Cannabis’ Impact on Health Justifies Its Legalization, Not Its Criminal Prohibition

In July 2011, the Obama Administration rebuffed an administrative petition filed by a coalition of public interest organizations, including NORML, which sought to reassess cannabis’ Schedule I status under federal law. Yet little if any scientific basis exists to justify the federal government’s present prohibitive stance, and there is ample scientific and empirical evidence to rebut it. This evidence includes safety data substantiated over thousands of years of human use as well as the conclusions of hundreds of modern preclinical and clinical trials. In recent years, scientists have assembled sufficient evidence establishing that cannabis is objectively safe and that it possesses many important therapeutic properties.

Humans have cultivated and consumed the flowering tops of the female cannabis plant, colloquially known as marijuana, since virtually the beginning of recorded history. Cannabis-based textiles dating to 7,000 B.C. have been recovered in northern China, and the plant’s use as a medicinal and euphoric agent date back nearly as far. In 2008, archeologists in Central Asia discovered over two pounds of cannabis in the 2,700-year-old grave of an ancient shaman. After scientists conducted extensive testing on the material’s potency, they affirmed, “[T]he most probable conclusion … is that [ancient] culture[s] cultivated cannabis for pharmaceutical, psychoactive, and divinatory purposes.”[1]

Modern cultures continue to use cannabis for these same purposes, despite a present-day, virtual worldwide ban on the plant’s cultivation and use. In the United States, federal prohibitions outlawing cannabis’ recreational, industrial, and therapeutic use were first imposed by Congress under the Marihuana Tax Act of 1937 and then later reaffirmed by federal lawmakers’ decision to classify marijuana – as well as all of the plant’s active compounds, known as cannabinoids – as a Schedule I substance under the Controlled Substances Act of 1970. This classification, which asserts by statute that cannabis is equally as dangerous to the public as heroin, defines cannabis and its dozens of distinct cannabinoids as possessing “a high potential for abuse … no currently accepted medical use, … [and] a lack of accepted safety for the use of the drug … under medical supervision.” By contrast, cocaine and methamphetamine – which remain illicit for recreational use but may be consumed under a doctor’s supervision – are classified as Schedule II drugs; examples of Schedule III and IV substances include anabolic steroids and Valium, respectively, while codeine-containing analgesics are defined by a law as Schedule V drugs, the federal government’s most lenient classification.

Despite the U.S. government’s nearly century-long prohibition of the plant, cannabis is nonetheless one of the most investigated therapeutically active substances in history. To date, there are over 20,000 published studies or reviews in the scientific literature pertaining to the cannabis plant and its cannabinoids. Remarkably, nearly one-third of these were published within the last three years. This total includes over 2,700 separate papers published in 2009, 1,950 papers published in 2010, and another 2,100 published to date in 2011 according to a key word search on the search engine PubMed Central, the U.S. government repository for peer-reviewed scientific research.

The scientific conclusions of the overwhelming majority of these recent papers directly conflict with the federal government’s stance that cannabis is a highly dangerous substance worthy of the harshest criminalization. Modern scientific scrutiny of the cannabis plant reveals that its active constituents are uniquely safe and are effective therapeutic compounds. Unlike most prescription or over-the-counter medications, cannabinoids are incapable of causing the user to experience a fatal overdose, and they are virtually nontoxic to healthy cells or organs.[2] According to annual data reported by the FDA’s Adverse Events Reporting System, deaths in the United States attributable to conventional medications climbed to over 82,000 in 2010, more than a 300 percent increase in mortality since the year 2000.[3] Yet during this same ten-year period, there are no reports of deaths induced by cannabis overdose or marijuana-induced toxicity.

Scientific study of the cannabis plant has now identified over 60 unique, active cannabinoids – such as THC, THCV, CBD, THCA, CBC, and CBG, among others – many of which possess distinctive and important therapeutic properties. A recent meta-analysis of these compounds documents well over a dozen therapeutic properties attributable to cannabinoids, including neuroprotective, anti-cancer, anti-bacterial, and anti-diabetic properties.[4] In 2010, the results of a series of randomized, placebo-controlled FDA-approved clinical trials performed by regional branches of the University of California established that inhaled cannabis possessed therapeutic utility that is comparable to or better than many conventional medications, particularly in the treatment of multiple sclerosis and neuropathic pain.[5] These findings echoed those of a recent report issued by the American Medical Association’s Council on Science and Public Health, which declared, “Results of short term controlled trials indicate that smoked cannabis reduces neuropathic pain, improves appetite and caloric intake especially in patients with reduced muscle mass, and may relieve spasticity and pain in patients with multiple sclerosis.”[6]

