The mechanisms for the causal connections between marijuana and OPR are not clear

It appears that the gaps in hospitalizations involving marijuana dependence and abuse were continuously widened between the states adopting and non-adopting medical marijuana policies with states adopting medical marijuana policies increased more sharply. Throughout the study period, the states with medical marijuana policies continuously had higher rates of hospitalizations related to opioid dependence or abuse. Hospitalization rates related to OPR overdose were originally higher in the states with medical marijuana policies, but increased less rapidly compared to the states without medical marijuana policies. Table 1 reports the associations of hospitalizations to the indicator of medical marijuana policy implementation, controlling for time-varying marijuana-related policies, state-level socioeconomic factors, and state and year fixed effects. The implementation of medical marijuana policies did not have any significant associations with hospitalizations related to marijuana dependence or abuse. However, it was associated with a 23% reduction in hospitalizations related to opioid dependence or abuse and a 13% reduction in hospitalizations related to OPR overdose . In Table 2, the first column for each outcome variable evaluates the indicator of medical marijuana dispensaries. Relative to generic implementation of medical marijuana legalization,plant growing rack the operation of medical marijuana dispensaries had comparable associations with hospitalizations related to opioid dependence or abuse and OPR overdose .

The second column for each outcome variable reports results including both the indicator of medical marijuana policy and the indicator of medical marijuana dispensaries. Medical marijuana dispensaries alone did not have any independent associations with any hospitalization outcomes after indicators for medical marijuana policy implementation were also included in the regressions. In Table 3, we explored if any policy effects could be detected in the periods prior to the implementation year of medical marijuana policies. We found no evidence that hospitalization rates of any category differed between states adopting and non-adopting medical marijuana policies in the pre-policy periods. Table 3 also assesses the presence of dynamic policy effects after the implementation year. We found that the reduction in hospitalizations related to opioid dependence or abuse was most salient after 1 year of policy implementation , whereas the reduction in hospitalizations related to OPR overdose was observed in the third year after policy implementation . With respect to other policy and socioeconomic covariates, uninsured rate was associated with increased OPR overdose hospitalizations. Other covariates including marijuana decriminalization, prescription drug monitoring program, and pain management clinic regulations were generally not associated with any hospitalization outcomes. 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 , suicide rates , and crime rates , our study counters the arguments about the severe health consequences that legalizing medical marijuana may bring to the public health.

It should be noted that this study does not necessarily contradict some prior research that reported an increase in marijuana use prevalence in association with medical marijuana policies . It just appears that, even if legalization resulted in an increase in the prevalence, it did not contribute to the severe health consequences that concern the public the most. Whether such findings hold in the long term needs further monitoring and investigations. This study demonstrated significant reductions in OPR-related hospitalizations associated with the implementation of medical marijuana policies. These findings were supported by the recent studies that reported reduced prescription medications , OPR overdose mortality , opioid positivity among young and middle aged fatally injured drivers , and substance abuse treatment admissions in association with medical marijuana legalization. As mentioned earlier, using marijuana can lead to either an increase or a reduction in OPR use depending on the use purposes and the underlying assumptions. This study appears to support the hypothesis that patients prescribed with OPR substitute OPR with marijuana, but it is not directly testable in our data. An alternative explanation for the results reported in this study is that states with medical marijuana legalization may also have tough OPR prescription regulations. However, this hypothesis was not supported by the null associations of OPR prescription regulations estimated in this study. Future empirical evaluations are warranted to explore the use pattern of OPR and marijuana and substantiate the substituting and gateway effects of the two drugs. Consistent with prior research , policy effects reported in this study were not static. We found reductions in OPR-related hospitalizations immediately after the year of policy implementation as well as delayed reductions in the third post-policy year. Nonetheless, the availability of medical marijuana dispensaries was not independently associated with hospitalizations as suggested by other studies .

A possible interpretation is that only 1 state in our data legalized medical marijuana but did not have operating medical marijuana dispensaries; a few other states opened medical marijuana dispensaries within only 1–2 years after the legalization of medical marijuana. The lack of variations in policy adoption and timing limited our ability to detect independent effects of detailed policy provisions of medical marijuana legalization. The 300% increase in hospitalization rates related to marijuana is striking. In contrast, the past-month prevalence of marijuana use increased at a much slower rate from 6% in 2002 to 7.5% in 2013 . It is unclear what factors have been driving the huge discrepancies between the trends of use prevalence and the trends of hospitalization rates. Although quite a few states legalized medical marijuana or decriminalized marijuana, this study suggested that they did not contribute to the rise of marijuana-related hospitalizations. One alternative hypothesis is the escalation in marijuana potency , which has tripled from 4% in 1995 to 12% in 2014 in the U.S. . Nonetheless, empirical evidence again did not find any associations between the potency increase and the legalization of medical marijuana . Studies to understand the growing market share of high-potency marijuana and its associations with marijuana-related hospitalizations are urgently needed. The unprecedented increase in OPR-related hospitalization rates and other related health outcomes has become a major public health crisis. Compared to the limited research on marijuana, OPR abuse and overdose epidemic has been relatively well studied. It is largely driven by the liberalization of OPR prescription for the treatment of chronic non-cancer pain . Despite lack of evidence in this study,indoor vertical garden system prescription drug monitoring programs and pain management clinic regulations have shown promises to tackle the OPR crisis in some other studies . If the causal relationship indicated in this study can be substantiated in future research, medical marijuana legalization and regulationmay be considered as an alternative strategy to reduce OPR-related hospitalizations without aggravating the adverse consequences related to marijuana.

