Drug decriminalization, the introduction of fentanyl to drug markets, and fatal overdose in Oregon
Authors: Zoorob Michael , Park Ju Nyeong , Kral Alex H. , Lambdin Barrot H. , del Pozo Brandon 
Published: April 2024

ABSTRACTImportanceWith the implementation of Measure 110 (M110), Oregon became the first state in the United States to decriminalize small amounts of any drugs for personal use. No analysis of the effect of this law on overdose mortality has fully accounted for the introduction of fentanyl to Oregon’s unregulated drug market, a substance known to drive fatal overdose rates.ObjectiveTo evaluate whether the decriminalization of drug possession in Oregon was associated with changes in fatal drug overdose rates after accounting for the rapid escalation of fentanyl in Oregon’s unregulated drug market.Design, Setting, and ParticipantsThe association between fatal drug overdose and enactment of M110 was analyzed using a matrix completion synthetic control method. The control group consisted of the 48 US states and Washington DC that did not decriminalize drugs. The rapid escalation of fentanyl in unregulated drug markets was determined using the state-level percentage of all samples reported to the National Forensic Laboratory Information System that were identified as fentanyl or its analogs. A changepoint analysis was used to determine when each state experienced a rapid escalation of fentanyl in its unregulated drug market, which was included as a covariate. Mortality data were obtained from the Centers for Disease Control and Prevention from 2008-2022.ExposuresM110 took effect on February 1, 2021.Main OutcomeFatal drug overdose rates per half-year.ResultsAnalysis indicated a rapid escalation of fentanyl in Oregon’s unregulated drug supply occurred in the first half of 2021, contemporaneous with enactment of M110. The crude association between decriminalization and fatal overdose rate per 100,000 per half-year was significant (Tau = 1.83; SE = 0.39; p < 0.001); however, adjusting for rapid escalation of fentanyl as a confounder, the effect of drug decriminalization on overdose mortality in Oregon was null (Tau = −0.51; SE = 0.36). Sensitivity analyses were consistent with this result.Conclusions and RelevanceAfter adjusting for the rapid escalation of fentanyl, analysis found no association between M110 and fatal drug overdose rates. Future evaluations of the health effects of drug policies should account for changes in the composition of unregulated drug markets.Key PointsQuestionWhat was the association between the Oregon’s 2021 law that decriminalized drug possession and overdose mortality when accounting for the spread of fentanyl through the state’s unregulated drug market?FindingsIn this longitudinal synthetic control study, fentanyl’s rapid spread through Oregon’s unregulated drug market occurred contemporaneously with the state’s decriminalization of drug possession. An analysis that accounted for fentanyl’s introduction to the drug supply showed that decriminalization was not associated with an increase in fatal drug overdose rates in Oregon in the two years after its enactment.MeaningWhen evaluating the effect of public policies on overdose mortality, it is critical to account for the role of fentanyl as the principal driver of the nation’s overdose mortality epidemic. After accounting for the spread of fentanyl to Oregon, there was no association between decriminalizing drug possession and changes in the state’s fatal drug overdose rate.