Since 2005, there have been an estimated 40 controlled studies assessing the safety and efficacy of cannabinoids, involving over 2,500 subjects.[7] Most legally approved drugs go through far fewer clinical trials involving far fewer subjects. Nevertheless, earlier this year Michele Leonhart, the Director of the United States Drug Enforcement Administration, declared in the Federal Register: “There are no adequate and well-controlled studies proving (marijuana’s) efficacy. … At this time, the known risks of marijuana use have not been shown to be outweighed by specific benefits.”[8]

Yet an objective review of the scientific literature finds that the supposed “known risks” associated with marijuana appear to be specious and unpersuasive, particularly when cannabis consumption is compared to the use of other legal intoxicating substances. For example, a recent assessment of the long-term effects of cannabis exposure on health in the peer-reviewed scientific journal Current Opinion in Pharmacology concluded, “Overall, by comparison with other drugs used mainly for ‘recreational’ purposes, cannabis could be rated a relatively safe drug.”[9]

This finding is hardly surprising. A significant portion of western civilization has used cannabis as a therapeutic agent or recreational intoxicant for thousands of years with relatively few adverse consequences – either to the individual user or to society. According to ethnographers at the University of Alberta, Canada, “Most adult marijuana users regulate use to their recreational time and do not use compulsively. … Generally, participants reported using marijuana because it enhanced relaxation and concentration, making a broad range of leisure activities more enjoyable and pleasurable.”[10]

Several objective bodies have sought to assess the potential costs that marijuana use may impose on modern society. These calculations have consistently estimated the social costs associated with marijuana’s use to be relatively minimal. For example, a 2009 assessment published in the British Columbia Mental Health and Addictions Journal estimated that health-related costs per user are eight times higher for drinkers of alcoholic beverages than they are for those who use cannabis, and are more than 40 times higher for tobacco smokers.[11] “In terms of [health-related] costs per user: tobacco-related health costs are over $800 per user, alcohol-related health costs are much lower at $165 per user, and cannabis-related health costs are the lowest at $20 per user,” investigators concluded.

In fact, no less than the World Health Organization has concluded: “Overall, most of these risks (associated with marijuana) are small to moderate in size. In aggregate they are unlikely to produce public health problems comparable in scale to those currently produced by alcohol and tobacco. On existing patterns of use, cannabis poses a much less serious public health problem than is currently posed by alcohol and tobacco in Western societies.”[12] As is often the case with findings that contradict the U.S. government’s official position, this conclusion was ultimately redacted by WHO after an intense lobbying campaign by U.S. officials who argued that such an acknowledgment by the agency could undermine America’s ongoing prohibition.[13]

Of course, none of the above statements are intended to imply that marijuana poses no risks whatsoever to the consumer or that cannabis cannot be abused in certain settings. Cannabis is mood altering. It may temporarily interfere with certain cognitive and decisionmaking skills. It may possess certain short-term, adverse physiological impacts on the body (such as rapidly increased heart rate), and it may induce dependence in a minority of its users. Heavy maternal use of cannabis during the first and third trimester has been associated with neurobehavioral deficits in some children.[14] Chronic use of the substance among young people, particularly those who may be predisposed to certain mental illnesses such as depression and schizophrenia, may also be associated with increased neurological risks.[15] Finally, cannabis smoke contains several known carcinogens and potential lung irritants. However, the ingestion of cannabis via alternative methods such as edibles, liquid tinctures, or via a vaporizer – a process whereby the plant’s cannabinoids are heated to the point of vaporization but below the point of combustion – virtually eliminates consumers’ exposure to such unwanted risk factors.

There are other potential risks associated with cannabis as well, though these are largely factors associated with the drug’s criminal prohibition rather than with the substance itself. For example, the marijuana sold on the street today is often of unknown purity and quality. Further, the product’s marketers are typically criminal entrepreneurs who may also introduce consumers to other, more potent illicit substances. Finally, the black-market inflated price of cannabis exposes its producers and consumers to potential crime and theft from other criminal entities looking to exploit the drug’s prohibition-inflated economic value.

Ultimately, however, none of the potential health risks associated with the adult, responsible use of cannabis in any objective way justify the substance’s present Schedule I prohibitive status or legitimize the use of state and federal force to restrict consumers from engaging in the plant’s production, distribution, or consumption. Nor do they justify the Obama Administration’s present heavy-handed attempts to interfere with the rule of law in states that have enacted policies that diverge from that of the federal government’s.

