{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,17]],"date-time":"2026-08-17T15:21:59Z","timestamp":1786980119595,"version":"build-2736575974"},"reference-count":28,"publisher":"Springer Science and Business Media LLC","issue":"2","license":[{"start":{"date-parts":[[2024,5,21]],"date-time":"2024-05-21T00:00:00Z","timestamp":1716249600000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0"},{"start":{"date-parts":[[2024,5,21]],"date-time":"2024-05-21T00:00:00Z","timestamp":1716249600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0"}],"funder":[{"DOI":"10.13039\/501100000780","name":"European Union","doi-asserted-by":"crossref","id":[{"id":"10.13039\/501100000780","id-type":"DOI","asserted-by":"crossref"}]}],"content-domain":{"domain":["link.springer.com"],"crossmark-restriction":false},"short-container-title":["Eur Arch Psychiatry Clin Neurosci"],"published-print":{"date-parts":[[2025,3]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>\n                    In Europe, concentrations of \u2206\n                    <jats:sup>9<\/jats:sup>\n                    -tetrahydrocannabinol (THC) in cannabis resin (also known as hash) have risen markedly in the past decade, potentially increasing risks of mental health disorders. Current approaches to international drug monitoring cannot distinguish between different types of cannabis resin which may have contrasting health effects due to THC and cannabidiol (CBD) content. Here, we compared concentrations of THC and CBD in different types of cannabis resin collected in Europe (either Moroccan-type, or Dutch-type). We then tested the ability of machine learning algorithms to classify the type of cannabis resin (either Moroccan-type, or Dutch-type) using routinely collected monitoring data on THC and CBD. Finally, we applied the optimal algorithm to new samples collected in countries where the type of cannabis resin was unknown, the UK and Denmark. Results showed that overall, Dutch-type samples had higher THC (Hedges\u2019 g\u2009=\u20092.39) and lower CBD (Hedges\u2019 g\u2009=\u20090.81) than Moroccan-type samples. A Support Vector Machine algorithm achieved classification accuracy exceeding 95%, with little variation in this estimate, good interpretability, and plausibility. It made contrasting predictions about the type of cannabis resin collected in the UK (94% Moroccan-type; 6% Dutch-type) and Denmark (36% Moroccan-type; 64% Dutch-type). In conclusion, we provide proof-of-concept evidence for the potential of machine learning to inform international drug monitoring. Our findings should not be interpreted as objective confirmatory evidence but suggest that Dutch-type cannabis resin has higher THC concentrations than Moroccan-type cannabis resin, which may contribute to variation in drug markets and health outcomes for people who use cannabis in Europe.\n                  <\/jats:p>","DOI":"10.1007\/s00406-024-01816-w","type":"journal-article","created":{"date-parts":[[2024,5,21]],"date-time":"2024-05-21T11:04:16Z","timestamp":1716289456000},"page":"421-429","update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["Applying machine learning to international drug monitoring: classifying cannabis resin collected in Europe using cannabinoid concentrations"],"prefix":"10.1007","volume":"275","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-5667-507X","authenticated-orcid":false,"given":"Tom P.","family":"Freeman","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Edward","family":"Beeching","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sam","family":"Craft","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Marta","family":"Di Forti","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Giampietro","family":"Frison","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Christian","family":"Lindholst","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Pieter E.","family":"Oomen","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"David","family":"Potter","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sander","family":"Rigter","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kristine","family":"R\u00f8mer