SynthesisPsychological medicine2021
Intelligence quotient decline following frequent or dependent cannabis use in youth: a systematic review and meta-analysis of longitudinal studies.
Synthesis in Psychological medicine, 2021. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 16 papers, 1 of them a synthesis that pooled it.
What it found
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The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
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Who cites it
16 citing papers in PubMed, 1 synthesis or guideline pooled it.
- Balancing risks and benefits of cannabis use: umbrella review of meta-analyses of randomised controlled trials and observational studies.BMJ (Clinical research ed.) · 2023Pooled it
- Patterns, motivations, and healthcare experiences of medical cannabis use among gender and sexuality diverse people in Australia: findings from the Cannabis as Medicine Survey 2022 (CAMS-22).Harm reduction journal · 2026Article
- Polysubstance use in adolescents: conceptual issues and the need for a new public health framework and approach.Psychological medicine · 2026Article
- The longitudinal association between adverse childhood experiences and persistence of psychotic-like experiences in young people: evidence from the ALSPAC birth cohort.Psychological medicine · 2026Article
- How does cognition change over time in young people who use cannabis recreationally? A narrative review of the longitudinal literature to date.Psychopharmacology · 2026Review
- Cannabis, cannabinoids and health: a review of evidence on risks and medical benefits.European archives of psychiatry and clinical neuroscience · 2025Review
- Prenatal cannabis exposure, the brain, and psychopathology during early adolescence.Nature. Mental health · 2024Article
- Priming lymphocyte responsiveness and differential T cell signaling in pediatric IBD patients withbioRxiv : the preprint server for biology · 2024Article
- Cannabis Use and Its Impact on Mental Health in Youth in Australia and the United States: A Scoping Review.Epidemiologia (Basel, Switzerland) · 2024Article
- Daily ΔBiological psychiatry global open science · 2023Article
- Multilevel Risk and Protective Factors for Frequent and Nonfrequent Past-30-Day Marijuana Use: Findings From a Representative Sample of High School Youth.Journal of studies on alcohol and drugs · 2023Article
- Nasal accumulation and metabolism of ΔPharmacological research · 2023Article
- DNA methylation changes associated with cannabis use and verbal learning performance in adolescents: an exploratory whole genome methylation study.Translational psychiatry · 2022Article
- Cognitive Profiles of Adolescent Inpatients with Substance Use Disorder.Children (Basel, Switzerland) · 2022Article
- The Neurocognitive Effects of Cannabis Across the Lifespan.Current behavioral neuroscience reports · 2021Article
- Adolescent Substance Abuse, Transgenerational Consequences and Epigenetics.Current neuropharmacology · 2021Article
Corrections and comments
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Authors and funding
6 authors.
Funding
No grant is acknowledged in the PubMed record.
Abstract
Previous systematic reviews and meta-analyses of cross-sectional data assessing the effect of cannabis on cognitive functioning and intelligence show inconsistent results. We hypothesized that frequent and dependent cannabis use in youth would be associated with Intelligence Quotient (IQ) decline. This study is a systematic review and meta-analysis. We searched Embase, PubMed and PsychInfo from inception to 24 January 2020. We included studies with non-treatment seeking samples and pre- and post-exposure measures of IQ. We requested data from authors if summary data was not available from published work. We preregistered our review with PROSPERO (ID no. CRD42019125624). We found seven cohort studies including 808 cases and 5308 controls. We found a significant effect for the association between frequent or dependent cannabis use in youth and IQ change, Cohen's d = -0.132 (95% CI -0.198 to -0.066) p < 0.001. Statistical heterogeneity between studies was also low at I2 = 0.2%. Study quality was moderate to high. This translates to an average decline of approximately 2 IQ points following exposure to cannabis in youth. Future studies should have longer periods of follow up to assess the magnitude of developmental impact.
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Registered trials
Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.