Opioid mortality following implementation of medical marijuana programs (1999-2017) in the United States

Daniel E. Kaufman, Asawer M. Nihal, Janan D. Leppo, Kelly M. Staples, Kenneth L. McCall, Brian J. Piper

BioRxiv preprint, June 14, 2019.

Doi : 10.1101/670059

 

Abstract

The United States is in the midst of an opioid overdose epidemic. A prior report using the Center for Disease Control’s Wide-ranging Online Data for Epidemiologic Research (WONDER) database discovered that opioid overdoses decreased by 24.8% from 1999 to 2010 in states with medical cannabis (MC+) relative to those without (MC-). The present study evaluated any differences following MC legislation on WONDER reported opioid overdoses, corrected for population, from 1999 to 2017 using an interrupted time series. Overdoses were significantly higher in MC+ states from 2012-2017. The slope of opioid overdose deaths over time increased significantly post-implementation in states without MC (3-years Pre = 0.1 + 0.1, 3-years Post = 0.7 + 0.2, t(16) = 2.88, p < .011). Overdose deaths showed a non-significant elevation in states with MC (Pre = 1.3 + 0.3, Post = 2.8 + 0.8, t(11) = 2.01, p = .069). Post-legalization slopes were significantly higher in MC+ than MC- ( t(11.95) = 2.70, p < .05). Overall, any impact of medical cannabis laws on opioid overdoses appears modest. There are other confounds (e.g. death determination reporting quality) which differ non-randomly among states and are non-trivial to account for in ecological investigations of cannabis policy. Alternatively, the potency of fentanyl analogues may obscure any protective effects of MC against illicit opioid harms.

Keywords : Medical marijuana, opioids, overdose, mortality, cannabis

 

Introduction

The US continues to struggle to reverse an opioid overdose crisis. Overdoses involving any opioid increased from eight-thousand in 1999 to approximately nineteen-thousand in 2007 and to almost forty-eight- thousand in 2017 (NIDA, 2019). Overdose data should be interpreted cautiously however as states differ widely in use of medical, or even non-medical, personnel or analytical chemistry procedures to complete death determinations. The number of overdoses where the substance involved was unspecified on the death certificate ranged from 0% in Washington DC to 51% in Pennsylvania (Buchanich et al. 2018). The Centers for Disease Control and Prevention (CDC) used a three-tier system (excellent, good, or other/less than good) to classify overdose death determinations with twenty-two states falling into the latter designation (Rudd et al. 2016). Interestingly, prescription opioid use, a measure with much more homogenous data collection, peaked in 2011 (Piper et al. 2018) and has undergone pronounced reductions for most agents, with the exception of buprenorphine (Collins et al. 2019). Buprenorphine availability is associated with decreased opioid overdoses (Schwartz et al. 2013). States that expanded Medicaid saw a seventy percent increase in buprenorphine prescriptions (Wen et al. 2017).

Several lines of evidence, albeit mostly from non-randomized and non-blind research designs, are suggestive of the potential for medical cannabis (MC) to attenuate opioid use or misuse. The potency of morphine on the rodent tail flick response to an aversive thermal stimuli was greatly enhanced by tetrahydrocannabinol (THC, Smith et al. 1998). Human trials have supported the ability of THC to augment the pain reducing effects of morphine and oxycodone (Abrams et al. 2011; Cooper et al. 2018). Three-quarters of dispensary members reported a reduction in their use of opioids after starting MC (Piper et al. 2017). The 2017 National Academy of Sciences report stated that evidence was conclusive that cannabis reduces chronic pain in adults, but the magnitude of effect was modest (National Academy of Sciences, 2017). Similarly, examination of a prescription drug monitoring program records revealed that patients were seventeen-fold more likely to stop use of all controlled substances after starting MC (Stith et al. 2018). States that legalized MC had lower expenditures for prescription medications in Medicare (Bradford & Bradford, 2016) and Medicaid (Bradford & Bradford, 2017, although see Ozluk, 2017). One of the most impactful studies was on opioid analgesic and heroin overdoses from 1999 – 2010 which made two discoveries. First, states that legalized MC had more opioid overdoses relative to those that did not. Second, opioid overdoses declined following MC implementation relative to those states without MC (Bachhuber et al. 2014). Further examination identified pre-existing state differences in opioid dependence hospitalizations and reductions associated with MC implementation (Shi, 2017). Findings like these (Lucas, 2017) may have been influential in for eight states (Colorado, Illinois, Missouri, Nevada, New Jersey, New Mexico, New York, and Pennsylvania) including opioid misuse as a qualifying condition for medical cannabis (NORML, 2019).

The objective of this report was to provide an update to Bachhuber et al. 2014 and examine opioid overdose mortality with the inclusion of additional states that have approved MC.

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