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Cannabis Legalization

Written by Dr. Ramon Martinez III
Published on April 8, 2022
Research Highlights

To date, 47 states in the U.S. have legalized the use of cannabis in some form for medical and/or non-medical purposes.

  • Cannabis contains two chemical compounds of therapeutic interest, and these have been shown to have a positive effect on pain, multiple sclerosis, and nausea. Two cannabis-derived drugs have been FDA-approved for epilepsy and chemotherapy-associated nausea.
  • Discrepancies exist in the legal status of cannabis sale, possession, and use between federal and state governments. This has led to variability in the enforcement of cannabis laws; more than half of states have decriminalized possession of small amounts of cannabis, and most allow a process to clear one’s criminal record.
  • Thirty-seven states have a legal medical cannabis program, and eighteen have also legalized cannabis for non-medical purposes.
    • Several of the states to legalize non-medical cannabis have collected tax revenues totaling over $100M annually.

Executive Summary

To date, 47 states in the U.S. have legalized the use of cannabis in some form for medical and/or non-medical purposes. While cannabis has shown strong evidence for medicinal use for several chronic diseases, it may also have a low potential for substance abuse. States that have since legalized cannabis for non-medical use have also seen significant tax revenue from sales. Article XIV Section 1 of the Missouri Constitution guarantees the right to medical cannabis access to patients. Twenty-three bills have been introduced by both major political parties in the 2022 Missouri legislative session that change current laws related to cannabis, including: the legal use of medical cannabis, how medical facilities operate, and the criminality of medical and non-medical cannabis use.


  • Given the status of cannabis as a Schedule I drug, access and research on its effects and therapeutic potential are limited, and more studies are needed to make firm conclusions.
  • Given that no state has had legal non-medical use for more than a decade, the full long-term effects of cannabis legalization have yet to be determined.

Research Background

Terminology and Pharmacology of Cannabis

Cannabis (often interchangeably used with “marijuana”) is a plant of the species Cannabis sativa or Cannabis indica, and contains over 540 chemical compounds of pharmacological interest.1 The two most abundant and well-known of these compounds (under the sub-class cannabinoids) are cannabidiol (CBD) and delta-9-tetrahydrocannabinol (THC).2

Hemp (a type of cannabis with less than 0.3% of the psychoactive compound THC) was removed from Schedule I of the federal Controlled Substances Act (CSA) under the Agriculture Improvement Act of 2018, given the non-psychoactive nature of CBD and agricultural uses of hemp.2 All but two states (ID and MS) allow hemp for agricultural and industrial production.3

Both CBD and THC bind to receptors in the body (known as endocannabinoid receptors), through either inhalation or oral ingestion, and rapidly distribute to the brain, fat tissues, and other organs. While THC is known as a psychoactive chemical for its ability to temporarily alter one’s perception, CBD has no psychoactive effects.4

Research Limitations on Cannabis

In 1970, the Controlled Substances Act was signed into law, categorizing cannabis as a Schedule I substance with no acceptable medical use and having a high potential for abuse.5 Given this historical classification, research institutions have faced restrictions on obtaining cannabis for investigational purposes, including the potential medical applications, effects on behavior, and treatment efficacies.6 This has limited the quantity of available U.S.-generated literature by excluding federal funding and limiting access to cannabis grown in the National Institutes for Drug Abuse (NIDA) program.

In 2016 the U.S. Drug Enforcement Administration (DEA) made a policy change to allow additional entities to register, grow, and distribute cannabis for FDA-approved research purposes.6 For drug development purposes, any low-THC hemp-derived products go through a relatively similar FDA approval process as other drugs, while higher THC products must go through a DEA-supervised FDA approval.2

Medical Cannabis

To date, the U.S. Food and Drug Administration (FDA) has not approved the use of the cannabis plant for medical use (especially if containing THC), but 37 states and 4 U.S. territories have legalized the use of cannabis products for medical use. In addition, several purified products containing cannabinoids have been approved by the FDA, including Epidiolex (purified CBD, used to treat two severe forms of epilepsy), and Marinol, Syndros, and Cesamet (synthetic THCs, used to treat cancer or HIV-associated nausea, vomiting, and appetite loss).1

