Genetic evidence suggests cannabis use disorder may lower educational attainment, while education reduces disorder risk | Research

The takeaway

Using genetic variants as proxies, researchers found a bidirectional relationship: genetic liability to cannabis use disorder was associated with 1.2 fewer months of education, while higher educational attainment was associated with lower CUD risk but higher lifetime cannabis use.

Genetic epidemiologists, addiction researchers, education policy researchers

Higher education: 35% more likely to try cannabis, 61% less likely to develop disorder

What the researchers found

Bidirectional Mendelian randomization found genetic liability to cannabis use disorder was associated with 1.2 fewer months of education (P=0.0008). Lifetime cannabis use showed no significant effect on education. In the reverse direction, higher educational attainment was associated with 61% lower CUD risk (OR 0.39, P=1.69x10^-10) but 35% higher lifetime cannabis use (OR 1.35, P=0.003). The CUD-education relationship may be partially explained by shared ADHD risk factors.

Why it matters

This study uses genetic instruments to approximate causal inference, suggesting the relationship between cannabis and education is more nuanced than observational studies indicate. Problematic use may impair education, while education may increase experimental use but protect against problematic use.

The numbers in context

Sample sizes 55,374-632,802; CUD reduced education by 1.2 months (P=0.0008); lifetime cannabis use: no effect on education (P=0.60); education reduced CUD: OR 0.39 (P=1.69x10^-10); education increased lifetime use: OR 1.35 (P=0.003)

How the study worked

Bidirectional two-sample Mendelian randomization using genome-wide association study summary statistics from European ancestry samples (55,374 to 632,802 participants). Primary method was inverse-variance weighted MR with sensitivity analyses. Multivariable MR adjusted for intelligence, smoking initiation, and ADHD.

What this study cannot tell us

Limited to European ancestry populations. Mendelian randomization assumptions (no pleiotropy, no direct instrument effects) may not fully hold. Shared ADHD risk factors complicate interpretation. Cannot specify mechanisms by which CUD affects education.

How to read the evidence

Large-scale Mendelian randomization with multiple sensitivity analyses and multivariable adjustment, though limited to European ancestry.

When this study was published

Published 2023

The bigger picture

The finding that education increases lifetime cannabis use but decreases cannabis use disorder challenges the assumption that any cannabis use leads to problematic outcomes. The distinction between use and disorder matters.

Questions still open

What specific aspects of CUD drive educational impairment? Does the education-cannabis relationship vary across non-European populations?

Common questions

Does cannabis use reduce educational attainment?

This genetic analysis found that cannabis use disorder (not just any use) was associated with 1.2 fewer months of education. Lifetime cannabis use alone showed no significant effect on education.

Does education affect cannabis use?

Interestingly, higher educational attainment was associated with 35% higher odds of ever using cannabis but 61% lower odds of developing cannabis use disorder, suggesting education may increase experimentation while protecting against problematic use.

Read the original research

Genetic support of a causal relationship between cannabis use and educational attainment: a two-sample Mendelian randomization study of European ancestry.

Addiction (Abingdon, England), 118(4), 698-710

View on PubMed ↗Publisher’s paper ↗

Citation

Chen, Dongze; Wang, Xinpei; Huang, Tao; Jia, Jinzhu. (2023). Genetic support of a causal relationship between cannabis use and educational attainment: a two-sample Mendelian randomization study of European ancestry.. Addiction (Abingdon, England), 118(4), 698-710. https://doi.org/10.1111/add.16090