Our study was subject to several limitations, most of which were related to the data used. First, some states included hospitalization records in the SID from non-community hospitals such as psychiatric facilities and Veterans Affairs hospitals, but some states did not . States may also vary on ICD-9-CM coding practice particularly for drug dependence, abuse, and overdose cases. The coding of opioid dependence or abuse may include heroin cases. The inclusion of state fixed effects should to some extent alleviate these biases in the reporting. Second, the aggregate SID data represented the total number of discharges but not the total number of patients because a patient may be admitted to hospital more than once in a year. The public-use SID were not available before 1997 and not all states participated in the SID during the study period. The findings may not be generalizable to the states that were excluded from this study. Particularly, the results may be inapplicable to California, which has the longest history of medical marijuana legalization as well as the largest population of registered medical marijuana patients and the largest number of medical marijuana dispensaries. Third, although no statistical differences in hospitalization rates between states adopting and non-adopting medical marijuana policies were revealed before policy implementation, we cannot rule out policy endogeneity issues that may be caused by time-varying unobserved factors and were not captured by the two-way fixed effects models. In addition, we were not able to examine detailed policy provisions of medical marijuana legalization such as home cultivation and requirement of patient registry because of small sample size and lack of variations. We were not able to assess OPR-related policies that were adopted by a few states most recently, such as requirements of following OPR prescribing guidelines and mandatory checking prescription drug monitoring program data by providers. This limitation, however, is unlikely to influence the study findings significantly because these policies were not adopted until the very end of the study period or after the study period. Finally, the study findings do not apply to recreational marijuana legalization. In fact, the findings are likely to alter if marijuana for recreational purpose is indeed a gateway drug to OPR. Examinations on the most recent regulations of recreational marijuana are warranted. Laws and social norms around marijuana use are changing rapidly in the United States. Twenty-four states and Washington D.C. have legalized some form of medical marijuana, four additional states have decriminalized marijuana possession, and four states with medical marijuana policies recently voted to legalize retail marijuana.To inform policy efforts around marijuana, it is important to monitor the sociodemographic and psychosocial correlates of marijuana use. Nationally, young adults have the highest rates of past 30 day marijuana use, with 18.9% of 18–25 year olds using in 2013, compared to 7.1% of 12–17 year olds and 5.5% of adults 26 years old and older.In California marijuana use rates are even higher among young adults , and about 7% higher than cigarette use.However, rates of use may differ across race/ethnicity, sex, sexual orientation, socioeconomic status and region. National data show past 30 day marijuana use is highest among non-Hispanic Native Hawaiian/Pacific Islander young adults ages 18–25, followed by non-Hispanic American Indians , blacks , whites and Latinos .Men in this age range are also estimated to use marijuana at slightly higher rates , as are young adults with less than a high school education .However in longitudinal studies of adolescents, including those accounting for cannabis use disorders, non-Hispanic black adolescents and young adults and those identifying with two or more racial categories appear to be at greater risk.Furthermore, as local data may differ significantly from findings in national data sets, closer examination of sociodemographic associations with marijuana use in a diverse population of young adults may suggest unique targets for intervention. Young adulthood is a time of transition, in which people are navigating new roles and identities; it can also be a time of great stress.Past research has found that adolescents and young adults identify stress as a motive for using marijuana as they perceive it to be an effective coping method.Young adults who report using marijuana as a coping mechanism demonstrate poorer mental health outcomes and greater risk for marijuana dependence and other substance use, such as alcohol and tobacco,and some studies report Black and multiracial young people co-use marijuana with tobacco and alcohol more frequently.Psychological distress has also been shown to be related to use of marijuana in adults,but there is limited research on the relationship between psychological distress and marijuana use in young adults.At a population level distress is an especially useful measure as it quantifies sub-clinical incidence of mental illness and may provide additional insight as to how and why young adults use marijuana.Young adults’ who are transitioning in social roles may experience heightened feelings of loneliness, or a perceived deficit in the quality or quantity of their social relationships.Loneliness has been found to be positively related to alcohol and marijuana use, but not consistently.Conversely, perceived social support, or the idea that there are people in someone’s life who can provide emotional support and help with problems,might be associated with a lower probability of using marijuana. However at least one study among adolescents found social support to predict an increase in substance use while others have found inverse associations.