The Nature of the Shared Environment

Research output: Contribution to journalArticle


While a standard part of twin modeling, the magnitude of shared environment (c2) is rarely examined by comparing estimates obtained using other methods. To clarify these effects on familial resemblance, we estimated c2 for 20 diverse phenotypes in: (i) monozygotic and dizygotic twins, (ii) all step-siblings, and (iii) reared together and apart half-siblings, ascertained from the Swedish general population. The mean c2 estimates (± 95% CIs) differed across methods and were higher from twins (0.18; 0.13–0.23) than from the step (0.12; 0.09–0.14) and half-sibs (0.09; 0.06–0.13). c2 estimates correlated moderately across these three methods (ICC = + 0.28). When step-siblings from blended (each sib biologically related to one parent) and adoption-like families (one sib offspring of both parents and one of neither), were examined separately, resemblance was much lower in the latter. We need to clarify the range of environmental processes now considered together under the term “shared environment.”


External organisations
  • Virginia Commonwealth University
  • Karolinska Institutet
  • Icahn School of Medicine at Mount Sinai
  • Shimane University
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Public Health, Global Health, Social Medicine and Epidemiology


  • Half-siblings, Shared environment, Step-siblings, Sweden, Twins
Original languageEnglish
Pages (from-to)1-10
JournalBehavior Genetics
Issue number1
Early online date2018 Dec
Publication statusPublished - 2019 Jan
Publication categoryResearch