You Cannot Spell "Healthcare" Without "THC": What Are the Effects of Marijuana on Public Health?

In 2012, the states of Colorado and Washington legalized recreational marijuana. Since then, recreational marijuana has been made legal in a total of 21 U.S. states and Washington, D.C. Other countries have legalized marijuana, including Mexico, Uruguay, Georgia, South Africa, Canada, Thailand, and Malta. While progress has been made on marijuana legalization, there is still progress that still needs to be made, particularly when it comes to public opinion. Polling finds that how people perceive marijuana as overall good is split. According to Gallup, 53 percent believe marijuana has a positive effect on individual marijuana users, whereas 49 percent believe it has a positive effect on society. As we see below, those who have tried marijuana have a more positive view on marijuana than those who have not. 

In honor of this April 20th, I would like to examine the effects that marijuana have had on public health, as opposed to individual health. I do not expect the public health argument for marijuana to be open-and-shut. As I brought up in my argument to legalize psychedelic mushrooms, any substance is going to come with some risk. Marijuana is not an exception to that rule.  

A literature released by the American Economic Association last month was promising (Anderson and Rees, 2023). Not only is there "little credible evidence to suggest that [medical marijuana] legalization promotes marijuana use among teenagers," but there is "convincing evidence that young adults consume less alcohol when medical marijuana is legalized." What about other effects on public health? I will be citing a Cato Institute policy analysis more than once to help answer this important question (Dills et al., 2021).

• Violent crime. I bring up violent crime because the outcomes of violent crime have impact on public health and health services usage. The concern about marijuana when it comes to violent crime is that the THC induces psychosis, which can increase likelihood of violent crime. Conversely, a decrease in crime would be a boon for marijuana proponents to illustrate how legalizing marijuana diverts marijuana sales from underground markets to legal markets. What the Cato Institute found is a disappointment to both sides: "Overall, violent crime has neither soared nor plummeted in the wake of marijuana legalization." A study from the Journal of Drug Issues concluded that medicinal marijuana laws did not have a negative impact on violent or property crime (Shepard et al., 2016). A working paper from Appalachian State University goes as far as arguing that the effects of marijuana on violent crime are in favor of marijuana legalization proponents (Callahan et al., 2021).
• Effects on alcohol use. There was postulation over how marijuana legalization would affect substance use of other substances. Would people trade in one substance for marijuana (substitution effect)? If so, it could be an argument for marijuana proponents since marijuana has been shown to be safer than alcohol. Or would alcohol users use marijuana in addition to the other substance (complementary effect)? According to a study from the National Institutes of Health (NIH), both the substitution and complementary effects exist when it comes to marijuana (Gunn et al., 2022). The Cato Institute points out that there is no clear relation between marijuana legalization and alcohol use.
• Vehicle Fatalities and Accidents. This part is interesting because it is possible that marijuana legalization could make matters worse if more people use marijuana and/or the complementary effect were in full force. On the other hand, if the substitution effect were more prominent than the complementary effect, it could very well improve road safety since marijuana tends to impair less than alcohol. A study from the Journal of Studies on Alcohol and Drugs calculated a 2.3 percent increase in fatal car crashes (Farmer et al., 2022). On the other hand, the Cato Institute went state-by-state to look at the "before/after" rates and compared those to the U.S. average. The Cato Institute found that Oregon notwithstanding, the vehicle fatality rate per 100 million miles driven stayed relatively flat post-legalization. 
• Suicide: This is another metric where the intuition could go either way. Marijuana could be used to treat depression, bipolar, or other behavioral disorders. Excessive marijuana use can also create some others, including schizophrenia and depression. In 2017, the National Academies of Science conducted a lengthy review on marijuana and mental health disorders. The conclusion from NAS was that the findings were mixed and often confounded by alcohol use. Similarly, Cato Institute surmised that "it is difficult to see any association between marijuana legalization and changes in suicide trends." A preprint state-level longitudinal analysis shows a 6.3 percent reduction in suicide (Rich et al., 2021).

Since marijuana legalization is new, the amount of post-legalization data we have is relatively limited. There are only so many conclusions we can draw based on what we have. I think there should be more research to determine the medical, public health, and economic effects of marijuana. This is one of the reasons I have been in favor of removing the DEA's Schedule I designator: so that we can conduct more research on the effects of marijuana. 

We should have a conversation about costs and benefits of marijuana legalization. We need to consider the costs of keeping marijuana in an underground market, as well as the individual and social costs of marijuana legalization. We also need to keep in mind the benefits of each, as well. This conversation about cost-benefit analysis or risk assessment was sorely lacking when politicians implemented lockdowns and other onerous regulations during the COVID pandemic. 

What I will say is that based on what data we currently have, the findings are overall underwhelming. Marijuana legalization does not seem to affect the traffic fatality rate, violent crime rate, alcohol use, or the suicide rate. These findings do not prove that marijuana legalization was the boon to public health that I would have guessed. On the other hand, violent crime, suicides, or vehicle fatalities did not skyrocket. I understand that these issues are multifaceted. But if marijuana were really that bad for public health, you would think that the negative effects would have shown up in the data. 

Correlation does not mean causation. At the same time, you cannot have causation with a correlation in the data, a phenomenon that can similarly be found in the data on gun ownership and gun deaths. From an economic standpoint, I find bans to be blunt instruments that have negative unintended consequences. For those advocating for a ban on or criminalization of marijuana, the burden of proof is on these advocates to show a clear and present danger to public safety and health. With the presently available data, you cannot make the case that marijuana legalization is a menace to public health. If you cannot prove correlation (much less a causation), you cannot even begin to justify such strict measures. Since there is no statistically significant effect on major public health metrics, we should err on the side of freedom and let people smoke their weed in the Land of the Free.