Intelligence quotient decline following frequent or dependent cannabis use in youth: a systematic review and meta-analysis of longitudinal studies

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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 I ² = 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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Mental health of young people: a global public-health challenge.

Vikram Patel, Alan J Flisher, Sarah Hetrick … (2007)

Mental disorders account for a large proportion of the disease burden in young people in all societies. Most mental disorders begin during youth (12-24 years of age), although they are often first detected later in life. Poor mental health is strongly related to other health and development concerns in young people, notably lower educational achievements, substance abuse, violence, and poor reproductive and sexual health. The effectiveness of some interventions for some mental disorders in this age-group have been established, although more research is urgently needed to improve the range of affordable and feasible interventions, since most mental-health needs in young people are unmet, even in high-income countries. Key challenges to addressing mental-health needs include the shortage of mental-health professionals, the fairly low capacity and motivation of non-specialist health workers to provide quality mental-health services to young people, and the stigma associated with mental disorder. We propose a population-based, youth focused model, explicitly integrating mental health with other youth health and welfare expertise. Addressing young people's mental-health needs is crucial if they are to fulfil their potential and contribute fully to the development of their communities.

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Life-span changes of the human brain white matter: diffusion tensor imaging (DTI) and volumetry.

Lars T Westlye, Kristine B Walhovd, Anders M Dale … (2010)

Magnetic resonance imaging volumetry studies report inverted U-patterns with increasing white-matter (WM) volume into middle age suggesting protracted WM maturation compared with the cortical gray matter. Diffusion tensor imaging (DTI) is sensitive to degree and direction of water permeability in biological tissues, providing in vivo indices of WM microstructure. The aim of this cross-sectional study was to delineate age trajectories of WM volume and DTI indices in 430 healthy subjects ranging 8-85 years of age. We used automated regional brain volume segmentation and tract-based statistics of fractional anisotropy, mean, and radial diffusivity as markers of WM integrity. Nonparametric regressions were used to fit the age trajectories and to estimate the timing of maximum development and deterioration in aging. Although the volumetric data supported protracted growth into the sixth decade, DTI indices plateaued early in the fourth decade across all tested regions and then declined slowly into late adulthood followed by an accelerating decrease in senescence. Tractwise and voxel-based analyses yielded regional differences in development and aging but did not provide ample evidence in support of a simple last-in-first-out hypothesis of life-span changes.

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Association of Cannabis Use in Adolescence and Risk of Depression, Anxiety, and Suicidality in Young Adulthood

Gabriella Gobbi, Tobias Atkin, Tomasz Zytynski … (2019)

Cannabis is the most commonly used drug of abuse by adolescents in the world. While the impact of adolescent cannabis use on the development of psychosis has been investigated in depth, little is known about the impact of cannabis use on mood and suicidality in young adulthood.

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Author and article information

Journal

Journal ID (nlm-ta): Psychol Med

Journal ID (iso-abbrev): Psychol Med

Journal ID (publisher-id): PSM

Title: Psychological Medicine

Publisher: Cambridge University Press (Cambridge, UK )

ISSN (Print): 0033-2917

ISSN (Electronic): 1469-8978

Publication date (Print, pub): January 2021

Publication date (Electronic, pub): 27 January 2021

Volume: 51

Issue: 2

Pages: 194-200

Affiliations

[1 ]Department of Psychiatry, Royal College of Surgeons in Ireland, Education and Research Centre, Beaumont Hospital , Dublin 9, Ireland

[2 ]Trinity College Institute of Neuroscience, Trinity College Dublin , Dublin 2, Ireland

Author notes

Author for correspondence: Emmet Power, E-mail: emmetpower@ 123456rcsi.com

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Emmet Power https://orcid.org/0000-0001-9599-5474

Article

Publisher Item ID: S0033291720005036

DOI: 10.1017/S0033291720005036

PMC ID: 7893511

PubMed ID: 33501901

SO-VID: 9a1e4f25-d6f7-4a3a-b17a-d03cd49ba004

License:

This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence ( http://creativecommons.org/licenses/by/4.0), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited.

History

Date received : 12 May 2020

Date revision received : 22 October 2020

Date accepted : 02 December 2020

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Tables: 1, References: 48, Pages: 7

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Intelligence quotient decline following frequent or dependent cannabis use in youth: a systematic review and meta-analysis of longitudinal studies

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New Psychiatry

Most cited references 50

Mental health of young people: a global public-health challenge.

Life-span changes of the human brain white matter: diffusion tensor imaging (DTI) and volumetry.

Association of Cannabis Use in Adolescence and Risk of Depression, Anxiety, and Suicidality in Young Adulthood

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