What was an illegal behavior not so long ago, became a legal behavior for some approximately twenty-two years ago, and is now a legal behavior for all in some states and countries. With that said, although for some individuals marijuana use may be purely medical or purely recreational, for many, medical and recreational use of marijuana overlaps . This study considers motives of marijuana use and associated mental health outcomes in a sample of young adults comprised of individuals who use marijuana exclusively for medical reasons, exclusively for recreational reasons or for both medical and recreational reasons, in a context with a longstanding history of legalized medical marijuana. It does so using an instrument that operationalizes marijuana motives of use to include both recreational as well as medical motives of use, which is a departure from motives of use questionnaires found thus far in the literature. Moreover, a better understanding of the association between motives of use and symptoms of depression and motives of use and symptoms of anxiety might allow one to detangle the association between marijuana use and diagnoses of depression and anxiety, and provides an avenue ripe for intervention. Finally, most of the work around marijuana use has not examined gender differences. But, as the gap in use prevalence between gender is decreasing and gender norms are changing, , it is imperative to better understand how marijuana use affects women differently than men. This work confirms that gender matters when examining the association between marijuana use and mental health outcomes,botanicare rolling benches and begins to lay the groundwork to better understand how motives of use may influence mental health outcomes differently for men and women.
Taken together, the findings presented in this dissertation contribute to the literature on motives of marijuana use and associated outcomes by demonstrating that there is a differential effect of motives of marijuana use on symptoms of mental health in young adults of Los Angeles who use marijuana for medical and/or recreational reasons. Whereas marijuana use driven by a coping motive is significantly associated with increases in symptoms of depression, symptoms of anxiety, and overall psychological distress, marijuana use driven by other motives does not appear to be directly associated with these mental health outcomes. However, when considering frequency of marijuana use, it becomes apparent that motives of pain, conformity and attention also influence mental health outcomes. Finally, associations for some of the motives, namely social anxiety, play out differently based on gender. These findings also have concrete implications for the development of interventions targeting marijuana use and mental health in young adults. Mainly, by targeting maladaptive coping practices. The findings also highlight the need for gender specific interventions as men and women engage in use differently, particularly in social settings. Given the exploratory nature of this work, these findings set forth an avenue of research on motives of marijuana use and mental health outcomes in young adults who use marijuana for medical and/or recreational reasons. First and foremost, although beyond the purposes of this dissertation, these associations should be compared between user groups , and looked at longitudinally. These findings should also be replicated using a larger, randomly selected sample.
To address some of the previously mentioned limitations, work should be pursued considering whether the strain of marijuana and concentration of cannabinoids versus tetrahydrocannabinol used play a role in the association between motives of marijuana use and symptoms of depression, symptoms of anxiety, and psychological distress. Finally, more work should be done to better understand and capture motives of marijuana use at time of use in order to eliminate the recall bias and get a better understanding of the associations between motives of marijuana use and mental health outcomes. As of January 2018, marijuana, in all its forms, is legal in California to over seventy five percent of its population. This comes after twenty-two years of medical marijuana being legal in California. Being only one of nine states to legalize all forms of marijuana, but being the more populous one, California has become the site of a large social experiment. The legalization of marijuana in all its forms, comes with little knowledge of what the social and health implications of what such an endeavor might be. In a context of legalized marijuana, there is an urgency to continue to detangle the associations between marijuana use and mental health in young adults to help ensure a successful transition to adulthood. Following medical marijuana legalization in over half states in the US and a few countries in Europe and America, in 2012, Colorado and Washington in the US first passed laws to legalize marijuana use by adults aged 21 or older. Since then, recreational marijuana legalization has been adopted in eight states and DC where one fifth of US population live . These state-wide laws emboldened other jurisdictions in the world to enable recreational marijuana market, with Uruguay and Canada passing country-level legalization in 2014 and 2017 , respectively. While intense debates are ongoing surrounding recreational marijuana legalization, little empirical evidence has been provided regarding its impacts on public health.
