Beyond years of schooling: Genetic associations across educational milestones in two Norwegian cohorts
- 1Center for Lifespan Changes in Brain and Cognition, Department of Psychology, University of Oslo, Oslo, Norway
- 2Department of Sociology and Human Geography, University of Oslo, Oslo, Norway
- 3Ragnar Frisch Centre for Economic Research, Oslo, Norway
Abstract
Although educational attainment is heritable, years-of-education (EduYears) measures are not designed to show how genetic associations vary across discrete educational milestones. In the Norwegian Mother, Father and Child Cohort Study (MoBa; N = 120,527) and the Norwegian Twin Registry (N = 8,910), we combined genome-wide association studies (GWAS), polygenic indices (PGIs), and twin models to characterize genetic associations with high-school completion and bachelor’s, master’s, and doctoral attainment. In transition-specific analyses conditional on prior attainment, observed-scale common-variant heritability (h2SNP) and PGI discrimination followed an inverse-U pattern, peaking for progression from high-school completion to attainment of at least a bachelor’s degree (HS → BSc + ; h2SNP ≈ 0.14; R2Tjur ≈ 0.05) and declining at postgraduate transitions. Genetic correlations (rg) with large-scale GWAS of EduYears (EA4) and intelligence were high at earlier transitions but lower at later ones (for EA4, rg ≈ 0.92 at HS → BSc+ and ≈ 0.38 at MSc → PhD). In cumulative analyses of attained status in the full cohort, the point-estimate gap between twin- and SNP-based heritability narrowed from ≈ 0.38 at high-school completion to ≈ 0.11 at PhD, while genetic overlap was lower for distant than adjacent milestones (rg ≈ 0.71 for high-school completion versus PhD and ≈ 0.92 for adjacent milestones). Sensitivity analyses using an alternative intelligence GWAS and additional PGIs showed similar transition-specific trajectories. At the doctoral transition, estimates were obtained among individuals who had attained at least a master’s degree, so attenuation there must be interpreted in light of selection and range restriction. Because EduYears converts distinct credentials and progression steps into a single numerical scale, estimates expressed per additional year should not be interpreted as though one year has the same meaning across the educational sequence. Milestone-preserving analyses make that hidden structure visible and sharpen the interpretation of education GWAS and PGIs. Author summary: Genetic studies of education usually summarize attainment as years of schooling. Yet people do not simply accumulate years; they progress through credentials such as high school, bachelor’s, master’s, and doctoral degrees. We analyzed these milestones in two Norwegian cohorts containing more than 120,000 genotyped adults and nearly 9,000 twins. Among high-school graduates, analyses based on common DNA variants and genetic scores showed the clearest signal when comparing those who attained at least a bachelor’s degree with those whose highest credential was high school. Signals were weaker at the ends of the sequence, but those comparisons also had different structures: high-school completion is nearly universal in Norway, while doctoral progression is assessed among people who have already passed several earlier milestones. Twin analyses produced their highest heritability estimate for high-school completion, although uncertainty was substantial. These findings show that genetic results depend on the educational contrast being studied and on who is included in the comparison group. A single years-based measure compresses these differences, and one additional year should not be assumed to represent the same educational step throughout the sequence. Treating education as milestones provides a clearer basis for interpreting genetic studies of education.
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BibTeX
@article{kvalvik2026beyond,
title = {{Beyond years of schooling: Genetic associations across educational milestones in two Norwegian cohorts}},
author = {Eirik Haugland Kvalvik and Yunpeng Wang and Kristine Beate Walhovd and Torkild Hovde Lyngstad and Ole Røgeberg},
journal = {PLOS Genetics},
year = {2026},
month = sep,
doi = {10.1371/journal.pgen.1012310},
url = {https://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1012310},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Beyond years of schooling: Genetic associations across educational milestones in two Norwegian cohorts
AU - Eirik Haugland Kvalvik
AU - Yunpeng Wang
AU - Kristine Beate Walhovd
AU - Torkild Hovde Lyngstad
AU - Ole Røgeberg
PY - 2026
DA - 2026/09/17
JO - PLOS Genetics
DO - 10.1371/journal.pgen.1012310
UR - https://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1012310
AB - Although educational attainment is heritable, years-of-education (EduYears) measures are not designed to show how genetic associations vary across discrete educational milestones. In the Norwegian Mother, Father and Child Cohort Study (MoBa; N = 120,527) and the Norwegian Twin Registry (N = 8,910), we combined genome-wide association studies (GWAS), polygenic indices (PGIs), and twin models to characterize genetic associations with high-school completion and bachelor’s, master’s, and doctoral attainment. In transition-specific analyses conditional on prior attainment, observed-scale common-variant heritability (h2SNP) and PGI discrimination followed an inverse-U pattern, peaking for progression from high-school completion to attainment of at least a bachelor’s degree (HS → BSc + ; h2SNP ≈ 0.14; R2Tjur ≈ 0.05) and declining at postgraduate transitions. Genetic correlations (rg) with large-scale GWAS of EduYears (EA4) and intelligence were high at earlier transitions but lower at later ones (for EA4, rg ≈ 0.92 at HS → BSc+ and ≈ 0.38 at MSc → PhD). In cumulative analyses of attained status in the full cohort, the point-estimate gap between twin- and SNP-based heritability narrowed from ≈ 0.38 at high-school completion to ≈ 0.11 at PhD, while genetic overlap was lower for distant than adjacent milestones (rg ≈ 0.71 for high-school completion versus PhD and ≈ 0.92 for adjacent milestones). Sensitivity analyses using an alternative intelligence GWAS and additional PGIs showed similar transition-specific trajectories. At the doctoral transition, estimates were obtained among individuals who had attained at least a master’s degree, so attenuation there must be interpreted in light of selection and range restriction. Because EduYears converts distinct credentials and progression steps into a single numerical scale, estimates expressed per additional year should not be interpreted as though one year has the same meaning across the educational sequence. Milestone-preserving analyses make that hidden structure visible and sharpen the interpretation of education GWAS and PGIs. Author summary: Genetic studies of education usually summarize attainment as years of schooling. Yet people do not simply accumulate years; they progress through credentials such as high school, bachelor’s, master’s, and doctoral degrees. We analyzed these milestones in two Norwegian cohorts containing more than 120,000 genotyped adults and nearly 9,000 twins. Among high-school graduates, analyses based on common DNA variants and genetic scores showed the clearest signal when comparing those who attained at least a bachelor’s degree with those whose highest credential was high school. Signals were weaker at the ends of the sequence, but those comparisons also had different structures: high-school completion is nearly universal in Norway, while doctoral progression is assessed among people who have already passed several earlier milestones. Twin analyses produced their highest heritability estimate for high-school completion, although uncertainty was substantial. These findings show that genetic results depend on the educational contrast being studied and on who is included in the comparison group. A single years-based measure compresses these differences, and one additional year should not be assumed to represent the same educational step throughout the sequence. Treating education as milestones provides a clearer basis for interpreting genetic studies of education.
SN - 1553-7404
ER -