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Stress Hormones Underlie Indigenous Health Gap

James Cook University scientists have found that secretion of the stress hormone cortisol is impaired in young Indigenous adults, and that their biological stress response is linked to the racial discrimination they experience.

The study, published in Scientific Reports, showed for the first time that the morning increase of cortisol that prepares us to effectively deal with the stresses of the upcoming day is missing in otherwise healthy young Indigenous adults.

Prof Zoltan Sarnyai of JCU’s Australian Institute of Tropical Health and Medicine explained that cortisol concentration in the blood should be within a certain range. “Too little or too much of it is dangerous for health,” he said. “We can’t tell why it is low in this case.

“One possible explanation is that previous stress, early traumatic events or even traumas of the past generation may have impaired the negative feedback system, so the brain and the body feel as if there is too much cortisol around. So it shuts off its own cortisol production after awakening.”

The absence of the morning cortisol rise was related to the levels of chronic stress the participants had experienced. Patients with common and severe mental disorders, including depression and psychotic disorders, are similarly missing such a morning rise.

The study’s first author, Dr Maximus Berger, said there is evidence that the missing morning rise of cortisol indicates a risk of poor mental health in the future. This raises the possibility of using this measure to study the risk of future mental health problems in young Indigenous Australians and other First Nations people worldwide.

Berger and his colleagues found that the hormonal stress response was blunted in Indigenous participants who reported high levels of internalised racism (the acceptance of ethnic stereotypes relating to members of one’s own group), which points towards a link between discrimination and an inadequate response to stress.

Sarnyai said it is highly unlikely that the observed abnormalities are due to genetic factors, since the non-Indigenous control group was comprised of an ethnically diverse group of individuals.

However, this study cannot rule out that epigenetic changes – the process by which a gene is switched on or off without changing the DNA code – caused by early experiences and even by transgenerational traumas might play a role.

Sarnyai said the study could open up a new avenue to predict the development of mental health problems in First Nations people. “It may allow us in the future to objectively monitor efficacy of programs and policies to reduce the Indigenous health gap,” he said.