Given the recency of the DEA expansion of authorization of cannabis research (done in 2016), more research may be needed to determine its potential positive and negative effects.5 While past research on the efficacy of cannabis use or cannabinoids has been limited, there is substantial scientific evidence that these products have a positive effect on relieving chronic pain, the symptoms of multiple sclerosis, and chemotherapy-induced nausea and vomiting.6 There is also moderate evidence suggesting that sleep disturbances can be reduced, and limited evidence in regaining appetite, improving Tourette’s symptoms, anxiety, the effects of traumatic brain injury, and post-traumatic stress disorder (PTSD) symptoms. Evidence has been inconclusive in treating dementia, glaucoma, depression, irritable bowel syndrome, glioma, paralysis, Hungtington’s and Parkinson’s disease, anorexia, schizophrenia, and treating substance abuse of other drugs (e.g., opioids).6

Health Effects of Cannabis

Cannabis products can have debilitating effects depending on the duration, amount, use of other drugs, and underlying medical conditions of the user. While roughly 193 million users self-report using cannabis worldwide, cannabis use disorder (CUD; which occurs when the desire to achieve the ‘high’ from THC leads to dependence), affects nearly 10% of users (a percentage notably similar to alcohol use disorder).7,8 Use of cannabis before the age of 16 may also increase the risk for developing CUD, and is more likely if one has a mood disorder, anxiety, or PTSD.7 Further, like smoking tobacco, cannabis smoke can be harmful to the lungs by delivering some of the same cancer-causing toxins as cigarettes, and can cause issues with memory and recall in heavy users.9 Contaminants from vape products or unregulated cannabis products can also be harmful. For example, vape products have been linked to serious lung injuries, and unregulated cannabis products have been found to have microorganisms and pesticides that can cause illness.1 While the evidence is limited, cannabis use may also increase the risk of using other drugs, but these findings were largely dependent on one’s sociodemographic characteristics, other psychiatric disorders, and environmental pressures for substance abuse.10

Federal and State Drug Enforcement and Criminalization of Cannabis

While the status of cannabis (in particular with high THC levels) as a Schedule I drug at the federal level limits the legal use and prescription of THC products, many states have moved to institute medical cannabis programs or completely legalized non-medical use. This legal discrepancy has been interpreted differently over the last several Presidential administrations, with enforcement of federal criminal laws left largely to the discretion of the U.S. Department of Justice (which has prioritized other crimes), or subject to executive recommendations not to prosecute.11 The current administration has announced made any formal stance on enforcement of federal cannabis laws. States with established medical cannabis programs and registries also may provide protections from arrests for posession.11

Twenty-seven states (including NE, IL, and MO) and Washington, D.C. have decriminalized possession of small amounts of cannabis, while a further 16 states (including, KS, OK, & IL) have modified the criminal penalties for cannabis convictions.12 Moreover, 41 states (including Missouri and neighboring states) and Washington, D.C. have a process for clearing one’s criminal record for past criminal charges. This can help lift restrictions on other life activities such as professional licensing, voting, employment, education, housing, and receiving government support.13,14

Effects of Criminalization on Minority Populations

Nationwide, over seven million arrests for cannabis possession were made between the period of 2001–2010, comprising more than half of all drug-related arrests. Data indicates that there are clear racial disparities in these arrests, with Black Americans 3.73 times more likely to be arrested for cannabis possession, despite similar rates of cannabis use among both Black and White Americans. Roughly $3.6 billion in taxes were spent in 2010 to enforce U.S. possession laws. Missouri was also consistently in the top 15 states for highest arrest rates for cannabis possession from 2001-2010; during this period Black individuals were 2.5 as likely overall to be arrested for possession statewide as their White counterparts, and 18.4 times as likely to be arrested for possession in St. Louis City.15

State-Level Legislation

As of February 2022, 37 states and 4 U.S. territories have legalized the use of cannabis products for medical use (Figure 1).11 Further, 18 states, 2 territories, and Washington, D.C. have enacted legislation that legalizes and regulates the use of cannabis for non-medical/recreational purposes. Eleven states have legalized the use of high CBD/low THC hemp-derived compounds for medical purposes.11


Figure 1: Map of states where medical and non-medical cannabis use has been legalized. States with legalization of cannabis for all purposes are in dark green, states with medical-only purposes are in green, states with legalized hemp (low THC product) use are in light green. All but 3 states have legalized cannabis use in some form. Map reproduced from the National Conference of State Legislatures.11

Missouri Legislation

Article XIV Section 1 of the Missouri Constitution guarantees the right to medical cannabis access to patients being treated for cancer, epilepsy, glaucoma, migraines, debilitating psychiatric disorders, HIV, terminal illnesses, chronic conditions that could lead to dependence on other drugs, and other conditions under the professional judgment of a physician. Patients must be registered with the Department of Health and Senior Services for purchasing or personal cannabis cultivation.16 Further, while medical cannabis and low-THC hemp products are legal to use, both a federal and state-level determination on the regulation of products with Delta-8 or Delta-10 THC (other cannabinoids found in cannabis) has yet to be established.17

In the 2022 Missouri legislative session, 23 bills have been introduced by both major political parties regarding the legal use of medical cannabis, how facilities run, the criminality of cannabis use, or directly legalizing the use for all adults 21 and over (Table 1).

