A groundbreaking study of medical students reveals that summer—not winter—triggers the highest levels of circulating stress hormones. These unexpected results challenge conventional wisdom about winter's harsh physical demands and summer's relaxing reprieve.
Cortisol, widely known as the "stress hormone," surges into the bloodstream during stressful times to regulate blood sugar, salt, and fluid balance. It also curbs inflammation and supports overall health. Levels naturally peak in the morning, tapering off through the day to promote restful sleep at night. Factors like illness, sleep deprivation, or medications can disrupt these rhythms more than daily variations. Researchers at Poland's University of Medical Sciences have uncovered clear seasonal patterns in cortisol among medical students.
The team examined female medical students over two full 24-hour days each in winter and summer. Saliva samples were collected every two hours to assess cortisol and inflammation markers. Participants also reported their sleep, diet, and exercise habits during testing.
Prior research on cortisol's seasonal fluctuations yielded mixed results, often due to home-based testing without controls. Here, in a standardized environment, summer days showed significantly elevated cortisol, while inflammation remained stable across seasons.
