ReviewPrevalence, reasons, perceived effects, and correlates of medical marijuana use: A review
Introduction
Marijuana is the most widely used recreational drug in the U.S. The 2015 National Survey on Drug Use and Health (NSDUH) estimated that approximately 22.2 million Americans aged ≥12 years reported marijuana use (MU) in the past 30 days (Center for Behavioral Health Statistics and Quality (CBHSQ), 2016). MU, particularly long-term and heavy use, increases the likelihood of adverse health effects, such as motor vehicle accidents, chronic bronchitis and impaired respiratory function, psychotic symptoms, cognitive impairment, substance use disorder (SUD), and poor school performance (Hall, 2009, Hall and Degenhardt, 2009, Volkow et al., 2014). Of various recreational drugs, marijuana had the highest past-year prevalence of use disorder in the U.S. In 2015, past-year prevalence of MU disorder among Americans aged ≥12 years was 1.5%, which is higher than that of other drug use disorders, such as prescription opioid (0.8%), cocaine (0.3%), and heroin (0.2%) (CBHSQ, 2016). Considering the large population size of individuals who use marijuana recreationally and have MU disorder, problematic MU is an important public health issue that should be monitored to reduce its potential risks (Blanco et al., 2016, Wu et al., 2016).
In the U.S., marijuana is classified as a Schedule I drug under the Controlled Substances Act that has high potential for abuse and its medical use is prohibited (Hoffmann and Weber, 2010). Nevertheless, medical marijuana use (MMU), which refers to using marijuana as a medicine with a physician’s recommendation, is legal in many states. California became the first state to legalize the use of medical marijuana (MM) in 1996, and to date 28 states and District of Columbia passed MM laws—most recently, Florida, North Dakota, Arkansas, and Montana have approved a ballot measure that approves the use of MM. MM laws vary by states in terms of approved conditions but they typically include cancer, glaucoma, HIV/AIDS, cachexia, severe chronic pain, severe nausea, seizures, and severe muscle spasms (Hoffmann and Weber, 2010). While adults with a qualifying disease have legal access to MM, adolescents (under age 18) are only allowed to use MM under limited conditions with consent of a parent or caregiver. The landscape of MM laws is also rapidly changing globally. In Canada, the Marihuana Medical Access Regulations (MMAR) was enacted in 2001, which permitted the use of MM for severe illnesses upon approval by Health Canada. In 2014, the new Marihuana for Medical Purposes Regulations was enacted to replace the MMAR, enabling medical practitioners to prescribe MM regardless of patient’s medical conditions or failure of conventional treatments (Fitzcharles and Jamal, 2015). In Israel, individual patients can obtain a MM license after the Medical Cannabis Unit of the Ministry of Health approves a specialist’s recommendation (Sznitman and Lewis, 2015). In Australia, the New South Wales Government introduced the Terminal Illness Cannabis Scheme in 2014, which permitted the use of MM for adult with a terminal illness that meets the definition by the scheme (Martin and Bonomo, 2016). Recently, the Narcotic Drugs Amendment Bill of 2016 that legalizes the cultivation of marijuana for medical and scientific purposes went into effect on November 2016 (Parliament of Australia, 2016). In the U.K., Sativex® became the first licensed marijuana-based medicine for the treatment of Multiple Sclerosis (MS)-related spasticity in 2010 (Kmietowicz, 2010).
The global movement towards legalizing MM raises concern about its potential impact on public health. Joffe et al. (2004) suggested that legalization of MM may potentially reduce the risk perception related to MU and increase the availability of marijuana, which may contribute to MU by adolescents (Bachman et al., 1998, Swaim, 2003). During the MM commercialization period (2009–2011), adolescents (12–17 years) in Colorado showed significantly lower risk perception related to regular MU compared to the pre-MM commercialization period (2006–2008) than adolescents in non-medical marijuana states (NMMS) (Schuermeyer et al., 2014). A national survey of adults aged ≥18 years in the U.S. showed that residents in MM states had higher past-year prevalence of MU than residents in NMMS, although comparison was not made prior to and after implementation of MM laws in MM states and NMMS (Cerda et al., 2012).
To date, there is limited information that outlines patterns and correlates of MMU. Most of the available studies on MMU in the U.S. were conducted on samples of HIV/AIDS patients. A telephone survey of 180 HIV patients found that nearly 24% used marijuana for medical purposes in the past year, primarily due to nausea, weight loss, or diarrhea (52.8%) (Fairfield et al., 1998). An anonymous survey on 442 HIV/AIDS patients revealed that approximately 33% were those who used marijuana, mainly for improving relaxation/stress (79%), appetite/weight loss (67%), or nausea (66%) (Sidney, 2001). However, none of these studies addressed perceived effects of MM on symptoms, and there are very few studies on patients with other medical conditions. There is also little information about factors associated with MMU. Data from state-administered MM programs revealed that the majority of MM patients were male (75.4% in Arizona and 69% in Colorado) (Bowles, 2012). However, retrospective chart reviews of patients with authorized access to MM for chronic pain in Washington found that males and females were similar in terms of access to MM and duration of use (Aggarwal et al., 2009).
To date, no previous studies have systematically examined characteristics and patterns of MMU across age groups or medical conditions. To fill these research gaps, we conducted a literature review for both adolescents and adults in different countries to (1) assess MMU prevalence, (2) explore reasons and perceived effects of MMU, and (3) examine correlates of MMU.
Section snippets
Method
We conducted a literature search between August and September 2016 using databases PubMed, Google Scholar, Embase, CINAHL, and PsycINFO. The keywords “medical marijuana”, “medical cannabis”, or “medical cannabinoids” were combined with each of the following: “user” and “patients.” Peer-reviewed articles published in English between January 1996 and August 2016 and those that are clearly relevant to the scope of this review were considered for inclusion. In terms of quality assessment, studies
Results
Fig. 1 summarizes literature search process. Different combinations of keywords (“medical marijuana user”; “medical marijuana patients”; “medical cannabis user”; “medical cannabis patients”; “medical cannabinoids user” and “medical cannabinoids patients”) brought up the same article within search engine or with other search engines. The literature searches yielded 6502 potentially relevant records; after removing duplicate records. We excluded 6410 records that did not meet the inclusion
Discussion
This is the first study that reviewed prevalence, reasons for use, perceived effects, and correlates of MMU across age groups or medical conditions. The prevalence of self-reported MMU was 1.1% among a national sample of 12th graders in the U.S. The prevalence of MMU among adults aged ≥18 years who reported past-year marijuana use was 17%, according to the national survey data in the U.S. In the absence of national estimates in other countries, further research is needed to obtain global data
Role of funding source
This work was made possible by research support from the U.S. National Institutes of Health (UG1DA040317, R01MD007658, R01DA019623, PI, Li-Tzy Wu). The sponsoring agency had no further role in the study design and analysis, the writing of the report, or the decision to submit the paper for publication. The opinions expressed in this paper are solely those of the authors.
Contributors
Ji-Yeun Park contributed to the design and concept for this manuscript, conducted literature searches and review, and drafted the manuscripts. Li-Tzy Wu contributed to the design and concept for this manuscript, drafted the manuscripts, and supervised the work. All authors approved of the final manuscript before submission.
Conflict of interest
No conflict declared.
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