Bill Category and Descriptions

Bill No.

Medical cannabis facilities: institutionalizes legal procedures for operation, clarifies labeling for CBD, provides tax incentives, or reduces administrative burdens on operation

(HB 1523, 1658, 1726, 1736, 1851, 1895, 1901, 2540 & 2667, HJR 142, SB 807, 939)

Changes the legal consequences for users: modify the offenses for cannabis possession, allow for expungement of records for cannabis possession, prohibit property searches for suspected use, or prohibits court determinations when used medically


(HB 1537, 1659, 1867, 2440, 2469, SB 793, 794)

page5image3962273792 page5image3962274096 page5image3962274400 page5image3962274704 page5image3962275072

Full legalization for Adults over 21: Proposes a constitutional amendment ballot vote, removal from the state list of controlled substances, or allows for purchases or personal cultivation


(HJR 83, 2704, 2733, 2869)

page5image3962302336 page5image3962302864 page5image3962303168

Table 1: Bills changing the legal status of medical and non-medical cannabis use and facility operations.

Post-Legalization Effects

A study in 2021 determined that while rates of cannabis use have increased since several states (including AK, CA, CO, MA, ME, NV, OR, WA) legalized non-medical use for adults, rates had already been increasing in the 5 years prior to legalization, and highlight a more general trend toward increased use nationwide.18

Legalization has shown no effect on road fatalities, and may act as a less risky pain relief alternative to opioid overdoses. Further, cannabis legalization has had no correlation with lowering other illicit drug abuses, and has had no effect on suicide rates or crime.18

Economically, the legal cannabis industry accounted for $12.2 billion in the US and $14.9 billion worldwide in 2019.19 Cannabis legalization, while only providing modest increases in employment numbers in legalized states, had a significant impact on state tax revenue, in particular for recreational use. States that have since legalized use collecting between $10-135 million in revenue each month since legalization with no clear increase on criminal justice expenditures.18 Further, a survey of high school seniors determined that legalization laws have had very little impact on adolescent cannabis use, other substance use, alcohol consumption, youth health outcomes, criminal behavior, and traffic accidents.20

Driving Under the Influence (DUIs)

One area of interest is whether non-medical cannabis use is correlated with an increased DUI rate. A 2015 National Highway Traffic Safety Administration noted that nationwide (whether in legal or non-legal states) there was an 8-12% increase in cannabis-positive weekend nighttime drivers between 2007 and 2014.21 Further, a 2017 Colorado study determined that DUIs where cannabis was noted as an impairing substance was 16% higher than a comparable period two years earlier.22

There are different types of tests used to determine whether cannabis is an impairing factor for driving. While tests for alcohol intoxication (such as a breathalyzer) can reliably infer impairment on-site, tests for cannabis intoxication (such as blood tests) are ultra-sensitive and may detect the presence of chemical compounds (such as THC) days or even weeks after use, long after the impairment period.21 Oral fluid tests are a newer technology that can be used to detect recent cannabis use, but it is difficult to draw conclusions about their field efficacy and use given that on-site tests for cannabis-DUIs do not meet current analytics standards and have only been used in small pilot studies in only three states (AL, CO, and MI).23,24 As of 2021, several states have updated legislation to infer intoxication if THC levels are detectable above a legal limit of 5ng/ml of blood (such as CO, IL, MT, NV, OH, and WA).23

Notably, of driving fatalities in Colorado where cannabis was detected, 42% were also attributable to alcohol use, making cannabis-exclusive impairment hard to discern. This may point to a general increasing trend in driving under the influence of drugs whether in legal or non-legal states.22,23 Given the short time states have legally allowed non-medical cannabis use (first state in 2012), long-term trends are still difficult to determine.


