Elsevier

Drug and Alcohol Dependence

Volume 169, 1 December 2016, Pages 26-32
Drug and Alcohol Dependence

Full length article
State-level medical marijuana laws, marijuana use and perceived availability of marijuana among the general U.S. population

https://doi.org/10.1016/j.drugalcdep.2016.10.004Get rights and content

Highlights

  • Marijuana use increased in adults 26+ after enactment of medical marijuana laws (MML).

  • Among adults 26+ perceived availability of marijuana increased after MML were enacted.

  • Perceived availability was associated with marijuana use.

Abstract

Background

Little is known on how perceived availability of marijuana is associated with medical marijuana laws. We examined the relationship between medical marijuana laws (MML) and the prevalence of past-month marijuana use, with perceived availability of marijuana.

Methods

Data were from respondents included in the National Survey of Drug Use and Health restricted use data portal 2004–2013. Multilevel logistic regression of individual-level data was used to test differences between MML and non-MML states and changes in prevalence of past-month marijuana use and perceived availability from before to after passage of MML among adolescents, young adults and older adults controlling for demographics.

Results

Among adults 26+, past-month prevalence of marijuana use increased from 5.87% to 7.15% after MML passage (Adjusted Odds Ratio (AOR): 1.24 [1.16–1.31]), but no change in prevalence of use was found for 12–17 or 18–25 year-olds. Perceived availability of marijuana increased after MML was enacted among those 26+ but not in younger groups. Among all age groups, prevalence of marijuana use and perception of it being easily available was higher in states that would eventually pass MML by 2013 compared to those that had not. Perceived availability was significantly associated with increased risk of past-month marijuana use in all age groups.

Conclusion

Evidence suggests perceived availability as a driver of change in use of marijuana due to MML. To date, this has only occurred in adults 26+ and different scenarios that could explain this change need to be further explored.

Introduction

A major concern with the enactment of medical marijuana laws (MML) is that this type of legislation could potentially increase marijuana use in adolescents and adult populations (Cerdá et al., 2012). A potential pathway in which this may occur involves the recognition that MML have been passed and could be increasing the availability of marijuana in the U.S. Increases in availability of marijuana on its own may normalize both medical and non-medical marijuana use and reduce harm-related risk perceptions of marijuana use, which could result in changes in marijuana use (Bestrashniy and Winters, 2015, Palamar et al., 2014, Piontek et al., 2013). Some studies suggest that individuals’ perception of availability of an illegal drug can also influence drug use patterns (Ennett et al., 1997, Hanson et al., 2003). Increased availability of marijuana may generate changes in the supply market resulting in drops in price of marijuana, which in turn may influence the overall use of it in the population (Pacula et al., 2015). However, although it is believed to have increased over the last decade, estimates of yearly availability of marijuana in the U.S. either produced domestically or internationally are unknown (NDIC, 2010).

Recent evidence suggests that, while not all MML states have enforced patient registration, the number of patients registered in medical marijuana programs across states have increased over time in MML states, particularly after 2009 when there were substantial changes in federal prosecution laws regarding marijuana cultivation, distribution and possession (Fairman, 2016). In addition, registration fees vary widely across MML states (Williams, 2016) Also, research has reported that home cultivation and the presence of dispensaries in MML states have resulted in diversion of marijuana to individuals (Nussbaum et al., 2015, RMHIDTA, 2014, Wirfs-Brock et al., 2010), including youth (Salomonsen-Sautel et al., 2012, Thurstone et al., 2011), who then use it for non-medical purposes. Non-MML states may also be affected by the diversion of marijuana illegally moving from MML states to non-MML states (RMHIDTA, 2014). All these factors could have potentially increased the overall availability of marijuana across states; however, it is also possible that other factors, such as reductions in illegal marijuana coming from out of the U.S. (UNODC, 2015; i.e., there has been a decrease in seizures of illegal marijuana entering in the U.S. since 2009), could have balanced out the MML effects. As such, measuring the availability of marijuana across states in a specific year is challenging given the limitations to quantify the amount of available of marijuana in illegal street-markets and sold through the Internet, and the surplus of medical marijuana from home cultivation productions and legal dispensaries that is diverted to the public (Pacula et al., 2015, Smart, 2015). Smart (2015) has reported that growth in the legal medical marijuana market is associated with increases in recreational use among adolescent and adults. In this regard, measures of overall perception of availability could be an intermediate step between changes in actual availability and marijuana use, and could provide some insight on how availability is associated with marijuana use in states enacting MML.

