Little evidence for association between posttraumatic combat stress and dysregulated cortisol and testosterone diurnal rhythm in Turkana pastoralists

A growing body of research suggests that post-traumatic stress disorder (PTSD) may be associated with decreased cortisol or testosterone sensitivity, resulting in a blunted diurnal rhythm. However, studies to date have primarily been conducted in Western industrialized populations, so it is unclear whether this PTSD-related hormonal blunting is a cross-cultural physiological response. Furthermore, these studies combine PTSD from diverse types of traumas, and the comparison groups with and without PTSD differ along multiple dimensions, making it hard to know if PTSD or other life factors drive the blunted cortisol response. Here, we conducted a study among n = 60 male Turkana pastoralists, aged between about 18-65 years in Kenya, exposed to high levels of lethal inter-ethnic cattle raiding. 28% of men in this area have PTSD symptom severity that would qualify them for a provisional PTSD diagnosis. Saliva samples were collected at three points (Waking, 8 AM, and 11 AM) to compare the cortisol and testosterone profiles of Turkana warriors with and without PTSD. Contrary to existing work, our preregistered analysis found little evidence for a difference in the hormonal profiles of warriors with high versus low PTSD symptom severity. Our results imply that the relationship between PTSD and hormonal diurnal variation may vary across populations and ecologies or that the association documented in Western populations stems from other correlated life factors.