Stress is always bad for you, but new research suggests it damages your body more at night. For the study, participants completed a stress test either in the morning or in the evening. Everyone’s heart rate increased during the test, but cortisol levels only rose in people who took it in the a.m.
As counterintuitive as it may seem, the stress hormone’s absence at night is a bad sign, says study author Yujiro Yamanaka, Ph.D., associate professor of medicine at the Hokkaido University in Sapporo, Japan. When you’re in a stressful situation, your hypothalamic-pituitary-adrenal (HPA) axis, a hormonal response system to stress, triggers the release of cortisol to help your body manage the pressure.
At night, you have less cortisol in your system than you do in the morning because your circadian clock regulates the hormone, resulting in higher levels early in the day. When your body fails to release the hormone in the evening, it means you’re more susceptible to the negative health effects of stress.
Avoid evening stress by addressing issues in the morning when possible, lengthening your exhale, and minimizing artificial light from screens later in the day (which throws off your body clock and stresses the body), Yamanaka says. Nighttime workouts are safe, since physiological stress is different than the psychological type.
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