Full length articleMedical marijuana policies and hospitalizations related to marijuana and opioid pain reliever
Introduction
As voters in Arkansas, Florida, and North Dakota approved the ballots for medical marijuana legalization in November 2016 (Christensen and Senthilingam, 2016), approximately 60% of the population in the U.S. now lived in states that permitted marijuana use for medical purpose. Despite the increasing support from the public, the scientific research on the public health impacts of medical marijuana legalization has not reached a consensus. Existing evidence primarily concentrated on the changes in the prevalence of marijuana use and provided mixed findings (Sznitman and Zolotov, 2015). The use prevalence, however, is arguably not the greatest public health concern. While occasional use is not without health risks, marijuana is most harmful to regular users and early initiators and largely harmless to most occasional users (Hall, 2009). Research on stronger indicators of adverse effects of medical marijuana legalization is needed. Given that marijuana is not directly associated with mortality (Sidney et al., 1997), hospitalization probably represents one of the most serious health consequences of marijuana, which imposes substantial economic burdens to the healthcare system and the society (Pacula et al., 2008). No previous studies have investigated how medical marijuana policies were associated with marijuana-related hospitalizations.
In parallel to the heated debate on marijuana legalization, there were overwhelming concerns about the epidemic of opioid pain reliever (OPR) abuse and overdose. In the last two decades, the mortality rate related to OPR overdose and the quantity of prescribed OPR at least quadrupled in the U.S. (CDC, 2011, Warner et al., 2014). In 2014, more than 14,000 deaths were related to OPR overdose (CDC, 2016). States have advocated or adopted a series of policies to combat this increasing trend, such as prescription drug monitoring programs and regulations of pain management clinics. The positive effects of these policies on reducing OPR-related outcomes were reported by some studies (Bao et al., 2016, Dowell et al., 2016, Kennedy-Hendricks et al., 2016, Lyapustina et al., 2016, Patrick et al., 2016) but not all (Li et al., 2014, Paulozzi et al., 2011).
Recent studies started to investigate whether medical marijuana legalization would have any influences on the OPR abuse and overdose epidemic. Marijuana has therapeutic effects for chronic pain (Lynch and Ware, 2015) and is being used by patients prescribed with OPR. Around 14–33% patients prescribed with OPR were screened with cannabinoid-positive results (Reisfield et al., 2009). If the patients with legitimate prescriptions for OPR were substituting OPR partially or entirely with marijuana, the increased availability of marijuana as a result of medical marijuana legalizations may reduce the risks of OPR-related health consequences. On the other hand, marijuana use for recreational purpose may serve as a gateway drug to OPR and increase the risk of OPR initiation (Hall and Lynskey, 2005). Should medical marijuana policies have any impacts on marijuana use for medical or recreational purpose, they may unintentionally lead to changes in OPR use and related hospitalizations. Four recent studies reported reduced OPR-related outcomes in association with medical marijuana legalization (Bachhuber et al., 2014, Bradford and Bradford, 2016, Kim et al., 2016, Powell et al., 2015), but the evidence is still limited.
The objective of this study is to examine the associations between medical marijuana legalization and hospitalizations related to marijuana and OPR. Using state-level administrative records of hospital discharges from 1997 to 2014, we focused on the severe health consequences of medical marijuana legalization and exploited the variations of policy implementation in different states at different times. This study is expected to add to the still-limited literature regarding the intended and unintended impacts of medical marijuana legalization and provide implications to OPR policymaking.
Section snippets
Data
Annual state-level hospitalization data were obtained from the State Inpatient Databases (SID). Developed for Healthcare Cost and Utilization Project (HCUP) and sponsored by the Agency for Healthcare Research and Quality (AHRQ), the SID provide administrative records of hospital discharges in community hospitals in participating states. The SID cover the universe of non-federal, short-term, general and other specialty hospitals, regardless of funding sources, as well as the universe of
Descriptive statistics
Fig. 1 demonstrated time trends of hospitalization rates without any adjustment. During 1997–2014, the average hospitalization rates related to marijuana and OPR increased dramatically by approximately 300% in states that did or did not implement medical marijuana policies. In these 18 years, the average hospitalization rates increased from 4.49 to 16.04 per 1000 discharges for marijuana dependence and abuse, from 5.14 to 15.15 per 1000 discharges for opioid dependence and abuse, and from 0.47
Discussion
Using state-level administrative hospitalization data during 1997–2014, we found no convincing evidence that the implementation of medical marijuana policies was associated with a subsequent increase in marijuana-related hospitalizations. This result was robust to the key policy dates defined in different ways. In conjunction with the studies that demonstrated negative or null associations of medical marijuana policies to substance abuse treatment admissions (Pacula et al., 2014b), suicide
Conclusions
While the interpretation of the results should remain cautious, this study suggested that medical marijuana policies were not associated with marijuana-related hospitalizations. Instead, the policies were unintendedly associated with substantial reductions in OPR-related hospitalizations. It is still premature to advocate medical marijuana legalization as a strategy to curb the OPR abuse and overdose epidemic, but the policymakers should take into consideration these positive unintended
Role of funding source
This research was supported by grant R01DA042290 (PI: Shi) from the National Institute on Drug Abuse. This article is the sole responsibility of the author and does not reflect the views the National Institute on Drug Abuse.
Contributors
Y.S. conceived and designed the study, retrieved data, conducted analysis, interpreted findings, and wrote the manuscript.
Conflict of interest
No conflict declared.
Acknowledgment
I thank research assistant Sumin Wang for the help with data assembling.
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