Scientists predict “optimal” body stress levels

Scientists have created an evolutionary model to predict how animals should react in stressful situations.

Almost all organisms have fast-acting stress responses, which help them respond to threats, but being stressed consumes energy and chronic stress can be harmful.

The new study, led by an international team that includes the University of Exeter, suggests that most animals remain stressed for longer than they are optimal after a stress-inducing accident.

The reasons for this are unclear, but one possibility is that there is a limit to how quickly the body can remove stress hormones from the circulation.

“We created one of the first mathematical models to understand how organisms evolved to deal with stressful events,” said Dr. Tim Fawcett, of the University of Exeter.

“It combines existing research on the physiology of stress in a variety of organisms with the analysis of optimal responses that balance the costs and benefits of stress.

“We know that stress responses vary enormously between different species and even between individuals of the same species, as we see in humans.

“Our study is a step towards understanding why stress responses are so variable.”

Researchers define stress as an organism’s process that responds to “stressors” (threats and challenges in their environment), including both sensing and responding to stress itself.

A key point highlighted in the study is the importance of how predictable the threats are.

The model suggests that an animal living in a dangerous environment should have a high “baseline” stress level, while an animal in a safer environment would benefit from the ability to raise and lower stress levels rapidly.

‘Our approach reveals environmental predictability and physiological limitations as key factors determining the evolution of stress responses,’ said lead author Professor Barbara Taborsky of the University of Bern.

“More research is needed to advance the scientific understanding of how this basic physiological system has evolved.”

The document, published in the journal Trends in ecology and evolution, is entitled: “Towards an Evolutionary Theory of Stress Responses”.