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Cited by 68Cannabis and Cannabinoid ResearchSchizophrenia research and treatmentForensic Toxicology and Drug Analysis

Risk-thresholds for the association between frequency of cannabis use and the development of psychosis: a systematic review and meta-analysis

Open access
Robinson, Tessa, Ali, Muhammad Usman, Easterbrook, Bethany, Hall, Wayne, Jutras-Aswad, Didier, Fischer, Benedikt·2023·Psychological Medicine
DOI 10.1017/s0033291722000502PMC PMC10317818
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Abstract

Background: Epidemiological studies show a dose–response association between cannabis use and the risk of psychosis. This review aimed to determine whether there are identifiable risk-thresholds between the frequency of cannabis use and psychosis development. Methods: Systematic search of Embase, MEDLINE, PsycINFO, CINAHL, and Web of Science for relevant studies (1 January 2010–26 April 2021). Case–control or cohort studies that investigated the relationship between cannabis use and the risk of psychosis development that reported effect estimates [odds ratios (OR), hazard ratios (HR), risk ratios (RR)] or the raw data to calculate them, with information on the frequency of cannabis consumption were included. Effect estimates were extracted from individual studies and converted to RR. Two-stage dose–response multivariable meta-analytic models were utilized and sensitivity analyses conducted. The Newcastle Ottawa Scale was used to assess the risk of bias of included studies. Results: Ten original (three cohorts, seven case–control) studies were included, including 7390 participants with an age range of 12–65 years. Random-effect model meta-analyses showed a significant log-linear dose–response association between cannabis use frequency and psychosis development. A restricted cubic-splines model provided the best fit for the data, with the risk of psychosis significantly increasing for weekly or more frequent cannabis use [RR = 1.01, 95% confidence interval (CI) 0.93–1.11 yearly; RR = 1.10, 95% CI 0.97–1.25 monthly; RR = 1.35, 95% CI 1.19–1.52 weekly; RR = 1.76, 95% CI 1.47–2.12 daily] Conclusion: Individuals using cannabis frequently are at increased risk of psychosis, with no significant risk associated with less frequent use. Public health prevention messages should convey these risk-thresholds, which should be refined through further work.

AI snapshot

Written from the paper’s full text.

TL;DR

This systematic review and meta-analysis found a dose–response association between cannabis use frequency and psychosis development, with risk significantly elevated only at weekly or more frequent use. The best-fitting restricted cubic-splines model showed no significant increase for yearly or monthly use, but a 35% increase for weekly use and a 76% increase for daily/near-daily use compared with never use.

Key findings

  • Ten studies (three cohort, seven case–control) including 7,390 participants aged 12–65 years were meta-analyzed.
  • Random-effects meta-analysis showed a significant log-linear dose–response association between cannabis use frequency and psychosis development (p < 0.0001); each category increase was associated with a 1.15-times (14.7%; 95% CI 9.8%–19.8%) increase in risk.
  • The restricted cubic-splines model provided the best fit: yearly use RR = 1.01 (95% CI 0.93–1.11), monthly use RR = 1.10 (95% CI 0.97–1.25), weekly use RR = 1.35 (95% CI 1.19–1.52), and daily/near-daily use RR = 1.76 (95% CI 1.47–2.12), relative to never use.
  • Heterogeneity was significant (I² = 87.2%; p < 0.001), and certainty-in-findings was rated moderate using GRADE.

Methods

  • Systematic review and meta-analysis conducted per PRISMA 2020 and registered with PROSPERO (#CRD42021234708); searches covered Embase, MEDLINE, PsycINFO, CINAHL, and Web of Science from 1 January 2010 to 26 April 2021.
  • Included case–control or cohort studies investigating cannabis use and psychosis development, with effect estimates (OR, HR, RR) or raw data, and quantified frequency information allowing at least three frequency categories (monthly, weekly, daily/near-daily).
  • Effect estimates were converted to RRs; two-stage dose–response multivariable meta-analytic models with random-effects modeling were used, plus sensitivity analyses using quadratic and restricted cubic-splines models; risk of bias was assessed with the Newcastle Ottawa Scale.

