Since its enactment, however, M110 has faced implementation challenges, and addiction treatment capacity has not sufficiently expanded to meet the state’s needs. Police officials reported that decriminalization hampered their ability to address concerns about public drug use. In 2021, Oregon’s rate of fatal overdoses increased by approximately 50 percent compared with the previous year. In response to these initial outcomes, Oregon’s legislature recriminalized drug possession in March 2024, which took effect in September 2024. As other jurisdictions look to Oregon’s health outcomes in considering their own policy responses to overdoses, an accurate assessment of the association between M110 and fatal overdoses is crucial.
Prior studies have attempted to provide this assessment, but none have fully accounted for the introduction of illicitly manufactured fentanyl. However, the rapid spread of fentanyl in illicit drug markets has dramatically increased overdose deaths. As fentanyl spread throughout the nation, the overdose fatality rate involving synthetic opioids other than methadone, which includes fentanyl, increased from 1.8 per 100,000 people in 2014 to 21.8 in 2021, a 1,100 percent increase. However, fentanyl did not saturate each state’s illicit drug market at the same time. Beginning in 2013, it spread from east to west and reached Oregon in the first half of 2021—around the same time as when M110 became effective on February 1, 2021.
Our study attempts to disentangle the effects of decriminalization on fatal overdoses from the rapid spread of fentanyl. We compared fatal overdose rates in Oregon with those in all other states and Washington, DC, (except Washington State) after accounting for the gradual spread of fentanyl across the nation. Our study models what Oregon’s overdose rate would have looked like in 2021 and 2022 had decriminalization not occurred using data from 2008 to 2022. Mortality data came from the Centers for Disease Control and Prevention, and data on the composition of illicit drug supplies in each state came from the National Forensic Laboratory Information System, which reports the percentage of drug seizures that were for fentanyl or related substances in each state.
Our research finds a positive association between decriminalization and fatal overdose rates in Oregon before accounting for the introduction of fentanyl. However, accounting for fentanyl eliminates this positive association and suggests that M110 may have had no effect on fatal overdoses. Specifically, our estimates indicate that M110 may have caused as many as 289 fewer deaths or as many as 117 excess deaths in Oregon in 2021 and 2022; our findings allow us to rule out larger effects in either direction.
It is important to consider whether decriminalization itself increased the supply of illicit fentanyl by altering the incentives of suppliers or users. However, our findings reveal that the four states bordering Oregon (Washington, Idaho, Nevada, and California) experienced a surge in fentanyl during the same period as Oregon. This suggests that the introduction of fentanyl into Oregon’s illicit drug supply would have happened regardless of M110.
We did not include Washington State in the comparison group because its supreme court effectively decriminalized drug possession for four months between February 2021 (when it struck down the state’s drug possession law) and July 2021, when misdemeanor recriminalization took effect. Instead, we analyzed the effect of decriminalization in Washington. Similar to Oregon, our findings suggest that decriminalization was positively associated with fatal overdoses before accounting for the introduction of fentanyl, and the association disappears after accounting for fentanyl. Additionally, we found that recriminalization of drug possession in Washington was not associated with reductions in overdose deaths. Rather, fatal overdose rates accelerated in the months after recriminalization. This suggests that Oregon’s recriminalization may not reduce the overdose rate, given the presence of fentanyl in the state’s illicit drug market.
Our study is the first, to our knowledge, to evaluate the effect of M110 on fatal overdoses while accounting for the introduction of fentanyl in Oregon’s illicit drug market. Our findings suggest that the increase in the state’s fatal drug overdose rate after the implementation of M110 should not be attributed to drug decriminalization. Instead, the state’s contemporaneous transition to a fentanyl-based illicit drug market is a more plausible explanation.