Thomsen","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Luca","family":"Zamengo","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Andrew","family":"Cunningham","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Teodora","family":"Groshkova","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Roumen","family":"Sedefov","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"297","published-online":{"date-parts":[[2024,5,21]]},"reference":[{"key":"1816_CR1","volume-title":"Eu drug markets report 2019","author":"EMCDDA-Europol","year":"2019","unstructured":"EMCDDA-Europol (2019) Eu drug markets report 2019. Publications Office of the European Union, Luxembourg"},{"key":"1816_CR2","doi-asserted-by":"crossref","first-page":"1015","DOI":"10.1111\/add.14525","volume":"114","author":"TP Freeman","year":"2019","unstructured":"Freeman TP, Groshkova T, Cunningham A, Sedefov R, Griffiths P, Lynskey MT (2019) Increasing potency and price of cannabis in Europe, 2006\u201316. Addiction 114:1015\u20131023","journal-title":"Addiction"},{"key":"1816_CR3","doi-asserted-by":"crossref","first-page":"100227","DOI":"10.1016\/j.lanepe.2021.100227","volume":"10","author":"J Manthey","year":"2021","unstructured":"Manthey J, Freeman TP, Kilian C, L\u00f3pez-Pelayo H, Rehm J (2021) Public health monitoring of cannabis use in Europe: prevalence of use, cannabis potency, and treatment rates. Lancet Reg Health-Europe 10:100227","journal-title":"Lancet Reg Health-Europe"},{"key":"1816_CR4","doi-asserted-by":"crossref","first-page":"5","DOI":"10.1007\/s00406-019-00983-5","volume":"269","author":"S Chandra","year":"2019","unstructured":"Chandra S, Radwan MM, Majumdar CG, Church JC, Freeman TP, ElSohly MA (2019) New trends in cannabis potency in USA and europe during the last decade (2008\u20132017). Eur Arch Psychiatry Clin Neurosci 269:5\u201315","journal-title":"Eur Arch Psychiatry Clin Neurosci"},{"key":"1816_CR5","doi-asserted-by":"crossref","first-page":"72","DOI":"10.1016\/j.forsciint.2017.01.007","volume":"272","author":"L Dujourdy","year":"2017","unstructured":"Dujourdy L, Besacier F (2017) A study of cannabis potency in france over a 25 years period (1992\u20132016). Forensic Sci Int 272:72\u201380","journal-title":"Forensic Sci Int"},{"key":"1816_CR6","doi-asserted-by":"crossref","first-page":"110556","DOI":"10.1016\/j.forsciint.2020.110556","volume":"317","author":"L Zamengo","year":"2020","unstructured":"Zamengo L, Bettin C, Badocco D, Frison G (2020) Cannabis potency in north-east italy: a ten-year study (2010\u20132019). Forensic Sci Int 317:110556","journal-title":"Forensic Sci Int"},{"key":"1816_CR7","doi-asserted-by":"crossref","first-page":"402","DOI":"10.1037\/pha0000303","volume":"27","author":"K R\u00f8mer Thomsen","year":"2019","unstructured":"R\u00f8mer Thomsen K, Lindholst C, Thylstrup B, Kvamme S, Reitzel LA, Worm-Leonhard M, Englund A, Freeman TP, Hesse M (2019) Changes in the composition of cannabis from 2000\u20132017 in denmark: analysis of confiscated samples of cannabis resin. Exp Clin Psychopharmacol 27:402\u2013411","journal-title":"Exp Clin Psychopharmacol"},{"key":"1816_CR8","doi-asserted-by":"crossref","first-page":"736","DOI":"10.1016\/S2215-0366(22)00161-4","volume":"9","author":"K Petrilli","year":"2022","unstructured":"Petrilli K, Ofori S, Hines L, Taylor G, Adams S, Freeman TP (2022) Association of cannabis potency with mental ill health and addiction: a systematic review. Lancet Psychiatry 9:736\u2013750","journal-title":"Lancet Psychiatry"},{"key":"1816_CR9","doi-asserted-by":"crossref","first-page":"3181","DOI":"10.1017\/S0033291715001178","volume":"45","author":"T Freeman","year":"2015","unstructured":"Freeman T, Winstock A (2015) Examining the profile of high-potency cannabis and its association with severity of cannabis dependence. Psychol Med 45:3181\u20133189","journal-title":"Psychol Med"},{"key":"1816_CR10","doi-asserted-by":"crossref","first-page":"1044","DOI":"10.1001\/jamapsychiatry.2020.1035","volume":"77","author":"LA Hines","year":"2020","unstructured":"Hines