Detecting Misconception Surges in Opioid Policy: A Zero-Shot LLM Analysis of British Columbia’s Decriminalization Pilot

Detecting Misconception Surges in Opioid Policy: A Zero-Shot LLM Analysis of British Columbia’s Decriminalization Pilot | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Detecting Misconception Surges in Opioid Policy: A Zero-Shot LLM Analysis of British Columbia’s Decriminalization Pilot Sepehr Harfi Moridani, Marwa Sharifi, Chan Pang Yang, Konrad Samsel, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8897658/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 9 You are reading this latest preprint version Abstract Background: In January 2023, British Columbia (BC) launched Canada's first drug decriminalization pilot in response to persistently high opioid-related deaths. This initiative removed criminal penalties for possession of up to 2.5 grams of certain illicit drugs to reduce stigma and increase service use. Social media platforms such as Reddit provide a real-time window into public perceptions and misconceptions about such policies. Methods: We collected 22,131 comments posted between January 2023 and October 2024 from subreddits discussing decriminalization in British Columbia. A zero-shot large language model applied a multi-label taxonomy with four misconception classes and one no-claim class. Expert adjudication of 547 comments with model disagreement supported selection of the primary classifier for analysis. We tracked monthly misconception prevalence and used subreddit-week reply premiums and lattice clustering to detect engagement bursts. Negative binomial models quantified reply differences across periods, regions, and comment-level harm reduction references. Results: GPT-4o labeled 4,473 comments as containing at least one misconception, and policy-target misinterpretation and impact claims dominated through early 2024. After the May 2024 amendment that restricted possession in public spaces, Legal-Status Confusion and Enforcement Misconceptions increased and peaked in June 2024. These comments received an 11% reply premium, with an incidence rate ratio of 1.11 (95% CI 1.02-1.21), and the premium increased after May 2024 (1.18, 1.16-1.21). Reply premiums clustered into four bursts from February to July 2024, and each burst lasted 2 to 5 weeks across 2 to 5 subreddits. Harm-reduction terms predicted higher replies, with an incidence rate ratio of 1.12 (95% CI 1.04-1.20), and the interaction ratio was 0.81 (0.66-0.98). Community-level harm-reduction visibility did not predict week-to-week variation in reply premiums for either misconception class. Conclusions: Public discussion of BC's decriminalization policy revealed persistent confusion, and legal and enforcement confusion intensified around the May 2024 revision. Burst detection on social platforms can identify when and where confusion concentrates, which supports timely public clarification and service signposting. During future amendments, concise messages about permissible locations and remaining police authority may reduce avoidable enforcement contact and misinformation. Decriminalization Drug policy Social listening policy misperceptions Harm reduction communication Large language models Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Reviews received at journal 08 May, 2026 Reviewers agreed at journal 08 May, 2026 Reviewers agreed at journal 01 May, 2026 Reviews received at journal 01 Apr, 2026 Reviewers agreed at journal 26 Mar, 2026 Reviewers invited by journal 24 Mar, 2026 Editor assigned by journal 20 Feb, 2026 Submission checks completed at journal 20 Feb, 2026 First submitted to journal 17 Feb, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8897658","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":611591467,"identity":"74a1cd91-f529-4001-a2cd-a85646180686","order_by":0,"name":"Sepehr Harfi Moridani","email":"","orcid":"","institution":"University of Toronto","correspondingAuthor":false,"prefix":"","firstName":"Sepehr","middleName":"Harfi","lastName":"Moridani","suffix":""},{"id":611591468,"identity":"173a18c2-7e9f-40e8-804a-fcc491078917","order_by":1,"name":"Marwa Sharifi","email":"","orcid":"","institution":"University of 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This initiative removed criminal penalties for possession of up to 2.5 grams of certain illicit drugs to reduce stigma and increase service use. Social media platforms such as Reddit provide a real-time window into public perceptions and misconceptions about such policies.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eMethods: We collected 22,131 comments posted between January 2023 and October 2024 from subreddits discussing decriminalization in British Columbia. A zero-shot large language model applied a multi-label taxonomy with four misconception classes and one no-claim class. Expert adjudication of 547 comments with model disagreement supported selection of the primary classifier for analysis. We tracked monthly misconception prevalence and used subreddit-week reply premiums and lattice clustering to detect engagement bursts. Negative binomial models quantified reply differences across periods, regions, and comment-level harm reduction references.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eResults: GPT-4o labeled 4,473 comments as containing at least one misconception, and policy-target misinterpretation and impact claims dominated through early 2024. After the May 2024 amendment that restricted possession in public spaces, Legal-Status Confusion and Enforcement Misconceptions increased and peaked in June 2024. These comments received an 11% reply premium, with an incidence rate ratio of 1.11 (95% CI 1.02-1.21), and the premium increased after May 2024 (1.18, 1.16-1.21). Reply premiums clustered into four bursts from February to July 2024, and each burst lasted 2 to 5 weeks across 2 to 5 subreddits. Harm-reduction terms predicted higher replies, with an incidence rate ratio of 1.12 (95% CI 1.04-1.20), and the interaction ratio was 0.81 (0.66-0.98). Community-level harm-reduction visibility did not predict week-to-week variation in reply premiums for either misconception class.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eConclusions: Public discussion of BC's decriminalization policy revealed persistent confusion, and legal and enforcement confusion intensified around the May 2024 revision. Burst detection on social platforms can identify when and where confusion concentrates, which supports timely public clarification and service signposting. During future amendments, concise messages about permissible locations and remaining police authority may reduce avoidable enforcement contact and misinformation.\u003c/p\u003e","manuscriptTitle":"Detecting Misconception Surges in Opioid Policy: A Zero-Shot LLM Analysis of British Columbia’s Decriminalization Pilot","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-26 06:22:06","doi":"10.21203/rs.3.rs-8897658/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorInvitedReview","content":"","date":"2026-05-08T18:14:29+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"282863652953414822564732181145655468944","date":"2026-05-08T16:46:40+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"134143931206924342330629795152418261639","date":"2026-05-01T16:50:45+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-01T09:49:47+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"66007637541217071688991240719558708410","date":"2026-03-26T09:45:12+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-03-24T12:55:35+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-02-20T09:02:11+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-02-20T09:00:32+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Public Health","date":"2026-02-17T05:15:21+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-public-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"pubh","sideBox":"Learn more about [BMC Public Health](http://bmcpublichealth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/pubh/default.aspx","title":"BMC Public Health","twitterHandle":"@BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"737a82be-c60a-4573-947d-8537a2c5dd4d","owner":[],"postedDate":"March 26th, 2026","published":true,"recentEditorialEvents":[{"type":"editorInvitedReview","content":"","date":"2026-05-08T18:14:29+00:00","index":91,"fulltext":""},{"type":"reviewerAgreed","content":"282863652953414822564732181145655468944","date":"2026-05-08T16:46:40+00:00","index":90,"fulltext":""},{"type":"reviewerAgreed","content":"134143931206924342330629795152418261639","date":"2026-05-01T16:50:45+00:00","index":88,"fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-03-26T06:22:06+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-26 06:22:06","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8897658","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8897658","identity":"rs-8897658","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}