Changes in Symptoms of Cannabis Use Disorder of Ontario Youth Across the COVID-19 Pandemic: A Longitudinal Cohort Study.

Berryhill J.; Colman I.; Imtiaz S.; Chaiton M.; Wells S.; Rueda S.; Tadrous M.; Hamilton H.; Schwartz R.; Elton-Marshall T. · Substance use & addiction journal · 2026

**Background & Methods** This longitudinal cohort study examined 1,579 Ontario youth (mean age 22 years; 55% female) aged 16-30 who reported cannabis use in the past 3 months. Participants completed online questionnaires in 2022 and 2023 assessing cannabis use patterns and symptoms of cannabis use disorder (CUD) using the Cannabis Use Disorder Identification Test-Revised (CUDIT-R), with linear regression models adjusted for sociodemographic factors and psychological distress. **Key Findings** • Increased cannabis use during the COVID-19 pandemic was significantly associated with higher CUDIT-R scores (β: 1.49; 95% CI: 0.99, 2.00), indicating worsening CUD symptoms across the survey period. • The association between pandemic-related increased cannabis use and CUD symptom changes was significantly stronger in younger participants compared to older participants (P = .04), suggesting age-related vulnerability. • CUD symptoms remained elevated approximately 3 years after the initial COVID-19 declaration, indicating persistent pandemic-related impacts on problematic cannabis use among youth. **Dosage & Administration** Not reported. **Safety & Adverse Effects** Not reported. The study focused on measuring CUD symptom severity rather than documenting specific adverse effects. However, the research emphasizes that problematic cannabis use in young adults is associated with impaired neurodevelopment and adverse health outcomes. **Evidence Quality** This longitudinal cohort study provides moderate evidence with several limitations. The sample was restricted to Ontario residents and active cannabis users in the past 3 months, limiting generalizability to non-users or other geographic populations. Self-reported data on cannabis use is subject to recall and social desirability bias. The study lacks a control group of non-users and does not establish causality—increased use during the pandemic may reflect confounding factors such as underlying mental health conditions rather than direct pandemic effects. The 2-year follow-up period (2022-2023) represents a reasonable timeframe for assessing longitudinal changes. Strengths include the relatively large sample size, use of a validated screening instrument (CUDIT-R), and adjustment for psychological distress. The finding of age-related differences strengthens the analysis but requires replication in diverse populations to confirm.

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