To the Editor On behalf of our coauthors, we write to respond to concerns raised about the methods and analyses for the Research Letter, “Association of Marijuana Legalization With Marijuana Use Among US High School Students, 1993-2019,” published in JAMA Network Open on September 7, 2021.1 These concerns were brought to our attention by readers and subsequently published as Comments with the article.2,3 In this study, we used data from the Youth Risk Behavior Survey (YRBS) for the period 1993 to 2019 to provide updated estimates of the association of legalization of recreational marijuana and legalization of medical marijuana with adolescent marijuana use.
For our analyses, we used unweighted and pooled national and state YRBS data. While this unweighted and pooled approach maximized the number of state policy changes used to identify the effect of marijuana legalization on youth marijuana use for the average student in the pooled sample, published Comments advised that the approach was inappropriate for the following reasons: (1) “Pooling national and state YRBS data is inappropriate because underlying person-level weights are different, and there is some overlap between national and state YRBS data; thus, a student could be represented more than once. The YRBS codebook explicitly warns against combining these data.” And “YRBS data are designed to be weighted to capture representative populations”3 In addition, unweighted and pooled analyses may produce results that are not generalizable. At the request of the editors, we have reconducted separate analyses with weighted and unpooled data for the national and state estimates.
We had previously reported that medical marijuana law (MML) adoption was associated with a statistically significant decrease in the odds of marijuana use among adolescents and that 2 or more years after adoption, recreational marijuana laws (RMLs) were associated with a statistically significant decrease in the odds of marijuana use among adolescents. After reconducting the analyses with weighted and unpooled data, RML adoption and MML adoption were no longer statistically significantly associated with adolescent marijuana use. Moreover, in the corrected analysis, we found that 4 or more years after MML adoption, marijuana use among adolescents declined (OR, 0.83; 95% CI, 0.68-0.99; P = .049), as noted in the Figure in the replacement article.1 The changes in findings may be indicative of heterogeneity in the associations of MMLs with adolescent marijuana use across states.
We apologize to the readers and editors of JAMA Network Open for any confusion we caused by conducting our prior analysis based on unweighted and pooled data when the YRBS recommends that the correct approach is to use weighted and unpooled data. The editors have requested that the original article be retracted and replaced with the correct analyses and findings based on weighted and unpooled YRBS data.1 These changes affect the text, Table, and Figure. The replacement article includes new supplements with a copy of the original article with the errors highlighted and another copy with the corrections highlighted.
Published: March 8, 2022. doi:10.1001/jamanetworkopen.2022.1473
Open Access: This is an open access article distributed under the terms of the CC-BY License. © 2022 Anderson DM et al. JAMA Network Open.
Corresponding Author: D. Mark Anderson, PhD, Department of Agricultural Economics and Economics, Montana State University, PO Box 172920, Bozeman, MT 59717-2920 (dwight.anderson@montana.edu).
Conflict of Interest Disclosures: Dr Sabia reported receiving grants from Charles Koch Foundation and Troesh Family Foundation during the conduct of the study. No other disclosures were reported.