{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,3]],"date-time":"2026-09-03T03:43:07Z","timestamp":1788406987516,"version":"build-2803163510"},"reference-count":48,"publisher":"Cambridge University Press (CUP)","license":[{"start":{"date-parts":[[2026,5,4]],"date-time":"2026-05-04T00:00:00Z","timestamp":1777852800000},"content-version":"unspecified","delay-in-days":123,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0"}],"funder":[{"DOI":"10.13039\/501100000265","name":"Medical Research Council","doi-asserted-by":"publisher","award":["MR\/Y017560\/1"],"award-info":[{"award-number":["MR\/Y017560\/1"]}],"id":[{"id":"10.13039\/501100000265","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["cambridge.org"],"crossmark-restriction":true},"short-container-title":["Psychol. Med."],"published-print":{"date-parts":[[2026]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:sec id=\"S0033291726104036_sec1\">\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>In recent decades, the potency of cannabis resin increased globally, raising concerns, as higher potency has been associated with increased risk of psychiatric harms at the individual level. The aim here was to examine whether changes over time in the potency of seized cannabis resin samples were associated with psychiatric harms at the population level.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"S0033291726104036_sec2\" sec-type=\"methods\">\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>Data on \u2206-9-tetrahydrocannabinol (THC) concentration in seized cannabis resin were obtained from forensic departments in Denmark (2000\u20132022), the country reporting the highest potency in Europe. Data on admissions to cannabis treatment, incidence of cannabis-induced psychosis, and dual diagnosis (schizophrenia and cannabis use disorder) were obtained from national registers. Time-dependent associations between potency and the outcomes were examined with mixed-effects linear regression models and associations across age and sex were explored. Candidate time lags were 0\u201310\u00a0years.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"S0033291726104036_sec3\" sec-type=\"results\">\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      THC concentration increased almost fourfold: mean 8.3\u201331.2% from 2000 to 2022. In fully adjusted models, THC was positively associated with first-time cannabis treatment entry at lags of 0\u20136, strongest at year 0 (\n                      <jats:italic>p\u00a0&lt;<\/jats:italic>\n                      \u00a00.0001); incidence of cannabis-induced psychosis at lags of 0\u20134, strongest at year 0 (\n                      <jats:italic>p<\/jats:italic>\n                      \u00a0&lt;\u00a00.0001); and incidence of dual diagnosis at lags of 0\u20131, strongest at year 0 (\n                      <jats:italic>p\u00a0&lt;<\/jats:italic>\n                      \u00a00.01). No positive associations were found in unadjusted models. Subgroup analyses indicated associations in older patients and women.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"S0033291726104036_sec4\" sec-type=\"conclusions\">\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>Potency of seized cannabis resin increased almost fourfold from 2000 to 2022. Changes in cannabis potency were positively associated with psychiatric harms at the population level across all outcomes.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1017\/s0033291726104036","type":"journal-article","created":{"date-parts":[[2026,5,4]],"date-time":"2026-05-04T06:41:10Z","timestamp":1777876870000},"update-policy":"https:\/\/doi.org\/10.1017\/policypage","source":"Crossref","is-referenced-by-count":2,"title":["Changes in cannabis potency and cannabis-related psychiatric harms: a 23-year ecological study in Denmark"],"prefix":"10.1017","volume":"56","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-3612-5529","authenticated-orcid":false,"given":"Kristine","family":"R\u00f8mer Thomsen","sequence":"first","affiliation":[{"id":[{"id":"https:\/\/ror.org\/01aj84f44","id-type":"ROR","asserted-by":"publisher"}],"name":"Aarhus University"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Birgitte","family":"Thylstrup","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/01aj84f44","id-type":"ROR","asserted-by":"publisher"}],"name":"Aarhus University"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Morten","family":"Hesse","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/01aj84f44","id-type":"ROR","asserted-by":"publisher"}],"name":"Aarhus University"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7293-1611","authenticated-orcid":false,"given":"Christian","family":"Lindholst","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/01aj84f44","id-type":"ROR","asserted-by":"publisher"}],"name":"Aarhus University"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0181-6274","authenticated-orcid":false,"given":"Lotte Ask","family":"Reitzel","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/035b05819","id-type":"ROR","asserted-by":"publisher"}],"name":"University of Copenhagen"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Tina Stokholm","family":"Eriksen","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/03yrrjy16","id-type":"ROR","asserted-by":"publisher"}],"name":"University of Southern Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3475-0558","authenticated-orcid":false,"given":"Annette","family":"Erlangsen","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/047m0fb88","id-type":"ROR","asserted-by":"publisher"}],"name":"Mental health services in the Capital Region of Denmark"},{"id":[{"id":"https:\/\/ror.org\/00za53h95","id-type":"ROR","asserted-by":"publisher"}],"name":"Johns Hopkins Bloomberg School of Public Health"},{"id":[{"id":"https:\/\/ror.org\/019wvm592","id-type":"ROR","asserted-by":"publisher"}],"name":"The Australian National University"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2478-209X","authenticated-orcid":false,"given":"Amir","family":"Englund","sequence":"additional","affiliation":[{"name":"King\u2019s College London"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5667-507X","authenticated-orcid":false,"given":"Tom P.","family":"Freeman","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/002h8g185","id-type":"ROR","asserted-by":"publisher"}],"name":"University of Bath"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Carsten","family":"Hjorth\u00f8j","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/047m0fb88","id-type":"ROR","asserted-by":"publisher"}],"name":"Mental health services in the Capital Region of Denmark"},{"id":[{"id":"https:\/\/ror.org\/035b05819","id-type":"ROR","asserted-by":"publisher"}],"name":"University of Copenhagen"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"56","published-online":{"date-parts":[[2026,5,4]]},"reference":[{"key":"S0033291726104036_r45","doi-asserted-by":"publisher","DOI":"10.1007\/s10654-020-00703-7"},{"key":"S0033291726104036_r10","unstructured":"Danish Health Authority. 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Cannabis \u2013 the current situation in Europe (European Drug Report 2025)."},{"key":"S0033291726104036_r24","doi-asserted-by":"publisher","DOI":"10.1016\/j.psychres.2023.115626"}],"container-title":["Psychological Medicine"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.cambridge.org\/core\/services\/aop-cambridge-core\/content\/view\/S0033291726104036","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,5,4]],"date-time":"2026-05-04T06:41:17Z","timestamp":1777876877000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.cambridge.org\/core\/product\/identifier\/S0033291726104036\/type\/journal_article"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026]]},"references-count":48,"alternative-id":["S0033291726104036"],"URL":"https:\/\/doi.org\/10.1017\/s0033291726104036","relation":{},"ISSN":["0033-2917","1469-8978"],"issn-type":[{"value":"0033-2917","type":"print"},{"value":"1469-8978","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026]]},"assertion":[{"value":"\u00a9 The Author(s), 2026. 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