Recreational marijuana laws and the misuse of prescription opioids: Evidence from National Survey on Drug Use and Health microdata

United States marijuana legalization and opioid mortality trends before and during the first year of the COVID-19 pandemic

BACKGROUND

To determine if marijuana legalization was associated with reduced opioid mortality.

STUDY DESIGN

The United States (US) opioid mortality trend during the 2010-2019 decade was compared in states and District of Columbia (jurisdictions) that had implemented marijuana legalization with states that had not. Acceleration of opioid mortality during 2020, the first year of the coronavirus disease 2019 (COVID-19) pandemic, was also compared in recreational and medicinal-only legalizing jurisdictions.

METHODS

Joinpoint methodology was applied to the Centers for Disease Control and Prevention WONDER data. Trends in legalizing jurisdictions were cumulative aggregates.

RESULTS

The overall opioid and fentanyl death rates and the percentage of opioid deaths due to fentanyl increased more during 2010-2019 in jurisdictions that legalized marijuana than in those that did not (pairwise comparison p = 0.007, 0.05, and 0.006, respectively). By 2019, the all-opioid and fentanyl death rates were 44 and 50 percent greater in the legalizing than in the nonlegalizing jurisdictions, respectively. When the COVID-19 pandemic hit in 2020, jurisdictions that implemented recreational marijuana legalization before 2019 had significantly greater increases in both overall opioid and fentanyl death rates than jurisdictions with medicinal-only legalization. For all-opioids, the mean (95 percent confidence interval) 2019-to-2020 increases were 46.5 percent (36.6, 56.3 percent) and 29.1 percent (20.2, 37.9 percent), respectively (p = 0.02). For fentanyl, they were 115.6 percent (80.2, 151.6 percent) and 55.4 percent (31.6, 79.2 percent), respectively (p = 0.01).

CONCLUSIONS

During the past decade, marijuana legalization in the US was associated at the jurisdiction level with a greater acceleration in opioid death rate. An even greater increase in opioid mortality occurred in recreational-legalizing jurisdictions with the onset of the COVID-19 pandemic. Marijuana legalization is correlated with worsening of the US opioid epidemic.

Impact of Δ9-Tetrahydrocannabinol and oxycodone co-administration on measures of antinociception, dependence, circadian activity, and reward in mice

Oxycodone is commonly prescribed for moderate to severe pain disorders. While efficacious, long-term use can result in tolerance, physical dependence, and the development of opioid use disorder. Cannabis and its derivatives such as Δ9-Tetrahydrocannabinol (Δ9-THC) have been reported to enhance oxycodone analgesia in animal models and in humans. However, it remains unclear if Δ9-THC may facilitate unwanted aspects of oxycodone intake, such as tolerance, dependence, and reward at analgesic doses. This study sought to evaluate the impact of co-administration of Δ9-THC and oxycodone across behavioral measures related to antinociception, dependence, circadian activity, and reward in both male and female mice. Oxycodone and Δ9-THC produced dose-dependent antinociceptive effects in the hotplate assay that were similar between sexes. Repeated treatment (twice daily for 5 days) resulted in antinociceptive tolerance. Combination treatment of oxycodone and Δ9-THC produced a greater antinociceptive effect than either administered alone, and delayed the development of antinociceptive tolerance. Repeated treatment with oxycodone produced physical dependence and alterations in circadian activity, neither of which were exacerbated by co-treatment with Δ9-THC. Combination treatment of oxycodone and Δ9-THC produced CPP when co-administered at doses that did not produce preference when administered alone. These data indicate that Δ9-THC may facilitate oxycodone-induced antinociception without augmenting certain unwanted features of opioid intake (e.g. dependence, circadian rhythm alterations). However, our findings also indicate that Δ9-THC may facilitate rewarding properties of oxycodone at therapeutically relevant doses which warrant consideration when evaluating this combination for its potential therapeutic utility.