The findings, from laboratory studies, were presented at a poster session Tuesday, Nov. 15, during the annual meeting of the Society for Neuroscience in Washington, D.C.
"It's generally understood that females respond more strongly to acute (immediate, short-term) stress than males," said Helmer Figueiredo, PhD, of UC's department of psychiatry. "Our research shows that this may also be the case in more clinically relevant chronic-stress conditions."
Dr. Figueiredo, a research assistant professor at UC, and his colleagues studied stress response in male and female rats during a 15-day period.
They noticed markedly increased levels of the stress hormone corticosterone in the female rats compared with males.
The major glucocorticoid (or steroid hormone) in rats, corticosterone, is produced by the adrenal glands in response to stress. In humans, the major glucocorticoid is called cortisol.
The adrenal glands, together with the pituitary and hypothalamus, make up the "stress axis." When an organism experiences stress, higher levels of glucocorticoids are produced to aid in survival and recovery. But prolonged high levels of this hormone can have negative health effects, such as increased abdominal obesity and decreased immune response.
"Stress is an important part of life," said Dr. Figueiredo. "In fact, it has been said that 'life is stress.'
"When appropriately handled by the body, stress can have beneficial implications in preparing the organism for the 'fight or flight' response. However, under intense chronic conditions, when extreme levels of glucocorticoid are produced, stress can seriously harm the body."
Chronic stress, especially unpredictable chronic stress, has been implicated in the development of a wide number of diseases in humans, ranging from mental illness to autoimmune and cardiovascular diseases.
"Serious disorders such as major depression, anxiety and autoimmune dysfunctions, all linked to higher levels of circulating glucocorticoids, are more prevalent among women than men," said co-author James Herman, PhD, professor and stress neurobiologist in UC's psychiatry department. "This animal research provides a nice link between chronic stress and the physiological response to stress by females," he said.
The next step, said Dr. Figueriedo, is to determine the specific roles of sex hormones and the menstrual cycle in chronic-stress response.
"Understanding how the stress response is handled differently between males and females is a major goal for the development of 'female-sensitive' drugs," said Dr. Figueriedo.