Collective Optimism and Selection Against Male Twins in Utero

Ralph A. Catalano, Sidra Goldman-Mellor, Deborah A. Karasek, Alison Gemmill, Joan A. Casey, Holly Elser, Tim A. Bruckner, Terry Hartig

Research output: Contribution to journalArticlepeer-review


Scholarly literature claims that health declines in populations when optimism about investing in the future wanes. This claim leads us to describe collective optimism as a predictor of selection in utero. Based on the literature, we argue that the incidence of suicide gauges collective optimism in a population and therefore willingness to invest in the future. Using monthly data from Sweden for the years 1973-2016, we test the hypothesis that the incidence of suicide among women of child-bearing age correlates inversely with male twin births, an indicator of biological investment in high-risk gestations. We find that, as predicted by our theory, the incidence of suicide at month t varies inversely with the ratio of twin to singleton male births at month t + 3. Our results illustrate the likely sensitivity of selection in utero to change in the social environment and so the potential for viewing collective optimism as a component of public health infrastructure.

Original languageEnglish (US)
Pages (from-to)45-50
Number of pages6
JournalTwin Research and Human Genetics
Issue number1
StatePublished - Feb 1 2020


  • Suicide
  • collective optimism
  • twins

ASJC Scopus subject areas

  • Pediatrics, Perinatology, and Child Health
  • Obstetrics and Gynecology
  • Genetics(clinical)


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