{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,17]],"date-time":"2026-09-17T05:03:43Z","timestamp":1789621423133,"version":"build-2803163510"},"reference-count":51,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,9,17]],"date-time":"2026-09-17T00:00:00Z","timestamp":1789603200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Public Health"],"abstract":"<jats:sec>\n                    <jats:title>Introduction<\/jats:title>\n                    <jats:p>The COVID-19 pandemic substantially affected people who use drugs (PWUD) with comorbid psychiatric disorders. Lockdowns, shifts in drug markets, and fear of infection may have altered drug-use patterns. This prospective study examined changes in drug-use behaviors among PWUD with comorbid psychiatric disorders and identified factors associated with these changes across three distinct phases of the COVID-19 pandemic.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>A cohort of adult PWUD with ICD-10-defined comorbid psychiatric disorders was followed longitudinally from March 2021 to January 2024. Drug-use behaviors were assessed at three time points: during the active COVID-19 pandemic period, after receipt of at least two doses of a World Health Organization (WHO)-endorsed COVID-19 vaccine, and after the WHO declared the end of the global pandemic. Structured interviews and standardized rating scales were used to assess demographic characteristics, ICD-10 comorbid psychiatric disorders, drug-use behaviors, DSM-5 substance use disorder severity, and psychological dependence. COVID-19 infection history and vaccination status were verified through centralized electronic health records. Within-person changes in drug-use behaviors across time points and factors associated with these changes were examined using mixed-effects models.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>One hundred and thirty participants (mean age 40.03\u202fyears) completed the study. The majority (62.3%) had a comorbid substance-induced psychotic disorder. Overall, 27.7% had laboratory-confirmed COVID-19 infection during the study period. Across the three phases, participants demonstrated significant reductions in substance use disorder severity and drug-use frequency. Sharing of drug-use equipment also declined and remained lower after the pandemic. Greater worry about contracting COVID-19 was associated with increased avoidance of drug use with others and reduced sharing of drug-use equipment. Prior COVID-19 infection was associated with lower drug-use frequency. Among individual drugs, cough syrup was uniquely linked to more frequent use, less solitary use, and sustained reductions in equipment sharing.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>Adult PWUD with comorbid psychiatric disorders demonstrated sustained improvements in drug-use behaviors throughout the COVID-19 pandemic and after its official conclusion. Both prior COVID-19 infection and greater worry about contracting COVID-19 were associated with these positive behavioral changes.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.3389\/fpubh.2026.1878232","type":"journal-article","created":{"date-parts":[[2026,9,17]],"date-time":"2026-09-17T04:29:29Z","timestamp":1789619369000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Changes in drug-use behaviors among people who use drugs with comorbid psychiatric disorders across the COVID-19 pandemic: a three-phase longitudinal cohort study"],"prefix":"10.3389","volume":"14","author":[{"given":"Albert Kar Kin","family":"Chung","sequence":"first","affiliation":[{"name":"Department of Psychiatry, Li Ka Shing Faculty of Medicine, The University of Hong Kong","place":["Pokfulam, Hong Kong SAR, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Johnson Kai Chun","family":"Law","sequence":"additional","affiliation":[{"name":"Department of Psychiatry, Li Ka Shing Faculty of Medicine, The University of Hong Kong","place":["Pokfulam, Hong Kong SAR, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sau Wan","family":"Tang","sequence":"additional","affiliation":[{"name":"Department of Psychiatry, Li Ka Shing Faculty of Medicine, The University of Hong Kong","place":["Pokfulam, Hong Kong SAR, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Cheuk Yin","family":"Tse","sequence":"additional","affiliation":[{"name":"Department of Psychiatry, Li Ka Shing Faculty of Medicine, The University of Hong Kong","place":["Pokfulam, Hong Kong SAR, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jerome Jun Hao","family":"Chen","sequence":"additional","affiliation":[{"name":"Department of Psychiatry, Li Ka Shing Faculty of Medicine, The University of Hong Kong","place":["Pokfulam, Hong Kong SAR, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2026,9,17]]},"reference":[{"key":"ref1","volume-title":"Global status Report on Alcohol and Health and Treatment of Substance use Disorders","year":"2024"},{"key":"ref2","doi-asserted-by":"publisher","first-page":"999","DOI":"10.3390\/jcm13040999","article-title":"Navigating the complex intersection of substance use and psychiatric disorders: a comprehensive review","volume":"13","author":"Bahji","year":"2024","journal-title":"J Clin Med"},{"key":"ref3","doi-asserted-by":"publisher","first-page":"157","DOI":"10.23750\/abm.v91i1.9397","article-title":"WHO declares COVID-19 a pandemic","volume":"91","author":"Cucinotta","year":"2020","journal-title":"Acta Biomed"},{"key":"ref4","volume-title":"COVID-19 cases. 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