Silventoinen, K, Bogl, LH, Jelenkovic, A, Vuoksimaa, E, Latvala, A, Li, W, Tan, Q, Zhang, D, Pang, Z, Ordoñana, JR, Sánchez-Romera, JF, Colodro-Conde, L, Willemsen, G, Bartels, M, van Beijsterveldt, CEM, Rebato, E, Corley, RP, Huibregtse, BM, Hopper, JL, Tyler, J, Duncan, GE, Buchwald, D, Silberg, JL, Maes, HH, Kandler, C, Cozen, W, Hwang, AE, Mack, TM, Nelson, TL, Whitfield, KE, Medda, E, Nisticò, L, Toccaceli, V, Krueger, RF, McGue, M, Pahlen, S, Martin, NG, Medland, SE, Montgomery, GW, Heikkilä, K, Derom, CA, Vlietinck, RF, Loos, RJF, Magnusson, PKE, Pedersen, NL, Dahl Aslan, AK, Hotopf, M, Sumathipala, A, Rijsdijk, F, Siribaddana, SH, Rose, RJ, Sørensen, TIA, Boomsma, DI and Kaprio, J (2021) Educational attainment of same-sex and opposite-sex dizygotic twins: An individual-level pooled study of 19 twin cohorts. Hormones and Behavior, 136. -. ISSN 0018-506X

[thumbnail of 1-s2.0-S0018506X21001331-main.pdf]
1-s2.0-S0018506X21001331-main.pdf - Published Version

Download (1MB) | Preview


Comparing twins from same- and opposite-sex pairs can provide information on potential sex differences in a variety of outcomes, including socioeconomic-related outcomes such as educational attainment. It has been suggested that this design can be applied to examine the putative role of intrauterine exposure to testosterone for educational attainment, but the evidence is still disputed. Thus, we established an international database of twin data from 11 countries with 88,290 individual dizygotic twins born over 100 years and tested for differences between twins from same- and opposite-sex dizygotic pairs in educational attainment. Effect sizes with 95% confidence intervals (CI) were estimated by linear regression models after adjusting for birth year and twin study cohort. In contrast to the hypothesis, no difference was found in women (β = -0.05 educational years, 95% CI -0.11, 0.02). However, men with a same-sex co-twin were slightly more educated than men having an opposite-sex co-twin (β = 0.14 educational years, 95% CI 0.07, 0.21). No consistent differences in effect sizes were found between individual twin study cohorts representing Europe, the USA, and Australia or over the cohorts born during the 20th century, during which period the sex differences in education reversed favoring women in the latest birth cohorts. Further, no interaction was found with maternal or paternal education. Our results contradict the hypothesis that there would be differences in the intrauterine testosterone levels between same-sex and opposite-sex female twins affecting education. Our findings in men may point to social dynamics within same-sex twin pairs that may benefit men in their educational careers.

Item Type: Article
Additional Information: © 2021 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license (
Subjects: R Medicine > RA Public aspects of medicine
R Medicine > RA Public aspects of medicine > RA0421 Public health. Hygiene. Preventive Medicine
Divisions: Faculty of Medicine and Health Sciences > School of Primary, Community and Social Care
Related URLs:
Depositing User: Symplectic
Date Deposited: 10 Nov 2021 10:31
Last Modified: 10 Nov 2021 10:31

Actions (login required)

View Item
View Item