Policies that legalize marijuana for medical purposes remove civil or criminal penalties and permit the sale and use of medical marijuana products for eligible patients (Pacula 2017*, Guttmannova 2016*). Marijuana use is illegal in the United States at the federal level. Some states allow medical marijuana use for eligible patients; requirements and restrictions regarding patient authorization and registration, caregiver role and registration, medical conditions, home cultivation, and dispensary permission vary by state (NCSL-MMLs).
Expected Beneficial Outcomes (Rated)
Improved health outcomes
Reduced substance abuse
Reduced alcohol-related harms
Other Potential Beneficial Outcomes
Reduced illegal drug use
Evidence of Effectiveness
There is mixed evidence about the health benefits and risks of legalizing marijuana for medical use.
Medical marijuana has been shown to reduce spasticity and chronic pain including neuropathic pain (NASEM 2017, Whiting 2015*, Hill 2015*, Koppel 2014, Cinti 2009*), and treat nausea and vomiting for patients (NASEM 2017). Studies of states with medical marijuana laws (MMLs) suggest legalization can reduce opioid overdose deaths (Bachhuber 2014*) and opioid abuse-related hospitalization (Shi 2017*). MMLs that permit dispensaries also appear to be associated with decreases in opioid addiction and overdose deaths (NBER-Powell 2015).
However, legalizing marijuana for medical use can increase marijuana use and dependence among adults (Pacula 2017*, Maxwell 2016, Pacula 2015), especially high-risk users (e.g., arrestees, heavy users, and multiple substance users) (Pacula 2017*). MMLs are associated with increased risk of unintentional toxic ingestions of medical marijuana products among children (Wang 2013a*, RAND-Pacula 2017) and may increase youth initiation of marijuana use (Wen 2015*). Additional evidence is needed to confirm effects on youth use overall (Pacula 2017*). Youth marijuana use may harm academic and employment outcomes, and social relationships (NASEM 2017).
Some studies suggest that MMLs may increase both marijuana and alcohol use. However, other studies suggest that MMLs may increase marijuana use but decrease alcohol use (Guttmannova 2016*).
Smoking marijuana may lead to respiratory problems, heart attacks, and cancers (NASEM 2017, Leung 2011). Marijuana use may also increase the risk of psychotic and schizophrenic symptoms and may worsen schizophrenia, especially in genetically susceptible individuals and youth (Caulkins 2012*, Bostwick 2012). Marijuana initiation before adulthood may increase the likelihood of dependence and related harms (Caulkins 2012*, Wilsey 2008*, Bostwick 2012); initiation over the age of 25 rarely results in dependence (Bostwick 2012).
Impact on Disparities
As of August 2019, medical marijuana is legal in 33 states and Washington DC; these states also have comprehensive medical marijuana and cannabis programs. Thirteen states allow limited use of low tetrahydrocannabinols (known as THC), high cannabidiol (CBD) products for specific medical conditions. Idaho and Kansas ban marijuana use (NCSL-MMLs, MPP).
As of October 2019, 11 states and Washington DC allow residents to use marijuana for recreational use (NCSL-Marijuana).
Citations - Evidence
* Journal subscription may be required for access.
NASEM 2017 - National Academies of Sciences, Engineering, and Medicine (NASEM). The health effects of cannabis and cannabinoids: The current state of evidence and recommendations for research. Washington, DC: The National Academies Press; 2017.
Whiting 2015* - Whiting PF, Wolff RF, Deshpande S, et al. Cannabinoids for medical use: A systematic review and meta-analysis. JAMA. 2015;313(24):2456-2473.
Hill 2015* - Hill KP. Medical marijuana for treatment of chronic pain and other medical and psychiatric problems: A clinical review. JAMA. 2015;313(24):2474-2483.
Koppel 2014 - Koppel BS, Brust JCM, Fife T, et al. Systematic review: Efficacy and safety of medical marijuana in selected neurologic disorders: Report of the Guideline Development Subcommittee of the American Academy of Neurology. Neurology. 2014;82(17):1556-1563.
Cinti 2009* - Cinti S. Medical marijuana in HIV-positive patients: What do we know? Journal of the International Association Providers of AIDS Care. 2009;8(6):342-6.
Bachhuber 2014* - Bachhuber MA, Saloner B, Cunningham CO, Barry CL. Medical cannabis laws and opioid analgesic overdose mortality in the United States, 1999-2010. JAMA Internal Medicine. 2014;174(10):1668-1673.
Shi 2017* - Shi Y. Medical marijuana policies and hospitalizations related to marijuana and opioid pain reliever. Drug and Alcohol Dependence. 2017;173:144-150.
NBER-Powell 2015 - Powell D, Pacula RL, Jacobson M. Do Medical Marijuana Laws Reduce Addictions and Deaths Related to Pain Killers? National Bureau of Economic Research (NBER). 2015: Working Paper 21345.
Pacula 2017* - Pacula RL, Smart R. Medical marijuana and marijuana legalization. Annual Review of Clinical Psychology. 2017;13(1):397-419.
Maxwell 2016 - Maxwell JC, Mendelson B. What do we know about the impact of the laws related to marijuana? Journal of Addiction Medicine. 2016;10(1):3-12.
Pacula 2015 - Pacula RL, Powell D, Heaton P, Sevigny EL. Assessing the effects of medical marijuana laws on marijuana use: The devil is in the details. Journal of Policy Analysis and Management. 2015;34(1):7-31.
Wang 2013a* - Wang GS, Roosevelt G, Heard K. Pediatric marijuana exposures in a medical marijuana state. JAMA Pediatrics. 2013;167(7):630-633.
RAND-Pacula 2017 - Pacula RL. Regulating medical marijuana markets: Insights from scientific evaluations of state experiments. Santa Monica, CA: RAND Corporation; 2017.
Wen 2015* - Wen H, Hockenberry JM, Cummings JR. The effect of medical marijuana laws on adolescent and adult use of marijuana, alcohol, and other substances. Journal of Health Economics. 2015;42:64-80.
Guttmannova 2016* - Guttmannova K, Lee CM, Kilmer JR, et al. Impacts of changing marijuana policies on alcohol use in the United States. Alcoholism: Clinical & Experimental Research. 2016;40(1):33-46.
Leung 2011 - Leung L. Cannabis and its derivatives: Review of medical use. Journal of the American Board of Family Medicine. 2011;24(4):452-62.
Caulkins 2012* - Caulkins JP, Hawken A, Kilmer B, Kleiman MAR. Marijuana legalization: What everyone needs to know. New York: Oxford University Press; 2012.
Bostwick 2012 - Bostwick JM. Blurred boundaries: The therapeutics and politics of medical marijuana. Mayo Clinic Proceedings. 2012;87(2):172-86.
Wilsey 2008* - Wilsey B, Marcotte T, Tsodikov A, et al. A randomized, placebo-controlled, crossover trial of cannabis cigarettes in neuropathic pain. Journal of Pain. 2008;9(6):506-21.
Citations - Implementation Examples
Related What Works for Health Strategies
To see citations and implementation resources for this strategy, visit:
To see all strategies: