Systematic review of adolescent cannabis use links elevated addiction risk and neurodevelopmental concerns compared to adult onset.
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Key Takeaway
Note elevated addiction risk and mixed cognitive findings in adolescent cannabis use versus adult onset.
This systematic review evaluates the neurodevelopmental consequences of adolescent cannabis use compared to adult-onset use, drawing on data from 8,432 participants in longitudinal studies. The scope covers structural brain changes, cognitive impacts, addiction vulnerability, and long-term outcomes such as educational difficulties and mental health problems.
Key synthesized findings indicate dose-dependent alterations in brain structure, including reduced prefrontal cortical and hippocampal/amygdala volumes, accelerated cortical thinning, and impaired white matter connectivity. Regarding addiction risk, the review reports odds ratios of 3.9–7.2 for adolescents versus adults. Cognitive effects showed mixed findings, with some studies indicating persistent deficits after prolonged abstinence while others found no effects after controlling for confounders.
The authors note significant limitations, including heterogeneous definitions, confounders, and the inherent constraints of observational designs that prevent clear causal inference. Consequently, the certainty of causal relationships remains unclear, and methodological limitations restrict the ability to draw firm conclusions about direct causation.
Despite these constraints, the practice relevance is that findings support age-specific prevention and specialized interventions. Clinicians should interpret these results cautiously, recognizing that the evidence does not establish definitive causal links but rather highlights associations requiring further investigation.
View Original Abstract ↓
Background and hypothesisCannabis use initiation during adolescence has increased globally, raising concerns about neurodevelopmental consequences during this critical period when the brain undergoes extensive remodeling in cannabinoid receptor-rich regions.Study designThis systematic review examines neurodevelopmental consequences of adolescent cannabis use, focusing on structural brain changes, cognitive impacts, addiction vulnerability, and long-term outcomes. We searched PubMed, EMBASE, PsycINFO, and Web of Science (2000-2025) for studies examining cannabis effects in adolescent populations. Following PRISMA guidelines, two reviewers screened 3,421 records and assessed 156 full-text articles, including studies with neuroimaging, cognitive assessments, or longitudinal follow-up.Study resultsThirty-six studies involving 8,432 participants met criteria: 23 longitudinal cohorts (62.2%), 8 cross-sectional (22.2%), 4 RCTs (11.1%), and 1 case-control study (2.8%). Neuroimaging revealed dose-dependent alterations including reduced prefrontal cortical and hippocampal/amygdala volumes, accelerated cortical thinning in longitudinal studies, and impaired white matter connectivity correlating with initiation age. Cognitive findings were mixed — some showed persistent deficits after prolonged abstinence in adolescent-onset users, others found no effects after controlling for confounders. Epidemiological studies consistently showed elevated addiction risk (ORs 3.9–7.2) in adolescents versus adults. Long-term associations included educational difficulties, mental health problems, and functional impairment, though causal relationships remained unclear.ConclusionsAdolescent cannabis use associates with structural brain changes, elevated addiction risk, and variable cognitive effects, suggesting greater vulnerability versus adult-onset use. However, methodological limitations including confounders, heterogeneous definitions, and observational designs limit causal inference. Findings support age-specific prevention and specialized interventions while highlighting needs for rigorous longitudinal research establishing causality.Systematic review registrationhttps://www.crd.york.ac.uk/prospero/, identifierCRD420251165329.
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