LA, Freeman TP, Gage SH, Zammit S, Hickman M, Cannon M, Munafo M, MacLeod J, Heron J (2020) Association of high-potency cannabis use with mental health and substance use in adolescence. JAMA Psychiat 77:1044\u20131051","journal-title":"JAMA Psychiat"},{"key":"1816_CR11","doi-asserted-by":"crossref","first-page":"233","DOI":"10.1016\/S2215-0366(14)00117-5","volume":"2","author":"M Di Forti","year":"2015","unstructured":"Di Forti M, Marconi A, Carra E, Fraietta S, Trotta A, Bonomo M, Bianconi F, Gardner-Sood P, O\u2019Connor J, Russo M (2015) Proportion of patients in south london with first-episode psychosis attributable to use of high potency cannabis: a case-control study. Lancet Psychiatry 2:233\u2013238","journal-title":"Lancet Psychiatry"},{"key":"1816_CR12","doi-asserted-by":"crossref","first-page":"427","DOI":"10.1016\/S2215-0366(19)30048-3","volume":"6","author":"M Di Forti","year":"2019","unstructured":"Di Forti M, Quattrone D, Freeman TP, Tripoli G, Gayer-Anderson C, Quigley H, Rodriguez V, Jongsma HE, Ferraro L, La Cascia C (2019) The contribution of cannabis use to variation in the incidence of psychotic disorder across europe (eu-gei): a multicentre case-control study. Lancet Psychiatry 6:427\u2013436","journal-title":"Lancet Psychiatry"},{"key":"1816_CR13","doi-asserted-by":"crossref","first-page":"416","DOI":"10.1016\/j.drugpo.2014.01.001","volume":"25","author":"P-A Chouvy","year":"2014","unstructured":"Chouvy P-A, Afsahi K (2014) Hashish revival in morocco. Int J Drug Policy 25:416\u2013423","journal-title":"Int J Drug Policy"},{"key":"1816_CR14","doi-asserted-by":"crossref","first-page":"146","DOI":"10.1016\/j.toxac.2015.11.001","volume":"28","author":"H Stambouli","year":"2016","unstructured":"Stambouli H, El Bouri A, Bouayoun T (2016) \u00c9volution de la teneur en \u03b49-thc dans les saisies de r\u00e9sines de cannabis au maroc de 2005 \u00e0 2014. Toxicologie Analytique et Clinique 28:146\u2013152","journal-title":"Toxicologie Analytique et Clinique"},{"key":"1816_CR15","unstructured":"EMCDDA (2019) Developments in the european cannabis market, emcdda papers. Publications office of the european union, luxembourg"},{"key":"1816_CR16","doi-asserted-by":"crossref","first-page":"171","DOI":"10.1080\/13556210500123217","volume":"10","author":"F Pijlman","year":"2005","unstructured":"Pijlman F, Rigter S, Hoek J, Goldschmidt H, Niesink R (2005) Strong increase in total delta-THC in cannabis preparations sold in dutch coffee shops. Addict Biol 10:171\u2013180","journal-title":"Addict Biol"},{"key":"1816_CR17","volume-title":"Cannabis horticulture","author":"DJ Potter","year":"2014","unstructured":"Potter DJ (2014) Cannabis horticulture. Oxford University Press, Oxford"},{"key":"1816_CR18","doi-asserted-by":"crossref","first-page":"696","DOI":"10.1016\/j.neubiorev.2019.09.036","volume":"107","author":"AM Freeman","year":"2019","unstructured":"Freeman AM, Petrilli K, Lees R, Hindocha C, Mokrysz C, Curran HV, Saunders R, Freeman TP (2019) How does cannabidiol (cbd) influence the acute effects of delta-9-tetrahydrocannabinol (thc) in humans? A systematic review. Neurosci Biobehav Rev 107:696\u2013712","journal-title":"Neurosci Biobehav Rev"},{"key":"1816_CR19","doi-asserted-by":"crossref","first-page":"182","DOI":"10.1080\/07929978.2016.1177983","volume":"63","author":"LO Hanu\u0161","year":"2016","unstructured":"Hanu\u0161 LO, Levy R, De La Vega D, Katz L, Roman M, Tom\u00ed\u010dek P (2016) The main cannabinoids content in hashish samples seized in Israel and Czech Republic. Israel J Plant Sci 63:182\u2013190","journal-title":"Israel J Plant Sci"},{"key":"1816_CR20","doi-asserted-by":"crossref","first-page":"1941","DOI":"10.1111\/add.13082","volume":"110","author":"RJ Niesink","year":"2015","unstructured":"Niesink RJ, Rigter S, Koeter MW, Brunt TM (2015) Potency trends of \u03b49-tetrahydrocannabinol, cannabidiol and cannabinol in cannabis in the netherlands: 2005\u201315. Addiction 110:1941\u20131950","journal-title":"Addiction"},{"key":"1816_CR21","doi-asserted-by":"crossref","first-page":"41","DOI":"10.1007\/s10994-010-5221-8","volume":"85","author":"H-F