Cannabis Use During Adolescence and Young Adulthood and Academic Achievement: A Systematic Review and Meta-Analysis.

Importance: Cannabis use during adolescence and young adulthood may affect academic achievement; however, the magnitude of association remains unclear.

Objective: To conduct a systematic review evaluating the association between cannabis use and academic performance.

Data sources: CINAHL, EMBASE, MEDLINE, PsycInfo, PubMed, Scopus, and Web of Science from inception to November 10, 2023.

Study selection: Observational studies examining the association of cannabis use with academic outcomes were selected. The literature search identified 17 622 unique citations.

Data extraction and synthesis: Pairs of reviewers independently assessed risk of bias and extracted data. Both random-effects models and fixed-effects models were used for meta-analyses, and the Grading of Recommendations Assessment, Development, and Evaluation approach was applied to evaluate the certainty of evidence for each outcome. Data were analyzed from April 6 to May 25, 2024.

Main outcomes and measures: School grades, school dropout, school absenteeism, grade retention, high school completion, university enrollment, postsecondary degree attainment, and unemployment.

Results: Sixty-three studies including 438 329 individuals proved eligible for analysis. Moderate-certainty evidence showed cannabis use during adolescence and young adulthood was probably associated with lower school grades (odds ratio [OR], 0.61 [95% CI, 0.52-0.71] for grade B and above); less likelihood of high school completion (OR, 0.50 [95% CI, 0.33-0.76]), university enrollment (OR, 0.72 [95% CI, 0.60-0.87]), and postsecondary degree attainment (OR, 0.69 [95% CI, 0.62-0.77]); and increased school dropout rate (OR, 2.19 [95% CI, 1.73-2.78]) and school absenteeism (OR, 2.31 [95% CI, 1.76-3.03]). Absolute risk effects ranged from 7% to 14%. Low-certainty evidence suggested that cannabis use may be associated with increased unemployment (OR, 1.50 [95% CI, 1.15-1.96]), with an absolute risk increase of 9%. Subgroup analyses with moderate credibility showed worse academic outcomes for frequent cannabis users and for students who began cannabis use earlier.

Conclusions and relevance: Cannabis use during adolescence and young adulthood was probably associated with increases in school absenteeism and dropout; reduced likelihood of obtaining high academic grades, graduating high school, enrolling in university, and postsecondary degree attainment; and perhaps increased unemployment. Further research is needed to identify interventions and policies that mitigate upstream and downstream factors associated with early cannabis exposure.