The question of whether the legalization of cannabis should be promoted can be considered from different perspectives from a scientific point of view. For negative consequences to result from cannabis legalization, several conditions must be met. First, legalization of cannabis must result in a larger portion of the population beginning to use cannabis. Second, cannabis use would have to cause negative behavior or negative health outcomes. Although the scientific literature on these issues is sparse, there are publications that can help us shed light on this matter.
Thanks to the wave of legalization in the United States in the 2010s, there are now several studies that use modern statistical methods to analyze the effects of legal cannabis on the population.[1] One of the most important questions to answer relates to changes in population use.
The scientists, who tried to answer this question with American data, came to a not so surprising conclusion: about three percent of the population, which did not regularly use cannabis before legalization, now reported to use cannabis regularly. Interestingly, one of the two studies found not only an increase in cannabis use, but also a reduction in the use of other drugs and in excessive alcohol consumption.
That settles the first question: the scientific literature indicates that legalizing cannabis increases the percentage of the population that uses it. The question remains, how does cannabis affect the user?
How does cannabis actually work?
Research addressing the consequences of cannabis use is unfortunately inconclusive and often poor in quality. Two large review studies on the topic of cannabis, respiratory diseases and lung cancer from 2005 and 2007 describe this aptly: on the one hand, there is a large discrepancy in the quality of the studies, on the other hand, there is no consistent link between cannabis use and lung cancer as soon as tobacco use is included.[1]
A second way cannabis use could negatively impact the population would be through changing the behavior of users. Clear causal research on this is also still lacking today. A comprehensive 2016 analysis found that although cannabis users were observed to have increased lack of motivation and lower cognitive abilities, it was not clear whether these effects were long-lasting and in which direction causality ran.[2] That is, it is not clear whether increased lack of motivation is the trigger for cannabis use or vice versa.
Similarly, studies have looked at other behavioral changes triggered by cannabis use. Whether research on domestic violence or road danger, the literature tends to attribute a positive effect to cannabis legalization, usually in combination with a reduction in alcohol use[3].
However, since these studies also fail to separate cause from effect, there is only one conclusion that remains: in order to assess the physical and psychological consequences of cannabis legalization on an evidence-based level, we absolutely need more research and pilot projects on this topic. The Cannabis Research Association strives to fund and conduct such high quality research.
[1] Sabia, J. J., Dave, D. M., Alotaibi, F., & Rees, D. I. (2021). Is Recreational Marijuana a Gateway to Harder Drug Use and Crime? (No. w29038). National Bureau of Economic Research. ; Dragone, D., Prarolo, G., Vanin, P., & Zanella, G. (2019). Crime and the legalization of recreational marijuana. Journal of economic behavior & organization, 159, 488-501.
[2] Tetrault, J. M., Crothers, K., Moore, B. A., Mehra, R., Concato, J., & Fiellin, D. A. (2007). Effects of marijuana smoking on pulmonary function and respiratory complications: a systematic review. Archives of internal medicine, 167(3), 221-228 ; Mehra, R., Moore, B. A., Crothers, K., Tetrault, J., & Fiellin, D. A. (2006). The association between marijuana smoking and lung cancer: a systematic review. Archives of internal medicine, 166(13), 1359-1367.
[3] Volkow, N. D., Swanson, J. M., Evins, A. E., DeLisi, L. E., Meier, M. H., Gonzalez, R., … & Baler, R. (2016). Effects of cannabis use on human behavior, including cognition, motivation, and psychosis: a review. JAMA psychiatry, 73(3), 292-297
[4] Smith, P. H., Homish, G. G., Collins, R. L., Giovino, G. A., White, H. R., & Leonard, K. E. (2014). Couples’ marijuana use is inversely related to their intimate partner violence over the first 9 years of marriage. Psychology of Addictive Behaviors, 28(3), 734 ; Mark Anderson, D., Hansen, B., & Rees, D. I. (2013). Medical marijuana laws, traffic fatalities, and alcohol consumption. The Journal of Law and Economics, 56(2), 333-369.
