Combat stress in a small-scale society suggests divergent evolutionary roots for posttraumatic stress disorder symptoms

Matthew R. Zefferman, Sarah Mathew

Research output: Contribution to journalArticlepeer-review

Abstract

Military personnel in industrialized societies often develop posttraumatic stress disorder (PTSD) during combat. It is unclear whether combat-related PTSD is a universal evolutionary response to danger or a culture-specific syndrome of industrialized societies. We interviewed 218 Turkana pastoralist warriors in Kenya, who engage in lethal cattle raids, about their combat experiences and PTSD symptoms. Turkana in our sample had a high prevalence of PTSD symptoms, but Turkana with high symptom severity had lower prevalence of depression-like symptoms than American service members with high symptom severity. Symptoms that facilitate responding to danger were better predicted by combat exposure, whereas depressive symptoms were better predicted by exposure to combat-related moral violations. The findings suggest that some PTSD symptoms stem from an evolved response to danger, while depressive PTSD symptoms may be caused by culturally specific moral norm violations.

Original languageEnglish (US)
Article numbere2020430118
JournalProceedings of the National Academy of Sciences of the United States of America
Volume118
Issue number15
DOIs
StatePublished - Apr 13 2021

Keywords

  • Combat stress
  • Cross-cultural psychology
  • Evolutionary medicine
  • Moral injury
  • PTSD

ASJC Scopus subject areas

  • General

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