Limitations

  • Stated: most included studies did not report potential contributor factors such as cannabis potency, and half did not control for or had unclear control of co-use of alcohol, tobacco, or other recreational substances.
  • Stated: all included studies used self-report measures of cannabis use frequency, which may be prone to recall bias; categorization may lose information by treating within-category participants as equal in risk; risk-thresholds were limited to a-priori defined frequency categories; design differences limited subgroup analyses; and all studies were observational, lowering overall quality and increasing potential risk of bias versus randomized trials.
  • Evident from the text: heterogeneity was high (I² = 87.2%), and funnel plot assessment showed some asymmetry, though the counter-enhanced funnel plot did not indicate missing studies in areas of low statistical significance.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1017/s0033291722000502

Cites

79 of 79 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 58 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    The random-effect model showed a significant log-linear dose-response association between frequency of cannabis use and risk of psychosis development (p < 0.0001).

    “Random-effect model meta-analyses showed a significant log-linear dose–response association between cannabis use frequency and psychosis development.”
    • Also stated in: § Random effect model · plain
      “The REM showed a significant log-linear dose–response association between the frequency of cannabis use category and risk of psychosis development (p < 0.0001).”
    Quote in the paperSubstantial claim
  • Findingown data

    In the restricted cubic-splines model, weekly cannabis use was associated with a significant increase in risk of psychosis compared with never use (RR = 1.35, 95% CI 1.19-1.52).

    “RR = 1.35, 95% CI 1.19–1.52 weekly”
    • Also stated in: § Sensitivity analysis · plain
      “RR:1.35 (95% CI 1.19–1.52) for ‘weekly’”
    Quote in the paperSubstantial claim
  • Findingown data

    Ten original studies (three cohort and seven case-control) were included in the review.

    “Ten original (three cohorts, seven case–control) studies were included”
    • Also stated in: § Study selection (see Fig. 1) · plain
      “A total of ten original studies (three cohort and seven case–control studies) were included in this review”
    Quote in the paperSubstantial claim
  • Findingown data

    There was significant heterogeneity among studies (I2 = 87.2%; p < 0.001).

    “displaying significant heterogeneity (I2 = 87.2%; p < 0.001).”
    Quote in the paperSubstantial claim
  • Findingown data

    In the restricted cubic-splines model, yearly cannabis use was not associated with a significant increase in risk of psychosis compared with never use (RR = 1.01, 95% CI 0.93-1.11).

    “RR = 1.01, 95% confidence interval (CI) 0.93–1.11 yearly”
    • Also stated in: § Sensitivity analysis · plain
      “the risk of psychosis increased from RR:1.01 (95% CI 0.93–1.11) for ‘yearly’”
    Quote in the paperNot a substantial claim
  • May combine two claims. 15
  • Classified as probably not a substantial claim. 28

  • May combine two claims.

    Findingown data

    There was some funnel plot asymmetry when assessing publication bias, but the majority of estimates were clustered around the summary-effect-estimate.

    “There was some funnel plot asymmetry when assessing publication bias, but the majority of estimates were clustered around the summary-effect-estimate.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Findingown data

    The included studies comprised 7390 participants with an age range of 12-65 years.

    “including 7390 participants with an age range of 12–65 years”
    • Also stated in: § Study characteristics (see Table 1) · plain
      “Studies included a total of 7390 participants ranging in age from 12 to 65 years.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    A large proportion of the variance was explained by within-study differences (86.67%), with between-study variance contributing 0.56% of heterogeneity.

    “A large proportion of the variance was explained by within-study-differences (86.67%), with between-study variance contributing to 0.56% of heterogeneity”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The review's findings indicate that the risk of psychosis is significantly elevated for frequent cannabis use, defined as at least weekly, and is significantly clearest for weekly or higher patterns of use.

    “our findings suggest that such a risk is significantly clearest for more frequent – i.e., ‘weekly’ or higher – patterns of cannabis use”
    • Also stated in: § Discussion · hedged
      “While more frequent cannabis use to be appears associated with an elevated risk of psychosis”
    • Also stated in: § Conclusions/future directions · plain
      “This review found that the risk of psychosis is significantly elevated with frequent, i.e., at least weekly, cannabis use”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Study design and conductreasoning

    Certainty-in-findings was rated as moderate according to GRADE, largely due to the observational nature of study designs and heterogeneity.

