Jayani Jayawardhana, PhD, is an associate professor at the University of Georgia College of Pharmacy (@JayJayawardhana). Jose M. Fernandez, PhD, is an associate professor at the University of Louisville College of Business (@UofLEcon).
Before the COVID pandemic, the United States was in the midst of an opioid epidemic. A menu of health policies has been recommended to battle the rising cases of opioid overdoses including prescription drug monitoring programs (PDMPs), increasing access to naloxone (an opioid antagonist), and pain management clinic laws. Surprisingly, another set of policies adopted by some states—though not intended as a response to the opioid epidemic—was found to be effective in reducing opioid prescriptions: medical marijuana policies (MMPs).
A new study, published this month in Health Services Research, contributes to the literature on medical marijuana by examining the relationship between medical marijuana policies and hospitalizations and emergency department (ED) visits related to opioids while accounting for different types of medical marijuana policies.
Medical marijuana policies take different forms, including permitting active dispensaries to sell medical marijuana and allowing home cultivation of medical marijuana. These policies differ in how much access they afford patients. Access contingent on dispensaries often means needing to register as a patient, gaining access to medical marijuana card, and being able to afford the cost of medical marijuana since it is not covered through health insurance. Furthermore, dispensaries may not be easily accessible for all users.
Home cultivation provides easier access to marijuana by allowing patients to grow marijuana at home. Although home cultivation policies may limit the number of plants that can be grown and the maturity level of plants at a given household, home cultivation provides access to marijuana at almost no cost except for the initial cost of purchasing plants/seeds for cultivation.
Previous literature has emphasized the importance of accounting for these specific types of policies when studying medical marijuana since they are different from each other. Existing research on MMPs have found states with home cultivation of medical marijuana only to be associated with reductions in opioid prescriptions among Medicare enrollees. While a few studies have found MMPs to be associated with reductions in opioid-related mortality, opioid-related hospitalizations, and opioid prescriptions among Medicaid enrollees, these studies have not accounted for different types of MMPs.
We used state-level quarterly data from Healthcare Cost and Utilization Project’s Fast Stats database to gain access to ED and inpatient visit rates by state. These data were linked with changes in medical marijuana polices in states from 2005 to 2016. Along with the medical marijuana polices, we controlled for a long list of state policies used to combat the opioid crisis including presence of PDMP, mandatory access of PDMP by providers, pain management clinic laws, Good Samaritan laws, availability of naloxone without a prescription, recreational marijuana policy implementation, and Medicaid expansion. In addition, we controlled for state socio-demographic characteristics such as unemployment rate, percent uninsured, population size, median household income, ethanol consumption per capita, and beer taxes.
We used a difference-in-differences regression approach to compare changes in opioid-related inpatient and ED visit rates per 100,000 population before and after a state has implemented a given MMP to those states that did not implement the given MMP. A key identifying assumption was that parallel trends existed in inpatient and ED visit rates among states that implemented MMPs (treatment) and states that did not implement MMPs (control) prior to policy implementation; an event study showed no significant difference between treatment and control groups prior to policy implementation.
The results of our study showed that states that allow home cultivation of medical marijuana experienced about 12% increase in opioid-related hospitalizations and about 44% increase in opioid-related ED visits compared with states without home cultivation of medical marijuana. However, study results did not find significant associations between medical marijuana dispensaries and opioid-related hospitalizations and ED visits.
We further disaggregated home cultivation into two categories, unsupervised and requiring a permit. We found unsupervised home cultivation to be associated with an increase of 15.6% in inpatient hospitalizations related to opioids though requiring a permit for home cultivation was not significantly associated with hospitalizations. These findings indicate that easier access to marijuana through unsupervised home cultivation may result in adverse health outcomes needing further treatment.
Additionally, implementation of recreational marijuana policy was associated with about 16-17% increase in opioid-related hospitalizations, while it had no significant association with opioid-related ED visits. Access to naloxone without a prescription was significantly associated with an 8% increase in opioid-related hospitalizations though it was not significantly associated with opioid-related ED visits. While naloxone may help reduce mortality by reversing opioid overdoses, individuals that experience overdoses may seek healthcare at inpatient setting. Thus, it is not surprising that availability of naloxone is associated with increased opioid-related hospitalizations.
There are a few limitations in this study. The study uses state-level aggregated data for inpatient and ED visits from only 47 states and 35 states respectively for the period of 2005-2016. Identifying specific reasoning behind opioid-related hospitalizations and ED visits or the source of drugs such as prescription or illicit (i.e., heroin) that resulted in those visits was not possible due to the aggregate nature of the data.
Despite these limitations, the findings of this study provide an important contribution to the policy debate on medical marijuana legalization. The findings indicate that increased access to marijuana via home cultivation is associated with increases in opioid-related hospitalizations and ED visits, suggesting that easier access to marijuana among opioid users may result in adverse health conditions that need treatment at inpatient or ED settings.
While it remains unclear whether marijuana liberalization may be a beneficial public health tool in the fight against the opioid epidemic, the results of this study support the argument that potential benefits and adverse health outcomes associated with different types of MMPs should be taken into consideration when discussing marijuana as a policy alternative in addressing the opioid epidemic.