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U.S.A."],"published-print":{"date-parts":[[2026,11,3]]},"abstract":"<jats:p>Spending time outdoors provides opportunities for physical activity, exposure to natural light, and social contact. Although young people\u2019s time use has changed substantially in recent decades, little is known about long-term trends in adolescents\u2019 outdoor engagement. This question is especially important because adolescence is a period of major life transitions and the development of lasting behavioral habits. This study examines 20-y trends in time spent outdoors among American adolescents using time-diary data from 14,235 individuals aged 15 to 19 in the 2003\u20132023 American Time Use Survey, a nationally representative survey of the US population. We describe trends in outdoor exposure and examine associations between outdoor time and leisure behaviors, including computer use for leisure, indoor physical activity, and time spent with friends. We find that outdoor engagement among boys has declined sharply, erasing a long-standing male advantage and causing boys\u2019 participation levels to converge with girls\u2019 at similarly low rates. Greater time spent in computer-based leisure was associated with less outdoor time, particularly among boys, whereas time spent with friends was positively associated with outdoor engagement for both sexes. Indoor physical activity did not change over the observation period and did not offset declines in outdoor time. These findings suggest that broader changes in leisure activities may be reshaping how young people engage with outdoor environments. Further research is needed to better understand the factors underlying these trends and their potential long-term implications.<\/jats:p>","DOI":"10.1073\/pnas.2605134123","type":"journal-article","created":{"date-parts":[[2026,10,26]],"date-time":"2026-10-26T19:06:31Z","timestamp":1793041591000},"update-policy":"https:\/\/doi.org\/10.1073\/pnas.cm10313","source":"Crossref","is-referenced-by-count":0,"title":["Changes in American adolescents\u2019 outdoor time over two decades"],"prefix":"10.1073","volume":"123","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-9455-0334","authenticated-orcid":false,"given":"Ewa","family":"Jarosz","sequence":"first","affiliation":[{"id":[{"id":"https:\/\/ror.org\/01xtthb56","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Psychology, University of Oslo","place":["Oslo, Norway"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7160-1298","authenticated-orcid":false,"given":"Vidar","family":"Ulset","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/045016w83","id-type":"ROR","asserted-by":"publisher"}],"name":"Norwegian School of Sport Sciences, Department of Teacher Education and Outdoor Studies","place":["Oslo, Norway"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1647-3246","authenticated-orcid":false,"given":"Vegard","family":"Skirbekk","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/01xtthb56","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Psychology, University of Oslo","place":["Oslo, Norway"]},{"id":[{"id":"https:\/\/ror.org\/046nvst19","id-type":"ROR","asserted-by":"publisher"}],"name":"Norwegian Institute of Public Health, Centre for Fertility and Health","place":["Oslo, Norway"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"341","published-online":{"date-parts":[[2026,10,26]]},"reference":[{"key":"e_1_3_4_1_2","doi-asserted-by":"publisher","DOI":"10.2304\/ciec.2004.5.1.10"},{"key":"e_1_3_4_2_2","unstructured":"B. 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