{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,25]],"date-time":"2026-09-25T09:10:58Z","timestamp":1790327458975,"version":"4.1.0"},"reference-count":33,"publisher":"Wiley","issue":"9","license":[{"start":{"date-parts":[[2026,9,15]],"date-time":"2026-09-15T00:00:00Z","timestamp":1789430400000},"content-version":"vor","delay-in-days":14,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2026,9,1]],"date-time":"2026-09-01T00:00:00Z","timestamp":1788220800000},"content-version":"tdm","delay-in-days":0,"URL":"http:\/\/doi.wiley.com\/10.1002\/tdm_license_1.1"}],"funder":[{"DOI":"10.13039\/501100001711","name":"Schweizerischer Nationalfonds zur F\u00f6rderung der Wissenschaftlichen Forschung","doi-asserted-by":"publisher","award":["#218408"],"award-info":[{"award-number":["#218408"]}],"id":[{"id":"10.13039\/501100001711","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001711","name":"Schweizerischer Nationalfonds zur F\u00f6rderung der Wissenschaftlichen Forschung","doi-asserted-by":"publisher","award":["#33FI\u20100_229621"],"award-info":[{"award-number":["#33FI\u20100_229621"]}],"id":[{"id":"10.13039\/501100001711","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["J Int AIDS Soc."],"published-print":{"date-parts":[[2026,9]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                  <jats:sec>\n                    <jats:title>Introduction<\/jats:title>\n                    <jats:p>Global awareness to chemsex, a specific form of sexualized psychoactive substance (\u201cchems\u201d) use among gay, bisexual and other men who have sex with men (gbMSM), is increasing. We aimed to assess prevalence, patterns and implications of \u201cchems\u201d use on chemsex\u2010related outcomes.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>We conducted a Swiss\u2010wide longitudinal study using individual\u2010level data from April 2019 to December 2024 of adult gbMSM with HIV, enrolled in the Swiss HIV Cohort Study (SHCS), or taking HIV pre\u2010exposure prophylaxis (PrEP), enrolled in SwissPrEPared. Determinants of \u201cchems\u201d (methamphetamine, new psychoactive stimulants, GHB\/GBL) use and clinical implications were analysed using logistic regression. Longitudinal \u201cchems\u201d use patterns were distinguished by rule\u2010based classification. Point\u2010prevalences of \u201cchems\u201d use, including COVID\u201019 and mpox periods, were analysed using interrupted time series analysis.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>We analysed 107,855 follow\u2010up visits from 13,304 gbMSM. \u201cChems\u201d were used by 17.2% of gbMSM (21.4% in SwissPrEPared vs. 11.2% in the SHCS). Age below 26 (compared to 26\u221237, adjusted odds ratio [aOR]: 0.82, 95%\u2010confidence interval: 0.68\u22120.96), over 37 (aOR for 38\u221248: 0.84, 0.75\u22120.94; aOR for over 48: 0.54, 0.47\u22120.62) and bisexual orientation showed lower odds (aOR: 0.78, 0.66\u22120.90), while participation in French\u2010speaking SwissPrEPared centres (aOR compared to SHCS Eastern Switzerland: 1.41, 1.22\u22121.64) and sex with non\u2010steady partners showed higher odds for \u201cchems\u201d use (aOR: 12.44, 8.85\u221218.17). \u201cChems\u201d use was associated with depression, inconsistent condom use, high non\u2010steady partner count and sexually transmitted infections (STIs). Comparing longitudinal use patterns, temporally restricted use, that is, recovering from stable use, reported \u201cchems\u201d use only once, or for a single episode shorter than 1 year, showed the lowest risk for STIs and high partner count, whereas intermittent use showed lower risk only for syphilis. \u201cChems\u201d use decreased marginally during COVID\u201019 and mpox, with a quick return and no difference to levels before COVID\u201019.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>A large proportion of gbMSM use \u201cchems,\u201d with congruent determinants across both cohorts but heterogeneous impact on sexual and mental health that varies by specific substance and longitudinal use patterns. Further understanding of underlying mechanisms driving this heterogeneity is needed before delivering mechanism\u2010informed interventions tailored to \u201cchems\u201d use patterns, like STI and depression screening, harm\u2010reduction counselling and linkage to addiction care.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1002\/jia2.70199","type":"journal-article","created":{"date-parts":[[2026,9,15]],"date-time":"2026-09-15T08:13:55Z","timestamp":1789460035000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Prevalence, Patterns and Implications of Chemsex Substance Use Among Gay and Bisexual Men Who Have Sex With Men: A Cohort\u2010Collaboration Between the Swiss HIV Cohort Study and the SwissPrEPared Study"],"prefix":"10.1002","volume":"29","author":[{"ORCID":"https:\/\/orcid.org\/0009-0005-4095-0152","authenticated-orcid":false,"given":"Bashkim","family":"Jaha","sequence":"first","affiliation":[{"name":"Division of Infectious Diseases and Hospital Epidemiology University Hospital Zurich  Zurich Switzerland"},{"name":"Institute of Medical Virology University of Zurich  Zurich Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0830-0927","authenticated-orcid":false,"given":"Andrea","family":"Farnham","sequence":"additional","affiliation":[{"name":"Department of Public &amp; Global Health, Epidemiology, Biostatistics and Prevention Institute University of Zurich  Zurich Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9220-8348","authenticated-orcid":false,"given":"Roger","family":"Kouyos","sequence":"additional","affiliation":[{"name":"Division of Infectious Diseases 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