Associations between adolescent cannabis use and young-adult functioning in three longitudinal twin studies

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5 Scopus citations


Observational studies have linked cannabis use to an array of negative outcomes, including psychiatric symptoms, cognitive impairment, and educational and occupational underachievement. These associations are particularly strong when cannabis use occurs in adolescence. Nevertheless, causality remains unclear. The purpose of the present study was thus to examine associations between prospectively assessed adolescent cannabis use and young-adult outcomes (psychiatric, cognitive, and socioeconomic) in three longitudinal studies of twins (n = 3,762). Twins reporting greater cumulative cannabis use in adolescence reported higher levels of psychopathology as well as poorer socioeconomic outcomes in young adulthood. However, cannabis use remained associated only with socioeconomic outcomes (i.e., educational attainment, occupational status, and income) in monozygotic-cotwin control analyses, which account fully for shared genetic and environmental confounding. Follow-up analyses examining associations between twin differences in adolescent cannabis use and longitudinal change in academic functioning during the middle- and high-school years provided a possible mechanism for these associations, indicating that greater cannabis use during this period was associated with decreases in grade point average and academic motivation as well as increases in academic problem behavior and school disciplinary problems. Our findings thus suggest that cannabis use in adolescence has potentially causal, deleterious effects on adolescent academic functioning and youngadult socioeconomic outcomes despite little evidence suggesting a strong, causal influence on adult mental health or cognitive ability.

Original languageEnglish (US)
Article numbere2013180118
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number14
StatePublished - Apr 6 2021

Bibliographical note

Funding Information:
ACKNOWLEDGMENTS. Research reported in this article was supported by the National Institute of Mental Health, the National Institute on Drug Abuse, and the National Institute on Alcohol Abuse and Alcoholism of the NIH under Award No. T32MH015755 (J.D.S.), R01DA037904 (S.V.), R01DA044283 (S.V.), R37DA005147 (W.G.I), R01DA036216 (W.G.I.), R01DA042755 (S.V. and M.M.), R21AA026919 (S.M.M.), R21AA026632 (S.W.), and K01DA037280 (S.W.). The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.

Publisher Copyright:
© 2021 National Academy of Sciences. All rights reserved.


  • Adolescence
  • Cannabis
  • Education
  • Marijuana
  • Twin

PubMed: MeSH publication types

  • Journal Article
  • Research Support, N.I.H., Extramural
  • Twin Study


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