    “Certainty-in-findings was rated as moderate according (GRADE), largely due to the observational nature of study designs and heterogeneity”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    Recent reviews have confirmed a moderately significant association between cannabis use and psychosis.

    “Recent reviews have confirmed a moderately significant association between cannabis use and psychosis (Kiburi, Molebatsi, Ntlantsana, & Lynskey, 2021; Polkosnik, Sorkhou, & George, 2021; van der Steur, Batalla, & Bossong, 2020).”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Kiburi, Molebatsi, Ntlantsana, & Lynskey, 2021

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    • cites Polkosnik, Sorkhou, & George, 2021

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    • cites van der Steur, Batalla, & Bossong, 2020

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  • May combine two claims.

    Interpretationown data

    Individuals using cannabis frequently are at increased risk of psychosis, with no significant risk associated with less frequent use.

    “Individuals using cannabis frequently are at increased risk of psychosis, with no significant risk associated with less frequent use.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductown data

    Inter-rater reliability was 96% agreement (κ = 0.60) for title and abstract screening and 92% agreement (κ = 0.62) for full-text screening.

    “Inter-rater reliability was 96% agreement (κ = 0.60) for title and abstract screening and 92% agreement (κ = 0.62) for full-text screening, respectively, indicating substantial agreement.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Frequent cannabis use functions as a strong predictor of psychosis and other adverse outcomes.

    “Frequent cannabis use, specifically, has been shown to function as a strong predictor of psychosis and other adverse outcomes (e.g. cognitive functioning, psychosocial outcomes and CUD) (Fischer et al., 2022; Kroon, Kuhns, Hoch, & Cousijn, 2020; Leung et al., 2020; Lorenzetti, Chye, Silva, Solowij, & Roberts, 2019).”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Fischer et al., 2022

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    • cites Kroon, Kuhns, Hoch, & Cousijn, 2020

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    • cites Leung et al., 2020

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Current evidence suggests that the legalization of non-medical cannabis use may lead to an increased incidence of psychosis.

    “Current evidence however, suggests that the legalization of non-medical cannabis use may lead to an increased incidence of psychosis (Hamilton & Monaghan, 2019; Ksir & Hart, 2016; Murray & Hall, 2020).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Hamilton & Monaghan, 2019

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    • cites Ksir & Hart, 2016

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    • cites Murray & Hall, 2020 source

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  • Classified as probably not a substantial claim.

    Premisecitation

    Most frequent cannabis use is associated with a four-fold increase in odds of psychosis (OR 3.90, 95% CI 2.84-5.34) compared to non-use.

    “Another meta-analysis showed a four-fold increase in odds of psychosis (OR 3.90, 95%CI 2.84–5.34) for the most frequent cannabis use”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Marconi, Di Forti, Lewis, Murray, & Vassos, 2016

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductcitation

    Sensitivity analyses were performed using both quadratic and flexible non-linear models with restricted cubic splines with three knots.

    “Sensitivity analyses were performed using both quadratic and flexible non-linear models with restricted cubic splines with three knots (10th, 50th, and 90th percentiles) of the distribution”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Liu, Cook, Bergström, & Hsieh, 2009

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    • cites Orsini, Bellocco, & Greenland, 2006

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    The study protocol was registered pre-initiation with PROSPERO (#CRD42021234708).

    “The study protocol was registered pre-initiation with the International Register of Systematic Reviews (PROSPERO)(#CRD42021234708).”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Study design and conductcitation

    Goodness-of-fit statistics (AIC, deviance test D, and R2) were assessed to select the best-fitting model.

    “Goodness-of-fit statistics (Akaike information criteria ‘AIC’, deviance test ‘D’, and the coefficient of determination ‘R2’) were assessed to select the best-fitting model”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Discacciati, Crippa, & Orsini, 2017

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The role of cannabis use in the incidence of psychotic outcomes as a causal contributor is complex, because their causes are multifactorial, influenced by the environment, genes and their interactions.

