{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,7]],"date-time":"2026-03-07T00:43:15Z","timestamp":1772844195515,"version":"3.50.1"},"posted":{"date-parts":[[2026]]},"group-title":"SSRN","reference-count":0,"publisher":"Elsevier BV","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"abstract":"<jats:p>Few studies have estimated first-episode psychosis (FEP) incidence in Portugal using defined catchment areas and robust population denominators.International evidence suggests FEP incidence may have varied across COVID-19 pandemic phases, potentially reflecting changes in psychosocial stress, service access, and substance use.\u00a0We investigated FEP incidence across five catchment units in the Porto Metropolitan Area, Portugal, from 1 January 2018 to 31 March 2024.\u00a0Cases were identified from inpatient admissions to the Department of Psychiatry, Centro Hospitalar Universit\u00e1rio de S\u00e3o Jo\u00e3o, which serves a defined catchment area; incidence rates were calculated using 2021 Portuguese census denominators.\u00a0Poisson regression was used to estimate incidence rate ratios (IRRs) by sex, age group, and COVID-19 pandemic period (pre-pandemic 2018-2019; pandemic 2020-2022; post-pandemic 2023-Q1 2024), with and without adjustment for cannabis-use frequency.\u00a0Overall FEP incidence was 11.73 per 100,000 person-years (95% CI 9.93-13.76) and was higher in males than in females (IRR=1.72, 95% CI 1.24-2.39), peaking in the 20-24-year age group.\u00a0Cannabis use was reported by 46.7% of cases, particularly frequent (weekly\/daily) use among young males. Higher cannabis-use frequency was associated with higher FEP incidence (IRR=1.73, 95% CI 1.49-2.01).\u00a0Post-pandemic FEP incidence exceeded pre-pandemic rates (IRR=2.01, 95% CI 1.29-3.13). This period effect attenuated and the 95% CI included 1.0 after adjustment for cannabis use (IRR=1.37, 95% CI 0.86-2.19).\u00a0FEP incidence in Porto varied across COVID-19 pandemic periods, and the post-pandemic increase may be partly related to cannabis exposure, underscoring prevention and early-intervention needs for young people who use cannabis.<\/jats:p>","DOI":"10.2139\/ssrn.6228347","type":"posted-content","created":{"date-parts":[[2026,3,6]],"date-time":"2026-03-06T14:41:08Z","timestamp":1772808068000},"source":"Crossref","is-referenced-by-count":0,"title":["First-Episode Psychosis incidence and cannabis-use patterns in Porto, 2018-2024: the impact of the COVID-19 pandemic"],"prefix":"10.2139","author":[{"ORCID":"https:\/\/orcid.org\/0009-0007-3695-8607","authenticated-orcid":true,"given":"Andrea","family":"Quattrone","sequence":"first","affiliation":[]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9261-6253","authenticated-orcid":true,"given":"Eleni","family":"Petkari","sequence":"additional","affiliation":[]},{"given":"Pedro Afonso  E.","family":"Costa Toipa","sequence":"additional","affiliation":[]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2675-5519","authenticated-orcid":true,"given":"YIFEI","family":"LANG","sequence":"additional","affiliation":[]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6098-429X","authenticated-orcid":true,"given":"Manuel  Gon\u00e7alves","family":"Pinho","sequence":"additional","affiliation":[]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6051-8309","authenticated-orcid":true,"given":"Diego","family":"Quattrone","sequence":"additional","affiliation":[]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0829-0519","authenticated-orcid":true,"given":"Robin","family":"Murray","sequence":"additional","affiliation":[]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5589-2147","authenticated-orcid":true,"given":"Celeste","family":"Silveira","sequence":"additional","affiliation":[]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5966-5723","authenticated-orcid":true,"given":"Mariana","family":"Pinto da Costa","sequence":"additional","affiliation":[]}],"member":"78","container-title":[],"original-title":[],"deposited":{"date-parts":[[2026,3,6]],"date-time":"2026-03-06T14:41:09Z","timestamp":1772808069000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.ssrn.com\/abstract=6228347"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026]]},"references-count":0,"URL":"https:\/\/doi.org\/10.2139\/ssrn.6228347","relation":{},"subject":[],"published":{"date-parts":[[2026]]},"subtype":"preprint"}}