Yu","year":"2011","unstructured":"Yu H-F, Huang F-L, Lin C-J (2011) Dual coordinate descent methods for logistic regression and maximum entropy models. Mach Learn 85:41\u201375","journal-title":"Mach Learn"},{"key":"1816_CR22","doi-asserted-by":"crossref","first-page":"218","DOI":"10.21037\/atm.2016.03.37","volume":"4","author":"Z Zhang","year":"2016","unstructured":"Zhang Z (2016) Introduction to machine learning: K-nearest neighbors. Ann Transl Med 4:218","journal-title":"Ann Transl Med"},{"key":"1816_CR23","doi-asserted-by":"crossref","DOI":"10.1201\/9781315139470","volume-title":"Classification and regression trees","author":"L Breiman","year":"2017","unstructured":"Breiman L, Friedman JH, Olshen RA, Stone CJ (2017) Classification and regression trees. Routledge, London"},{"key":"1816_CR24","doi-asserted-by":"crossref","first-page":"5","DOI":"10.1023\/A:1010933404324","volume":"45","author":"L Breiman","year":"2001","unstructured":"Breiman L (2001) Random forests. Mach Learn 45:5\u201332","journal-title":"Mach Learn"},{"key":"1816_CR25","doi-asserted-by":"crossref","first-page":"1565","DOI":"10.1038\/nbt1206-1565","volume":"24","author":"WS Noble","year":"2006","unstructured":"Noble WS (2006) What is a support vector machine? Nat Biotechnol 24:1565\u20131567","journal-title":"Nat Biotechnol"},{"key":"1816_CR26","first-page":"3","volume":"1","author":"H Zhang","year":"2004","unstructured":"Zhang H (2004) The optimality of naive bayes. A A 1:3","journal-title":"A A"},{"key":"1816_CR27","doi-asserted-by":"crossref","first-page":"532","DOI":"10.1007\/978-0-387-39940-9_565","volume-title":"Encyclopedia of database systems","author":"P Refaeilzadeh","year":"2009","unstructured":"Refaeilzadeh P, Tang L, Liu H (2009) Cross-validation. In: Liu L, \u00d6zsu MT (eds) Encyclopedia of database systems. Springer, Boston, pp 532\u2013538"},{"key":"1816_CR28","doi-asserted-by":"crossref","first-page":"628","DOI":"10.1002\/dta.2368","volume":"10","author":"DJ Potter","year":"2018","unstructured":"Potter DJ, Hammond K, Tuffnell S, Walker C, Di Forti M (2018) Potency of \u03b49\u2013tetrahydrocannabinol and other cannabinoids in cannabis in england in 2016: implications for public health and pharmacology. Drug Test Anal 10:628\u2013635","journal-title":"Drug Test Anal"}],"container-title":["European Archives of Psychiatry and Clinical Neuroscience"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/link.springer.com\/content\/pdf\/10.1007\/s00406-024-01816-w.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/link.springer.com\/article\/10.1007\/s00406-024-01816-w\/fulltext.html","content-type":"text\/html","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/link.springer.com\/content\/pdf\/10.1007\/s00406-024-01816-w.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,3,27]],"date-time":"2025-03-27T16:05:20Z","timestamp":1743091520000},"score":1,"resource":{"primary":{"URL":"https:\/\/link.springer.com\/10.1007\/s00406-024-01816-w"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2024,5,21]]},"references-count":28,"journal-issue":{"issue":"2","published-print":{"date-parts":[[2025,3]]}},"alternative-id":["1816"],"URL":"https:\/\/doi.org\/10.1007\/s00406-024-01816-w","relation":{},"ISSN":["0940-1334","1433-8491"],"issn-type":[{"value":"0940-1334","type":"print"},{"value":"1433-8491","type":"electronic"}],"subject":[],"published":{"date-parts":[[2024,5,21]]},"assertion":[{"value":"31 October 2023","order":1,"name":"received","label":"Received","group":{"name":"ArticleHistory","label":"Article History"}},{"value":"19 April 2024","order":2,"name":"accepted","label":"Accepted","group":{"name":"ArticleHistory","label":"Article History"}},{"value":"21 May 2024","order":3,"name":"first_online","label":"First Online","group":{"name":"ArticleHistory","label":"Article History"}},{"order":1,"name":"Ethics","group":{"name":"EthicsHeading","label":"Declarations"}},{"value":"The authors declare that they have no conflict of interest.","order":2,"name":"Ethics","group":{"name":"EthicsHeading","label":"Conflict of interest"}}]}}