    “The role of cannabis use in the incidence of psychotic outcomes as a causal contributor is complex, because their causes are known to be multifactorial, being influenced by the environment, genes and their interactions (Ben Amar & Potvin, 2007; Hall & Degenhardt, 2008; Hamilton, 2017; Wright et al., 2020).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Ben Amar & Potvin, 2007

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    • cites Hall & Degenhardt, 2008

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    • cites Hamilton, 2017

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductcitation

    The Newcastle Ottawa Scale was used to assess the risk of bias of included studies.

    “The RoB of included studies was assessed using the Newcastle Ottawa Scale versions for both cohort and case–control studies”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Wells et al., 2013

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    A two-fold increase in odds of psychosis (AOR = 2.09, 95% CI 1.54-2.84) was found in a comparison of frequent to no cannabis use.

    “Elsewhere, a two-fold increase (AOR = 2.09, 95% CI 1.54–2.84) in the odds of psychosis had been found in a comparison of frequent to no cannabis use (Moore et al., 2007).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Moore et al., 2007 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductnone given

    Study data were extracted by two independent reviewers, using consensus discussions for disagreements, and final data verifications conducted by the study statistician.

    “Study data were extracted by two independent reviewers, using consensus discussions for disagreements, and final data verifications conducted by the study statistician.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Beyond use frequency, epidemiological data have identified high potency cannabis, early age-of-use onset (e.g. pre-25), childhood trauma, and concurrent other substance use as contributing factors to psychosis development.

    “Beyond the role of use frequency, epidemiological data have identified the use of high potency cannabis, early age-of-use onset (e.g. pre-25), childhood trauma, and concurrent other substance use as contributing factors to psychosis development (Di Forti et al., 2015; Hall & Lynskey, 2020; Kiburi et al., 2021; van der Steur et al., 2020).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Di Forti et al., 2015 source

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    • cites Hall & Lynskey, 2020

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    • cites Kiburi et al., 2021

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  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductnone given

    Citations were screened initially by title and abstract in duplicate by two independent reviewers, with full-text screening completed in the same manner.

    “Citations were screened initially by title and abstract in duplicate by two independent reviewers, with full-text screening completed in the same manner.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductcitation

    Certainty-in-findings for the primary review outcome was assessed using GRADE.

    “Certainty-in-findings for the primary review outcome was assessed using the Grading of Recommendations Assessment, Development and Evaluations (GRADE) approach”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Schunemann, Brozek, Guyatt, & Oxam, 2013

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Systematic reviews have quantified exposure levels of alcohol use that represent risk-thresholds for stroke, cardio-vascular disease and atrial fibrillation.

    “For example, systematic reviews have quantified exposure levels of alcohol use (e.g. by standard drinks/week) that represent risk-thresholds for stroke, cardio-vascular disease and atrial fibrillation (Samokhvalov, Irving, & Rehm, 2010; Tu et al., 2021; Wood et al., 2018)”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Samokhvalov, Irving, & Rehm, 2010

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    • cites Tu et al., 2021

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    • cites Wood et al., 2018 source

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    Premisecitation

    Recent research has confirmed the importance of genetic influences, specifically polymorphisms on specific genes (e.g. COMT, AKT1) that make affected individuals more vulnerable to the psychogenetic effects of cannabis.

    “Recent research has confirmed the importance of genetic influences, specifically polymorphisms on specific genes (e.g. COMT, AKT1) that make affected individuals more vulnerable to the psychogenetic effects of cannabis (Misiak et al., 2018; Polkosnik et al., 2021; van der Steur et al., 2020).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Misiak et al., 2018

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    • cites Polkosnik et al., 2021

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    • cites van der Steur et al., 2020

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    Study design and conductcitation

    The systematic review and meta-analysis were conducted in accordance with PRISMA 2020.

    “This systematic review and meta-analysis were conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 framework”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Page et al., 2021

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  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductnone given

    Risk of bias assessments were completed in duplicate by two independent reviewers and disagreements resolved through consensus.

