Opioid-related harm, including overdose deaths, has reached epidemic proportions. This study used a difference-in-differences analysis to examine whether a policy approach could reduce harm from opioid misuse. Investigators compared states with and without mandated provider review of drug monitoring data. In states with mandated review, opioid prescribers must check whether patients are receiving opioids from multiple prescribers and identify the total prescribed opioid dose. States with mandated review policies had fewer opioid overdose deaths and lower amounts of opioids prescribed than states without mandated prescriber review. These results are consistent with a prior study that established the benefit of prescription drug monitoring programs. The authors assert that despite the effectiveness of this policy, more interventions are needed to enhance opioid safety, as suggested in a recent study. A previous WebM&M commentary described opioid-related harm.