To date, some studies have examined if perceived availability is associated with the prevalence of marijuana use (Bonn-Miller et al., 2014, Friese and Grube, 2013, Khatapoush and Hallfors, 2004, Miech et al., 2015, Salomonsen-Sautel et al., 2012, Schuermeyer et al., 2014, Smart, 2015). However, these studies are restricted populations of only medical users (Bonn-Miller et al., 2014), had limited to analyses in a single state (Bonn-Miller et al., 2014, Friese and Grube, 2013, Khatapoush and Hallfors, 2004), only explored perceived availability as an outcome of marijuana policies in the mid to late 1990s (Khatapoush and Hallfors, 2004), or mostly have focused on youth populations (Friese and Grube, 2013, Kokkevi et al., 2000, Miech et al., 2015, Piontek et al., 2013, Steppan et al., 2013, ter Bogt et al., 2006, ter Bogt et al., 2014). Data from the Monitoring the Future (MTF) study has shown that perceived availability among 12th graders has been stable since 1975 (80–90% report it is fairly easy to obtain marijuana), has always been higher in 12th graders as compared to 8th and 10th graders (37% of the 8th graders and 66% of the 10th graders reported it was fairly easy to obtain in 2014) and is currently at a historic low among this population (Miech et al., 2015). In addition, another study with MTF data (Shi, 2016) shows that 8th grade students from schools located close to medical marijuana dispensaries (short traveling distance, <5 miles) were more likely to have recently use marijuana compared to those from schools located farther apart from dispensaries (>25 miles). To date, there is little information on how perceived availability is associated with marijuana use among adults, those comprising the majority of licensed medical marijuana users (Anderson et al., 2015a), as well as the total overall users of marijuana. To our knowledge, no study has investigated whether perceived availability of marijuana is associated with the relationship between state medical marijuana laws and the state-level differences in prevalence of marijuana use in the U.S. general population. Also, although evidence suggests that MML are associated with increases in marijuana use among those ages 21 and older (Wen et al., 2015), is not clear if all adults (age sub-groups) have been influenced in the same way and whether perceived availability could be linked to increase use across all age sub-groups. Our study aims to address these gaps.

In addition, because MML are intended to target mostly the population of older patients with illnesses that can be potentially be treated with medical marijuana (e.g., chronic pain or cancer; Fairman, 2016), it is likely that MML laws affect different age groups differently, and through different modes of access (Hasin et al., 2015). Understanding the potential externalities of MML in different age groups, such as potential increases in recreational marijuana use among adolescents, young adults and older adults, would improve our understanding of the effects of marijuana policies and provide information about the types of public health responses that should accompany major policy changes related to marijuana.

Therefore, the aims of this paper are: 1) To examine the relationship between state-level MML and past-month marijuana use among adolescents, young adults and older adults in the US household population from 2004 to 2013; 2) To examine whether state-level MML is associated with perceptions of marijuana availability; and 3) To assess whether perceptions of marijuana availability are associated with past-month marijuana use among adolescents, young adults and older adults.

Section snippets

Data

Observationscame from ten years of annual cross-sectional survey data from the National Survey of Drug Use and Health (NSDUH) restricted use data portal 2004–2013 (CBHSQ, 2015). Since 2004 (first year in which restricted-access NSDUH data are made available), data on more than 17,500 youth (12–17 years-old), 17,500 young adults (18–25 years-old) and 18,800 adults older than 26 years old have been collected yearly in the NSDUH. The NSDUH was designed to produce estimates of drug and alcohol use

Results

Past-month prevalence of marijuana use and perceived availability (marijuana is fairly or very easy to obtain) during the 2004–2013 period was higher among individuals aged 18–25 compared with those ages 12–17 and those 26 or older regardless of MML state status (Fig. 1A,B).

States that ever passed MML had higher prevalence of past-month marijuana use in each age group before passing MML compared to states that never passed these laws (Table 1A and Fig. 1A). However, among 12–17 and 18–25

Discussion

This study shows an increase in the prevalence of past-month marijuana use from the before to the after MML period in adults 26–39, 40–64, and 65+ between 2004 and 2013. There was no increase in the prevalence of past-month in adolescent or young adult comparing the before and after MML periods in states that implemented MML. These findings are consistent with findings from prior studies (Anderson et al., 2015b, Choo et al., 2014, Harper et al., 2012, Hasin et al., 2015, Lynne-Landsman et al.,

Role of funding

This study was partially funded by the National Institutes of Health, National Institute on Drug Abuse (NIH-NIDA) [grants R01 DA037866 (PI: Martins), R01 DA034244 (PI: Hasin), K01DA030449 (PI: Cerdá), and T32 DA031099 (PI: Hasin)]; National Institutes of Health, National Institute of Alcohol and Alcoholism (NIH-NIAAA) [grant K01AA021511 (PI: Keyes)]. Dr. Santaella is funded by the J. William Fulbright and the Colciencias doctoral scholarships. Dr. Hasin is also funded by the New York State

Contributors

Dr. Martins, Dr. Mauro and Mr. Santaella design and conceptualized the study. Dr. Mauro and Mr. Santaella analyzed the data under Dr. Martins’ and Wall’ supervision and also drafted sections of the manuscript. Dr. Martins wrote the first full draft of the manuscript. All other authors critically reviewed and edited the manuscript and approved the final version for submission.

Conflict of interest

The authors have no conflict of interest to declare.

Acknowledgments

The authors would like to thank the National Survey on Drug Use and Health NSDUH study respondents and Substance Abuse and Mental Health Service Administration (SAMHSA) for access to the restricted-use NSDUH files.

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