statistically significant,” according to the researchers.

Opioid use has quickly become one of the more concerning health issues in the U.S. Opioids, which are often prescribed legally as pain medication, can be extremely addictive and easily abused. Opioid addiction and overdoes are soaring across the U.S. and in some cases, are caused by legally obtained drugs.

In response, some states have called on doctors to consider alternative pain management options, including medical marijuana, which has been assigned an opioid replacement by several states, including New York and Illinois, among others.

The researchers said in their findings that the reduced rate of prescriptions suggests doctors are taking heed of those warnings and prescribing fewer opioids. But longer opioid use has been tied to a higher chance of addiction and overdose.