@article{ref1,
title="Historical trends in the grade of onset and sequence of cigarette, alcohol, and marijuana use among adolescents from 1976-2016: implications for "Gateway" patterns in adolescence",
journal="Drug and alcohol dependence",
year="2018",
author="Keyes, Katherine M. and Rutherford, Caroline and Miech, Richard A.",
volume="194",
number="",
pages="51-58",
abstract="INTRODUCTION: In the past decade, marijuana use prevalence among adolescents has remained relatively steady while cigarette and alcohol prevalence has declined. We examined historical trends in: average grade of onset of marijuana, alcohol, and cigarette use by 12<sup>th</sup> grade; proportion who try alcohol/cigarettes before first marijuana use, among those who use by 12<sup>th</sup> grade; and conditional probability of marijuana use by 12<sup>th</sup> grade after trying alcohol/cigarettes. <br><br>METHODS: Data were drawn from 40 yearly, cross-sectional surveys of 12<sup>th</sup> grade US adolescents. A subset of students (N = 246,050) were asked when they first used each substance. We reconstructed cohorts of substance use from grade-of-onset to determine sequence of drug use, as well as probability of marijuana use in the same or later grade. <br><br>RESULTS: Average grade of first alcohol and cigarette use by 12<sup>th</sup> grade increased across time; e.g., first cigarette increased from grade 7.9 in 1986 to 9.0 by 2016 (β=0.04, SE = 0.001, p < 0.01). The proportion of 12<sup>th</sup> grade adolescents who smoke cigarettes before marijuana fell below 50% in 2006. Each one-year increase was associated with 1.11 times increased odds of first cigarette in a grade after first marijuana (95% C.I. 1.11-1.12). Among those who initiate alcohol/cigarettes prior to marijuana by 12<sup>th</sup> grade, the probability of subsequent marijuana use is increasing. <br><br>CONCLUSION: Marijuana is increasingly the first substance in the sequence of adolescent drug use. Reducing adolescent smoking has been a remarkable achievement of the past 20 years; those who continue to smoke are at higher risk for progression to marijuana use.<br><br>Copyright © 2018 Elsevier B.V. All rights reserved.<p /> <p>Language: en</p>",
language="en",
issn="0376-8716",
doi="10.1016/j.drugalcdep.2018.09.015",
url="http://dx.doi.org/10.1016/j.drugalcdep.2018.09.015"
}