Has the Legalisation of Medical and Recreational Cannabis Use in the USA Affected the Prevalence of Cannabis Use and Cannabis Use Disorders ?
Janni Leung, Chui Ying Vivian Chiu, Daniel Stjepanović & Wayne Hall
Current Addiction Reports, 2018, 5, 403–417
Published online: 21 September 2018
# Springer Nature Switzerland AG 2018
Purpose of Review Since California legalised medical use of cannabis in 1996, 29 other US states have done so. Eight US states have legalised the retail sale of cannabis to adults over the age of 21 years since 2012. Critics of these policy changes have suggested that they will increase the prevalence of cannabis use and cannabis use disorders. This paper
(1) briefly describes the types of regulatory regimes for medical and recreational cannabis use in the USA,
(2) describes possible effects of these policies on cannabis use
and (3) assesses the impacts to date of the legalisation of medical and recreational cannabis use on the prevalence of cannabis use and cannabis use disorders in the US population.
We (1) describe the regulatory regimes for medical and recreational cannabis use in the USA,
(2) make predictions about their possible effects on the price and availability of cannabis,
(3) conduct a review to summarise studies of the effects of legalising medical cannabis use in the USA on rates of cannabis use and cannabis use disorders and
(4) assess early indications of the effects of legalising recreational cannabis use on cannabis use and cannabis use disorders.
Recent Findings : Liberal forms of medical cannabis regulation have probably reduced prices and increased the availability of cannabis. Analyses of survey data suggest that these changes have increased the prevalence and frequency of cannabis use among adults over the age of 21 years, but they have not to date increased rates of cannabis use among adolescents. Two series of epidemiological studies over a decade following the introduction of medical cannabis laws have produced inconsistent results on the effects of policy changes on the prevalence of cannabis use disorders in adults. One study found that the prevalence had increased; the other did not find an increase. An analysis of data on treatment seeking for cannabis use disorders showed an increase in states with medical cannabis laws in the number of adults seeking treatment who were not under legal coercion. There are major limitations with these studies, many of which have mistakenly assumed that all states with medical cannabis laws have similarly liberal policies.
Summary : It may be a decade or more before we can fully assess the effects of liberalisation of cannabis policies on cannabis use and cannabis use disorders in the USA. It is critical that the effects of these policy changes are evaluated to ensure that cannabis is regulated in ways that minimise the harmful effects of its regular use, especially among young people.
Keywords : Medical marijuana laws . Marijuana abuse . Cannabis use disorder . Health surveys . USA
Since the mid-1990s, a number of US states have passed citizen-initiated referenda to legalise the medical use of cannabis. This approach was first used in California in 1996 when voters passed Proposition 215 (by 56 to 44%) which allowed the medical use of cannabis for a broad set of indications that included nausea, weight loss, pain and muscle spasm and any “serious medical condition” for which cannabis may provide relief . Since then, 29 states have legalised medical use of cannabis in some form. US medical cannabis policy is subject to conflicting state and federal laws. Federally, cannabis is listed as a Schedule I drug under the Controlled Substances Act (CSA)  and hence classified as having a high potential for dependency and no accepted medical use. This makes the production, distribution and use of cannabis a federal offence. Proposition 215 in California in 1996 and subsequent legislation in many states that have enacted medical cannabis laws conflict with the CSA. These laws vary in which cannabis-containing products are permitted and whether they can be obtained by home cultivation or via dispensaries. In 16 states, only products that are low in the primary psychoactive cannabinoid, delta 9-tetrahydrocannabinol (THC) and high in cannabidiol (CBD), a non-psychoactive cannabinoid, are allowed for medical use. In some states, medical use is only allowed as a legal defence. Only four states and three territories do not allow any medical cannabis use (Idaho, South Dakota, Nebraska, Kansas, American Samoa, US Virgin Islands and Northern Mariana Islands). The conflict between federal and state policy on marijuana has resulted in a patchwork of state regulation [3–5]. For example, 29 jurisdictions (28 states and the District of Columbia) have legalised medical cannabis but only 18 mandate product safety testing before sale. Whilst the majority allow dispensaries, there is variation in their regulation. There are also large variations in the medical conditions that qualify for medical cannabis recommendations, although most jurisdictions include cancer, glaucoma and HIV/AIDS as eligible disorders. These policy variations made it difficult to map the possible influences of policy implementation on cannabis use and misuse, but they also provide opportunities to study the effects of a range of specific regulations on health outcomes.Medical marijuana policies across jurisdictions that have enacted comprehensive medical programs are highlighted in Text Box 1.