The concerns raised by federal lawmakers and the present administration[16] regarding the potential health implications of cannabis do not validate the drug’s continued criminalization. Just the opposite is true. There are numerous adverse health consequences associated with alcohol, tobacco, and prescription pharmaceuticals – all of which modern scientific inquiry has determined to be far more dangerous and costlier to society than cannabis – and it’s precisely because of these consequences that these products are legally regulated and their use is restricted to particular consumers and specific settings. Similarly, a pragmatic regulatory framework allowing for the limited legal use cannabis by adults would best mitigate the health risks associated with the drug’s use and abuse. At a minimum, this framework would require federal lawmakers to reschedule cannabis from its archaic and unscientific Schedule I prohibitive status. At best, such a scheme would demand that cannabis be ‘descheduled’ and removed the from the federal Controlled Substances Act altogether.


[1] Russo et al. 2008. Phytochemical and genetic analyses of ancient cannabis from central Asia. Journal of Experimental Botany 59: 4171-4182.

[2] Wayne Hall. A comparative appraisal of the health and psychological consequences of alcohol, cannabis, nicotine, and opiate use. National Drug and Alcohol Research Centre, University of New South Wales, 1995.

[3] United States Food and drug Administration, AERTS Patient Outcomes by Year (as of December 31, 2010).

[4] Izzo et al. 2009. “Non-psychotropic plant cannabinoids: new therapeutic opportunities from an ancient herb.” Trends in Pharmacological Sciences 30: 515-527.

[5] Center for Medicinal Cannabis Research.
Report to the Legislature and Governor of the State of California
, 2010 (pdf).

[6] American Medical Association. Report of the Council on Scientific and Public Health: Use of Cannabis for Medical Purposes, 2009 (pdf).

[7] Arno Hazekamp and Franjo Grotenhermen. 2010. “Review on clinical studies with cannabis and cannabinoids: 2005-2009.” Cannabinoids 5: 1-21.

[8] United States Drug Enforcement Administration. July 8, 2011. “Denial of Petition to Initiate Proceedings to Reschedule Marijuana.” Federal Register 76: 40559-405582.

[9] Leslie Iversen. 2005. Long-term effects of exposure to cannabis. Current Opinion in Pharmacology 5: 69-72.

[10] Osborne et al. 2008. Understanding the motivations for recreational marijuana use among Canadians. Substance Use and Misuse 43: 581-583.

[11] Gerald Thomas and Chris Davis. 2009. Cannabis, tobacco and alcohol use in Canada: comparing risks of harm and costs to society. Visions: BC’s Mental Health and Addictions Journal 5: 11.

[12] Hall. Op. cit.

[13] David Concar, “High anxieties: What WHO doesn’t want you to know about cannabis,” New Scientist, February 21, 2008.

[14] Minnes et al. 2011. Prenatal tobacco, marijuana, stimulant, and opiate exposure: outcomes and practice implications. Addiction Science and Clinical Practice 6: 57-70.

[15] The Beckley Foundation. Cannabis and Mental Health: Responses to the Emerging Evidence, April 2006 (pdf).

[16] Gil Kerlikowske. What We Have to Say About Legalizing Marijuana: Official White House Response to ‘Legalize and Regulate Marijuana in a Manner Similar to Alcohol’ and 7 other petitions. October 29, 2011.

Also from this issue


  • Paul Armentano begins our roundtable discussion with a review of the burgeoning literature on the safety of recreational cannabis and the unique effectiveness of cannabis for many medical purposes. Recent years have seen an outpouring of this type of research, which stands in stark contrast to the political consensus in Washington, which still favors criminalization.

  • Norm Stamper argues that when people see the true face of the War on Drugs, they are justifiably outraged. The average citizen can now take videos almost anywhere and then publicize what they’ve recorded. The result? YouTube clips of military-style police raids, in which the violence meted out seems vastly disproportionate to any possible wrongdoing by the suspects. Police have an important job to do in our society. They need the public’s respect if they’re going to succeed, and the War on Drugs is getting in the way.

  • Allen St. Pierre, the executive director of NORML, surveys the political landscape of cannabis Prohibition. He finds significant disparity between public opinion and federal policy; even so, state policies have been much more susceptible to change. Among many other suggestions, he urges advocates to confront the “fear factor” surrounding cannabis, to win more diverse political allies, and to be more open about being “pot tolerant.”

  • Morgan Fox argues that marijuana both can and should be integrated into the American economy and American civil society. He notes that while taxation and regulation of marijuana may be causes for concern among some growers and users, the “regulation” we have now is undoubtedly worse, because it means only criminals are allowed to grow the nation’s largest cash crop. With public support for legalization at 50%, he nonetheless acknowledges that politicians have been slow to adopt the issue, and federal Prohibition is still likely to last for quite some time.