Legalize recreational cannabis in the United States

A new study published in the scientific journal Addiction found that the legalization of recreational cannabis in US states appears to have resulted in an average increase of 20% in the frequency of cannabis use in those states.

The study assessed the effects of legalizing recreational cannabis on a large sample of adult identical twins. Of particular interest were the 111 identical twin pairs in which one twin lived in a state with a different recreational cannabis policy. Twins provide extremely well-matched controls for each other and allow for more accurate estimation of the causal impact of recreational legalization than studies of unrelated individuals.

Looking at all study participants (1,425 people living in states where recreational cannabis use is legal and 1,997 living in states where recreational cannabis use is illegal), the study found an increase of approximately 24% in the average frequency of cannabis use attributable to legalization. Looking only at identical twins living in states with different policies, the twin living in a “legal” state used cannabis about 20% more frequently than his co-twin living in an “illegal” state. These results suggest that recreational legalization has led to an increase in cannabis use.

Cannabis is the most commonly used federal illegal drug in the United States. It is also an addictive substance associated with negative health and psychosocial outcomes. Prior to 2014, cannabis could not be legally bought or sold for recreational use anywhere in the United States. At the start of 2022, more than 141 million Americans lived in a state where cannabis was legal for recreational use.

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For publishers:

This article is free to read for one month after publication from the Wiley Online Library: or by contacting Jean O’Reilly, editorial manager, Addiction[email protected]

To speak with lead author Stephanie Zellers please contact her at the University of Minnesota via email ([email protected]).

Full quote from the article: Zellers SM, Ross JM, Saunders GRB, Ellingson JM, Anderson JE, Corley RP, Iacono W, Hewitt CJ, McGue MK and Vrieze S (2022) Impacts of Recreational Cannabis Legalization on Cannabis Use: A Longitudinal Discordant Twin Study. Addiction:doi:10.1111/add.16016

Funding: This work was supported by the National Institute on Drug Abuse, the National Institute of Mental Health, and the National Institute on Alcohol Abuse and Alcoholism of the National Institutes of Health under award numbers R01DA042755, U01DA046413, R37DA005147, R01DA013240, R01DA036216, R01DA037904, K24DA032555, R01DA035804, P60DA011015, R01DA012845, R01DA038065, R01AA023974, R37AA009367 and R01MH066140. The content is the sole responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health

Declaration of interests: The authors declare that they have no competing interests.

Addiction is a monthly international scientific journal publishing peer-reviewed research reports on alcohol, substances, tobacco and gambling, as well as editorials and other discussion articles. Property of the Society for the Study of Addiction, it has been in continuous publication since 1884.

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of press releases posted on EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.

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