A new study in medical students finds that summer, not winter, is the season when people are most likely to have higher levels of circulating stress hormones. These non-intuitive findings contradict traditional concepts of the taxing physical winter toll and the relaxed ease of summer.
Cortisol — often referred to as the "stress hormone" because it's released into the bloodstream in stressful situations — helps regulate sugar, salt and fluid levels in the body. The hormone helps reduce inflammation and is essential for maintaining overall health. Cortisol levels are usually highest in the morning and gradually decrease during the day. The level is lower in the evening to maintain a healthy sleep pattern. Illness, lack of sleep, and certain medications can affect cortisol levels more than normal daily fluctuations. Researchers from the University of Medical Sciences in Poland have now discovered seasonal patterns in the cortisol levels of medical students.
The research team studied a group of female medical students on two separate days in the winter and two days again in the summer. The researchers took saliva samples every two hours during each test period — a full 24-hour cycle — to measure levels of cortisol and markers of inflammation. During each testing session, the participants completed a survey about their sleep schedule, the type of diet they followed and their levels of physical activity.
Previous studies on the seasonal variability of cortisol have shown inconsistent results — possibly because participants were tested in their own homes and not in a uniform setting. However, in the current study, the research team found that cortisol levels were higher on the summer test dates. Inflammation levels did not change significantly between seasons.