    “RoB assessments were completed in duplicate by two independent reviewers and disagreements resolved through consensus discussions.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S2 (checkable), S4 (based).

    Interpretationreasoning

    If risk-thresholds for cannabis use frequency and psychosis can be identified, these may inform prevention/educational messages toward reducing cannabis-related harm among users.

    “If risk-thresholds for cannabis use frequency and psychosis can be identified, these may inform prevention/educational messages toward reducing cannabis-related harm among users.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Study design and conductreasoning

    All included studies are observational designs, and therefore overall study quality is lower and potential risk of bias higher than if randomized trials were utilized.

    “While included studies were rated as having a low RoB according to the Newcastle Ottawa Scale, it is important to note that all included studies are observational designs and therefore overall study quality is lower and the potential RoB higher than if randomized trials were utilized.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    All studies assessed were included in this review, regardless of their methodological quality.

    “All studies assessed were included in this review, regardless of their methodological quality.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Study design and conductown data

    Most included studies did not report data on potential contributor factors for outcomes, so these factors could not be controlled for.

    “First, most of the included studies did not report data on potential contributor factors for outcomes, which therefore could not be controlled for.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    Existing prevention content commonly conveys categorical warnings regarding the link between cannabis use and risk for psychosis.

    “While existing prevention content commonly convey categorical warnings regarding the link between cannabis use and risk for psychosis”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Ghonaim, 2018

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    • cites Ladegard, Thurstone, & Rylander, 2020

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    • cites Murray, David, & Ajnakina, 2021

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    Study design and conductcitation

    Case-control studies with less than ten matched-pairs were excluded due to the increased risk of bias.

    “Case–control studies with less than ten matched-pairs were excluded due to the increased risk of bias (RoB) encountered in studies with sample sizes below this threshold”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Dekkers et al., 2019 source

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    Study design and conductcitation

    Publication bias was assessed by funnel plots, whereby regression/mixed-effects models and variance/standard errors assessed funnel plot asymmetry.

    “Publication bias was assessed by funnel plots, whereby regression/mixed-effects models and variance/standard errors assessed funnel plot asymmetry”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Sterne & Egger, 2005 source

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  • Classified as probably not a substantial claim.

    Interpretationreasoning

    The review's results translate into a refinement of prevention/education messages, such as those offered by the LRCUG or other pertinent recommendation sources.

    “These results translate into the consequential refinement of prevention/education messages, for example as offered by the LRCUG (Fischer et al., 2022) or other pertinent recommendation sources.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Fischer et al., 2022

      Not checked in the free run.

    • Rests on an assumption: The association between frequent cannabis use and psychosis is causal, such that reducing cannabis use frequency would meaningfully lower the risk of cannabis-attributable psychosis.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Exposure-stepped, evidence-based prevention messaging about risk-thresholds for cannabis use and psychosis is analogous to evidence-based alcohol-related health guidelines where risk for specific adverse outcomes is low or absent below certain consumption levels and moderate use is recommended.

    “However, it is analogous to evidence-based alcohol-related health guidelines where the risk for specific adverse (e.g. cardio-vascular) outcomes is low/absent below certain consumption levels and ‘moderate’ use is recommended”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Furtwaengler & de Visser, 2013

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    • cites Holmes et al., 2019

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    • cites Wood et al., 2018 source

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  • May combine two claims.

    Study design and conductnone given

    All included studies utilized self-report measures of cannabis use frequency, which may be prone to recall bias.

    “All included studies utilized self-report measures of cannabis use frequency, which may be prone to recall bias.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The use of high-potency cannabis increases the risk of a psychotic disorder.

    “the use of high-potency cannabis also increases the risk of a psychotic disorder (van der Steur et al., 2020)”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites van der Steur et al., 2020

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    The identification of risk-thresholds was limited to the a-priori defined frequency categories.

    “The identification of risk-thresholds was limited to the a-priori defined frequency categories.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductcitation

    Statistical heterogeneity was assessed using the I2 statistic.

    “Statistical heterogeneity was assessed using the I2 statistic, with thresholds assessed according to standard recommendations”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Deeks, Higgins, & Altman, 2019 source

      Not checked in the free run.