  1. Cannabis (Marijuana) and Cannabinoids: What You Need To Know, <https://www.nccih.nih.gov/health/cannabis-marijuana-and-cannabinoids-what-you-need-to-k now>
  2. FDA and Cannabis: Research and Drug Approval Process, (2020). <https://www.fda.gov/news-events/public-health-focus/fda-and-cannabis-research-and-drug- approval-process>.
  3. State Industrial Hemp Statutes, (2020). <https://www.ncsl.org/research/agriculture-and-rural-development/state-industrial-hemp-stat utes.aspx#:~:text=The%202018%20Farm%20Bill%20changed,plant%20species%20Cannabis%20sa tiva%20L.> .
  4. Chayasirisobhon, S. (2020). Mechanisms of Action and Pharmacokinetics of Cannabis. Perm J 25, 1-3, doi:10.7812/tpp/19.200.
  1. About Cannabis Policy, <https://alcoholpolicy.niaaa.nih.gov/about-cannabis-policy#:~:text=In%20the%20Controlled%2 0Substances%20Act,the%20highest%20potential%20for%20abuse.>
  2. National Academies of Sciences, E. & Medicine. (2017). The health effects of cannabis and cannabinoids: the current state of evidence and recommendations for research.
  3. Connor, J. P. et al. (2021). Cannabis use and cannabis use disorder. Nat Rev Dis Primers 7, 16-16, doi:10.1038/s41572-021-00247-4.
  4. Grant, B. F. et al. (2017). Prevalence of 12-Month Alcohol Use, High-Risk Drinking, and DSM-IV Alcohol Use Disorder in the United States, 2001-2002 to 2012-2013: Results From the National Epidemiologic Survey on Alcohol and Related Conditions. JAMA Psychiatry 74, 911-923, doi:10.1001/jamapsychiatry.2017.2161.
  5. Health Effects of Marijuana, (2021).<https://www.cdc.gov/marijuana/health-effects/index.html>.
  6. RiskofUsingOtherDrugs, <https://www.cdc.gov/marijuana/health-effects/risk-of-other-drugs.html#:~:text=Researchers %20disagree%20on%20whether%20marijuana,drugs%2C%20like%20cocaine%20or%20heroin.&te xt=However%2C%20there%20is%20limited%20evidence,risk%20of%20using%20other%20drugs. >
  7. State Medical Cannabis Laws, (2022). <https://www.ncsl.org/research/health/state-medical-marijuana-laws.aspx>.
  8. Hartman,M.CannabisOverview,(2021). <https://www.ncsl.org/research/civil-and-criminal-justice/marijuana-overview.aspx> .
  9. Hartman,M.ClearingCriminalRecordsforCannabisOffenses,(2020). <https://www.ncsl.org/research/civil-and-criminal-justice/clearing-criminal-records-for-cannab is-offenses.aspx> .
  10. Collateral Consequences: The Crossroads of Punishment, Redemption, and the Effects on Communities, (2019). <https://www.usccr.gov/files/pubs/2019/06-13-Collateral-Consequences.pdf> .
  11. The War on Marijuana in Black and White,(2013). <https://www.aclu.org/sites/default/files/field_document/1114413-mj-report-rfs-rel1.pdf> .
  12. Medical Marijuana in Missouri,<https://health.mo.gov/safety/medical-marijuana/pdf/205.pdf>
  13. MedicalMarijuana-GeneralFAQs, <https://health.mo.gov/safety/medical-marijuana/faqs-general.php>
  14. Dills, A. K., Goffard, S., Miron, J. & Partin, E. (2021). The effect of state marijuana legalizations: 2021 update. Cato Institute, Policy Analysis.
  15. Hollenbeck,B.&Uetake,K.(2021).Taxation and market power in the legal marijuana industry. The RAND Journal of Economics 52, 559-595.
  16. Dills,A.K.,Goffard,S.&Miron,J.(2017).The effects of marijuana liberalizations: Evidence from monitoring the future. (National Bureau of Economic Research, 2017).
  17. Berning,A.,Compton,R.&Wochinger,K.(2015).Results of the 2013–2014 National Roadside Survey of Alcohol and Drug Use by Drivers. (National Highway Traffic Safety Administration, 2015).
  18. Ghosh,T.S.etal.(2017).Lessons learned after three years of legalized, recreational marijuana: The Colorado experience. Prev Med 104, 4-6, doi:10.1016/j.ypmed.2017.02.021.
  19. Drugged Driving | Marijuana-Impaired Driving, (2021). <https://www.ncsl.org/research/transportation/drugged-driving-overview.aspx>
  20. Dobri, S. C. D., Moslehi, A. H. & Davies, T. C. (2019). Are oral fluid testing devices effective for the roadside detection of recent cannabis use? A systematic review. Public Health 171, 57-65, doi:10.1016/j.puhe.2019.03.006.
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