Primarily constrained by data availability, existing research typically conducted pre- and post-legalization evaluations on one or two states in the US controlling for contemporaneous trends in a limited number of comparison states . Study findings were mixed. Some states with recreational marijuana legalization saw an increase in marijuana use but no changes in motor vehicle crash fatality rates . The impacts of recreational marijuana legalization on other drugs remain unclear. Particularly, there have been considerable concerns about whether and how the opioid crisis may be influenced. Prescription opioid related harms are becoming a global problem, especially in the US . In the past 2 decades, the volume of opioid prescriptions quadrupled and opioid overdose deaths more than doubled . It is estimated that opioid misuse and overdose imposed an economic burden of $56 billion to the US each year . In 2017, opioid crisis was declared a “National Public Health Emergency” . There have been two hypotheses regarding the impacts of marijuana laws on opioid use. Marijuana is suggested to be effective in pain management and could be used medically by patients as substitutes for opioids. There were emerging population studies suggesting that medical marijuana patients reported substituting marijuana for opioids . The first hypothesis therefore suggested that liberalization of marijuana laws could reduce opioid use and related consequences if it increased marijuana use for medical purposes. In contrast, the competing hypothesis argued that marijuana, when used for non-medical purposes, could act as a gateway drug to opioids and result in increased opioid misuse and related outcomes. A recent study reported that non-medical marijuana use was associated with increased odds of prescription opioid misuse and opioid use disorder in a longitudinal, nationally representative sample in the US . Liberalization of marijuana laws may thus lead to a deterioration of opioid crisis if it encouraged non-medical use of marijuana. Both hypotheses regarding the impacts of marijuana laws on opioid use may be valid. The net effects of medical or recreational marijuana legalization could be either positive or negative, depending on which of the two hypotheses dominated in reality. Recent studies on medical marijuana legalization reported that substantial reductions in opioid-related deaths, misuse, drug prescriptions, traffic fatalities,commercial plant racks and inpatient stays were observed after medical marijuana was legalized . These findings appeared to support the first hypothesis, albeit indirectly, if marijuana use for medical purposes increased more than marijuana use for non-medical purposes as a result of medical marijuana legalization. Regarding recreational marijuana legalization, there has been continuous concern that the legalization may exacerbate opioid crisis if the legalization primarily impacted non-medical marijuana use. The empirical support is very limited. The only study focusing on recreational marijuana legalization indicated that the increasing trends in opioid-related deaths in Colorado were reversed following recreational marijuana legalization . However, data on a single state without comparison states lack generalizability and causal inferences. This study aimed to provide empirical evidence about the relationship between recreational marijuana legalization and prescription opioids. We focused on Medicaid enrollees in the US. Medicaid is a US health insurance program jointly funded by the federal government and states, primarily covering beneficiaries with low income and disabilities. Medicaid enrollees are a priority population for opioid control with a disproportionate burden of pain as well as a higher risk of opioid overdose and misuse . Using 2010–2017 state Medicaid drug prescription data, we were able to examine all the eight states and DC that have legalized recreational marijuana in the US. We explored the heterogeneity in policy responses by analyzing different drug schedules separately.
The primary outcome, prescription opioids received, were measured in three population adjusted variables: 1) number of opioid prescriptions, 2) total doses of opioid prescriptions ) , and 3) Medicaid spending on opioid prescriptions, per quarter per 100 Medicaid enrollees. Nominal spending was converted to 2017 constant US dollars using consumer price index. The number of Medicaid enrollees by state and year was obtained from annual Medicaid Managed Care Enrollment Reports . Prescription opioids were identified by linking the National Drug Code numbers in Medicaid State Drug Utilization Data to drug information in the Approved Drug Products with Therapeutic Equivalence Evaluations published by the US Food and Drug Administration . Because we were primarily interested in prescription opioids potentially substitutable by marijuana, we followed previous studies to exclude buprenorphine drugs typically used to treat opioid use disorder and included buprenorphine drugs commonly used in pain management . All methadone drugs were included because they were generally prescribed for pain management in outpatient settings that our data source captured. Schedule II and Schedule III opioids were categorized separately to reflect their differences in drug misuse and overdose potential. According to the most recent classifications by the Drug Enforcement Agency , Hydrocodone-combination drugs such as Vicodin and Lortab were classified as Schedule II drugs. The types of prescription opioids included in our analysis were listed in Table 1 by drug schedule. Following previous research , the primary policy variable was the implementation of statewide recreational marijuana legalization identified by law implementation dates. During the study period, eight states and DC implemented recreational marijuana legalization . Because state-level heterogeneity in the duration of legalization may have differential impacts on prescription opioids, three dichotomous policy variables were created to indicate recreational marijuana legalization taking effect at different time points : 4th quarter of 2012 , around 2nd quarter of 2015 , or around 4th quarter of 2016 . We also controlled for state-level time-varying covariates in the regressions, including a dichotomous variable indicating statewide medical marijuana legalization in effect, a dichotomous variable indicating statewide prescription drug monitoring program in effect, a dichotomous variable indicating statewide Medicaid expansion under the Affordable Care Act that provided insurance to all adults with income up to 138% of the US federal poverty level, a continuous variable for median household annual income adjusted to 2017 dollars with consumer price index, a continuous variable for annualized poverty rate, and a continuous variable for annualized unemployment rate .The analysis was conducted at state-quarter level. A difference-in-difference approach was used to assess the associations of legalizing recreational marijuana with the three log transformed continuous outcomes for Schedule II and Schedule III prescription opioids, separately. The coefficients in regression models can be interpreted as the average percentage change in prescription opioid outcomes in association with the implementation of recreational marijuana legalization. The underlying assumption in the difference-in-difference approach is parallel trends in treatment and comparison states in the absence of policy change . In our study, treatment states were eight states and DC that adopted recreational marijuana legalization in the study period. Before they adopted recreational marijuana legalization, they all had adopted medical marijuana legalization. Because medical marijuana legalization had significant impacts on trends in opioid-related outcomes including prescribing in Medicaid population , comparison states should have had medical marijuana legalization in effect to ensure their comparability with these treatment states prior to recreational marijuana legalization. We therefore made comparisons in two difference-in-difference models. Model A compared among eight states and DC themselves. Because they implemented recreational marijuana legalization at different time points, at a given time point, states that had not implemented legalization served as controls. Model B compared eight states and DC to six states that had implemented medical marijuana legalization as of January 1st, 2010 but had not implemented recreational marijuana legalization during the study period.