38 of 38

  • The paper relies on this without support.

    The association between frequent cannabis use and psychosis is causal, such that reducing cannabis use frequency would meaningfully lower the risk of cannabis-attributable psychosis.

    “Cannabis users, however, should be explicitly advised by evidence-based prevention messaging to keep their cannabis use infrequent in order for their risks for cannabis-attributable psychosis development to be meaningfully lowered.”
1 of 1

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Yearly-use risk ratio conflicts with Table 2

    Minor

    The results text reports RR 1.25 for yearly use, but Table 2 reports 1.15. The stated confidence interval of 1.10-1.20 also excludes 1.25.

  • Discussion attaches a percent sign to the daily-use risk ratio

    Minor

    The discussion writes the risk ratio as 1.76%, while the abstract reports it as the dimensionless value 1.76.

  • Daily-use linear-model risk ratio differs from Table 2

    Minor

    The results text reports RR 1.71 for daily/near-daily use, whereas Table 2 reports 1.73 for the same model and category.

  • Quadratic-model daily-use confidence interval differs from Table 2

    Minor

    The sensitivity-analysis text gives a lower confidence limit of 1.29 for daily/near-daily use; Table 2 gives 1.49.

4 of 4

Cites

Flagged first, then by citations

Research works printed but not linked: 9

  1. Ghonaim, H. (2018). Health expert warns of lack of awareness about effects of pot [Press release]. Retrieved from https://www.cbc.ca/news/canada/london/canadians-unaware-of-cannabis-risk-factors-1.4615380.
  2. 2013, Diagnostic and statistical manual of mental disorders
  3. 2019, Stata stasticial software: Release 16
  4. 2020, R: A language and environment for statistical computing
  5. 2017, The health effetcs of Cannabis and cannabinoids: The current state of evidence and recommendations for research
  6. 2018, International classification of diseases for mortality and morbidity statistics (11th revision)
  7. 2021, Covidence
  8. Schunemann, 2013, Handbook for grading the quality of evidence and the strength of recommendations using the GRADE approach
  9. Young, 2021, Developing lower-risk gambling guidelines

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Related

Authors
Robinson, T., Ali, M. U., Easterbrook, B., Hall, W., Jutras-Aswad, D., & Fischer, B.
Affiliations
  • Simon Fraser University (CA)
  • McMaster University (CA)
  • The University of Queensland (AU)
  • University of Auckland (NZ)
Corresponding author
Fischer, Benedikt
ORCID
Venue
Psychological Medicine
Publisher
Cambridge University Press (CUP)
Published
2022-03-24
Volume
53
Issue
9
Pages
3858-3868
ISSN
  • 0033-2917 (ISSN-L)
  • 1469-8978
DOI
10.1017/s0033291722000502
PMC
PMC10317818
OpenAlex
W4220795102
Semantic Scholar
99680a9ac4522f0befaa4d95069c6efd488e4309
Cited by
68
References
78
Citations by year
2026: 20 · 2025: 10 · 2024: 16 · 2023: 15 · 2022: 7
FWCI
1.72
Type
journal article
Language
en
Open access
Licence
Locations
  • Psychological Medicine (publishedVersion, cc-by-nc-nd)
  • PubMed Central (publishedVersion, cc-by-nc-nd)
  • PubMed (publishedVersion)
Funders
Health Canada
Topics
  • Health Sciences › Medicine › Pharmacology › Cannabis and Cannabinoid Research
  • Health Sciences › Medicine › Psychiatry and Mental health › Schizophrenia research and treatment
  • Life Sciences › Pharmacology, Toxicology and Pharmaceutics › Toxicology › Forensic Toxicology and Drug Analysis
Keywords
cannabis use, psychosis, psychosis risk, dose-response relationship, cannabis use frequency, risk thresholds, daily cannabis use, cannabis-related psychosis
MeSH terms
Adolescent, Adult, Aged, Cannabis, Child, Humans, Middle Aged, Psychotic Disorders, Cohort Studies, Case-Control Studies, Young Adult

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-09.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-09.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

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