Introduction: In February 2021, the state of Oregon in the USA decriminalized possession of opioids, but in March 2024, this law was reversed over concerns that the change in legal status of this drug had exacerbated the opioid overdose epidemic in the state. This legal change has not been adequately studied, and in the context of a rise in opioid overdose deaths across the USA beginning about five years before the decriminalization of opioid use in Oregon, it is possible that the rise in overdose deaths that occurred after February 2021 was unrelated to the legal change. Materials and methods: This study uses two methods to identify the most likely point at which opioid overdose deaths began to rise in Oregon, using Centers for Disease Control (CDC) Wonder mortality data. It then applies a difference-in-difference (DiD) model to opioid overdose deaths in Oregon and its neighboring states to assess whether the decriminalization of opioid use was associated with increased overdose mortality. Results: We identified the most likely changepoint in the opioid overdose trend in Oregon as occurring in December 2019, almost 18 months before decriminalization, and found that all but one neighboring state experienced similar changes in opioid overdose mortality after Oregon, and before the decriminalization took place in Oregon. Conclusions: Our DiD model found no significant difference in mortality in Oregon compared to neighboring states, indicating that decriminalization did not have a statistically observable impact on opioid overdose deaths in Oregon.
Gilmour et al. (Tue,) studied this question.