Did Drug Decriminalization Increase Overdoses

We study the effect of drug decriminalization on overdose mortality using Oregon's Measure 110 and Washington's Blake decision. Synthetic-control estimates show that both decriminalization regimes sharply reduced drug arrests and were followed by sustained increases in overdose mortality relative to matched counterfactuals. The estimates imply approximately 1,186 excess deaths in Oregon and 1,895 in Washington from 2021 through 2023. We also revisit the role of fentanyl supply shocks. A fentanyl-share control may partly capture enforcement-driven declines in non-fentanyl NFLIS reports, while alternative fentanyl measures leave positive overdose effects.