A new study suggests that combat-related PTSD symptomology is found in non-Western, small-scale societies, even where combat is celebrated and social support for warriors is high. However, the findings also suggest that depressive PTSD symptoms are more common among American veterans, possibly due to the violation of culturally specific moral norms against engaging in combat. The findings were published in the Proceedings of the National Academy of Sciences.
In industrialized societies, members of the armed forces commonly develop symptoms of posttraumatic stress disorder (PTSD) — a condition characterized by intense fear, anxiety, and flashbacks surrounding a traumatic event. Throughout the psychology literature, scholars have debated whether PTSD is a universal disorder with evolutionary origins or whether the condition is unique to Western societies.
Notably, it has been suggested that combat-related PTSD symptoms might present differently across cultures, perhaps depending on a population’s social norms. To explore this, study authors Matthew R. Zefferman and Sarah Mathew set out to compare the prevalence of PTSD symptoms among a large-scale industrialized society with the prevalence of symptoms among a nonindustrialized population. Specifically, the researchers compared PTSD symptoms among American veterans and Turkana warriors from a small-scale society in Kenya.
“The Turkana communities in this area see cattle raiding as integral to their livelihood – without going on raids, they cannot recover livestock they lost when they were attacked, and they would get pushed out of critical dry season pastures and water wells,” said Mathew.
Both American service members and Turkana warriors responded to 20 items assessing how often they had experienced a range of PTSD symptoms within the last month. Only respondents who met the cutoff for clinical PTSD were maintained for analysis.
First, the analysis offered evidence that combat-related PTSD is not unique to industrialized societies. Among those who were interviewed, 28% of Turkana warriors had PTSD scores above 33, which is considered the clinical cutoff for PTSD among Western samples. However, the pattern of symptoms they showed was somewhat different compared to the American veterans.
Both groups were about as likely to show PTSD symptoms that the researchers referred to as “learning” symptoms — symptoms that may have evolved because they help trauma survivors learn about acute dangers (e.g., nightmares, flashbacks, and cued physical reactions). Both groups were also equally likely to show “reacting” symptoms — symptoms that may have evolved because they teach people to react quickly to danger (e.g., hypervigilance). These findings suggest that at least some aspects of PTSD have an evolutionary basis and are shared across cultures.
However, the Turkana warriors were less likely than the American veterans to present with the five depressive symptoms of detachment, loss of interest, low concentration, irritability, and negative feelings. According to Zefferman and Mathew, this suggests that depression-like PTSD symptoms are culturally influenced.
“The findings provide an evolutionarily and cross-culturally informed framework to further probe the origins and causes of moral injury and its connection to combat-related PTSD,” said Zefferman.
The authors point out that Turkana cultural norms and beliefs likely play a role in the reduced severity of depressive symptoms when compared to American service members. Among the Turkana people, participation in combat is widely supported, killing during combat is typically celebrated, and raiders likely do not expect to encounter moral disapproval. Moreover, combat is a commonly shared experience.
Among Americans, however, participation in combat is a much more isolated experience. “Most Americans cannot relate to the experiences of those who have participated in combat,” Zefferman and Mathew write in their study. “Consequently, warfare presents a moral conflict because what is considered a soldier’s duty in combat can violate prevailing moral norms within the soldier’s society. American soldiers may therefore have a heightened awareness of potential social repercussions especially as they integrate back into civilian life.”
Support groups for veterans offer service members community support and a chance to share their experiences, but these services are likely not comparable to the social support in place for Turkana warriors. The authors note that their findings are preliminary and will need to be strengthened with additional longitudinal studies.
The study, “Combat stress in a small-scale society suggests divergent evolutionary roots for posttraumatic stress disorder symptoms”, was authored by Matthew R. Zefferman and Sarah Mathew.