The stress hormone supports us in difficult circumstances in the morning, but in the evening it is no longer enough for this.
In response to stress, the level of stress hormones in our body increases. They are needed precisely in order to overcome difficult circumstances. For example, it is obvious that stress requires additional energy expenditure – and the stress hormone cortisol acts on the metabolism in order to obtain this energy. But at the same time, cortisol obeys circadian rhythms, and without any stress, its level rises in the morning and decreases in the evening.
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In an article in Neuropsychopharmacology Reports, researchers from Hokkaido University write that because cortisol follows the body clock, our bodies may respond less well to evening stress than to morning stress. The experiment involved 27 volunteers with a normal daily routine, whose diurnal changes in cortisol levels were first measured and then divided into two groups: one had to undergo a stressful task in the morning, the other in the evening.
The task took 15 minutes and consisted of preparing a presentation and presenting it to three interviewers on camera; In addition, I had to solve an arithmetic problem in my head. The hormone level was measured before the task, immediately after it, and then several more times within half an hour.
It turned out that cortisol rose significantly from stress in those who completed the task in the morning, but not in those who completed it in the evening. Apparently, the circadian rhythm mechanism prohibited the release of additional amounts of the hormone, despite stress. On the other hand, not only the hormonal system reacts to stress, but also the nervous system, which can be judged, for example, by the heart rate: under stress, the autonomic nervous system makes the heart beat faster. The “evening” and “morning” participants in the experiment had the same heart beat, that is, the reaction of the nervous system did not depend on the time of day.
Since the evening stress response is incomplete, it can be assumed that it is more difficult for the body to cope with it – as was said, cortisol mobilizes energy resources, but if there is not enough cortisol, how then to get energy for stress? Since the lion’s share of psychological stress happens to us due to some work-related matters, this is another argument in favor of the fact that it is better not to work in the evening, but to relax. On the other hand, let’s not forget that chronotypes differ among different people, and sometimes quite strongly (we once already wrote that there are many varieties among “owls” and “larks”). So, perhaps some people have enough evening cortisol to deal with stress.