biostudies-literatureChaffee BWNHLBI NIH HHS715-722https://www.ebi.ac.uk/biostudies/studies/S-EPMC8094031biostudies-literatureUnknown175(7)<h4>Importance</h4>Stay-at-home policies related to the COVID-19 pandemic could disrupt adolescents' substance use and physical activity.<h4>Objective</h4>To compare adolescents' substance use and physical activity behaviors before and after stay-at-home restrictions.<h4>Design, setting, and participants</h4>Ongoing prospective cohort study of tobacco use behaviors among ninth- and tenth-grade students enrolled at 8 public high schools in Northern California from March 2019 to February 2020 and followed up from September 2019 to September 2020. Race/ethnicity was self-classified from investigator-provided categories and collected owing to racial/ethnic differences in tobacco and substance use.<h4>Exposures</h4>In California, a COVID-19 statewide stay-at-home order was imposed March 19, 202JAMA pediatricsAdolescents' Substance Use and Physical Activity Before and During the COVID-19 Pandemic.PMC8094031U54 HL147127Chaffee BWHoeft KSHalpern-Felsher BCouch ETCheng JfalseAdolescents' Substance Use and Physical Activity Before and During the COVID-19 Pandemic.<h4>Importance</h4>Stay-at-home policies related to the COVID-19 pandemic could disrupt adolescents' substance use and physical activity.<h4>Objective</h4>To compare adolescents' substance use and physical activity behaviors before and after stay-at-home restrictions.<h4>Design, setting, and participants</h4>Ongoing prospective cohort study of tobacco use behaviors among ninth- and tenth-grade students enrolled at 8 public high schools in Northern California from March 2019 to February 2020 and followed up from September 2019 to September 2020. Race/ethnicity was self-classified from investigator-provided categories and collected owing to racial/ethnic differences in tobacco and substance use.<h4>Exposures</h4>In California, a COVID-19 statewide stay-at-home order was imposed March 19, 2022021-01-01T00:00:00Z2021 Jul2026-07-16T12:01:29.148Z2025-04-04T10:16:09.65ZS-EPMC80940313393892210.1001/jamapediatrics.2021.0541