Effects of education mediated by brain size on regional brain volume in adults

•What is the primary question addressed by this study?We aimed to investigate the mediating effect of ICV on the association between educational attainment in early life and regional brain volume in later life.•What is the main finding of this study?Our results showed that the effect of education on regional brain volume was significantly mediated by ICV in both men and women. The indirect (mediated via ICV) effect of education on brain volume amounted to 75% of the total effect in the hippocampus (p < 0.001) and 100% in the frontal and insular gray matter (p < 0.001).•What is the meaning of the finding?Our study demonstrated that the association between educational attainment in early life and regional brain volume in later life was largely mediated by ICV. Attention should be given to the effect of educational attainment and ICV on regional brain size in adults as a measurable resilience effect in brain aging.