The exigencies of modern life after paradise — relationships, finances, health — often trigger stress affecting the body’s serotonin system responsible for regulating mood, sleep, and appetite. Body temperature rises and the heart starts pumping faster as a “fight or flight” response to possible physical threats in the environment. Yet this stress-induced hyperthermia (SIH) may endure far beyond any practical purpose, developing into a chronic condition known as psychogenic fever characterized by extreme fatigue. A new study published in the journal Cell Metabolism uncovers the neural pathways associated with SIH that are likely linked to the chronic stress condition.

The new findings may soon lead to improved treatment for psychogenic fever, commonly treated with anxiolytic drugs including benzodiazepines, CRF receptor antagonists, and serotonergic ligands, according to researcher Kazuhiro Nakamura of Kyoto University in Japan.

"Many people with psychogenic fever, especially many teenagers, suffer from chronic increases in their body temperature that last more than a month," Nakamura said in a press release. "Our study revealed a fundamental central circuit mechanism underlying psychological stress-induced hyperthermia, and this mechanism may be important in understanding how psychogenic fever develops. It may also be important for designing clinical approaches to treat it."

In the study, Nakamura and his colleagues used a “social defeat stress test” in rats to induce a physiological response similar to that of human social stress. In the laboratory, they blocked inhibiting neurons in either the dorsomedial hypothalamus and the rostral medullary raphe, which effectively blocked heat production in brown fat tissue along with increases in body temperature otherwise caused by stress. Whereas white fat cells typically store calories, brown fat cells burn calories in an effect that produces heat with increased blood pressure and heart rate — the stress response observed in humans.

This basic stress response, SIH, has also been used by scientists to study the serotonin system in people with pre-clinical levels of chronic stress, illuminating a neurotransmitter system known famously as underlying causes of depression and anxiety disorders that plague the modern mind. Aside from causing severe discomfiture and limiting one’s enjoyment of life, chronic stress such as that brought by SIH may underly as many as 90 percent of visits to the doctor’s office, according to some researchers.

Although the body was designed to handle acute levels of stress, chronic stress conditions bringing high level of the hormone cortisol have been linked to the development of major chronic diseases such as obesity and diabetes, according to the Centers for Disease Control and Prevention.

Source: Kataoka et al. Psychological Stress Activates a Dorsomedial Hypothalamus-Medullary Raphe Neural Circuit to Drive Brown Adipose Tissue Thermogenesis and Hyperthermia. Cell Metabolism. 2014.