Tuesday , June 22 2021

Do you have blue eyes? You tolerate the "winter deposit" better, says scientists – Novinky.cz

Thursday, April 11, 2019, 18:33

According to a 2014 survey, about 8 percent of Britons show signs of seasonal affective disorder and 21 signs of lighter disorder, only a kind of "winter depression."

What causes seasonal affective disorder?

But what causes seasonal affective disorder? Some theories claim that it is caused by the lack of sun during the winter. According to this theory, people in countries far from the equator, such as Iceland, should suffer more, but this has not been confirmed. Another theory says that the problem is circadian rhythms disturbed, which bothers the way the night extends in winter.

According to others, the problem is in the unbalanced levels of serotonin and melatonin in the body. Serotonin gives us energy, melatonin causes drowsiness. It is possible that a lot of melatonin forms in the body in people who suffer from a seasonal disorder, reason why they feel lethargic and tired.

There are many options in the game. It is possible that people susceptibility to seasonal disorder may be affected by the color of the eyes. A study of 175 students from two universities participated: one in South Wales and one in Cyprus. It has been found that people with clear eyes less often suffer from seasonal affective disorders than those with dark eyes. Different eyes can withstand different amounts of light.

Blue eyes are more sensitive to light

Light-sensitive cells are located in the retina of the human eye. When light enters the eye, these cells emit the nerve impulses that create the image in the brain. But in 1995, researchers found that some retinal cells do not participate in this process, but only send information to the hypothalamus on the clarity of the image. The hypothalamus is a very important part of the brain that releases hormones that regulate temperature, hunger and sleep cycle.

As the amount of blue and green light that reaches the hypothalamus increases, the level of melatonin decreases. The eyes with less pigment – blue or gray – are more sensitive to light. People with clear eyes release less melatonin in the fall and winter than in the dark. Therefore, it is possible that people with blue eyes are more resistant to seasonal affective disorder.

Why are there blue eyes in western populations living far from the equator? Some theories claim to be more attractive and therefore have a reproductive advantage. Or is that blue eyes are a side effect of the same mutation that causes a lighter skin color.

This mutation has been developed because it helps people to produce enough vitamin D even in places where the sun shines a bit in winter. Therefore, it is possible that pale people with bright eyes develop the ability to handle the lack of light in winter during the ages without falling into seasonal depression.

Of course, eye color is not the only factor in the development of seasonal affective disorder. It can also contribute to its development when people spend little time outside. These people are helped by outdoor paths, especially when the sun shines.

Phototherapy is also a relatively popular way of fighting winter in a bad mood and depression. All you need to do is sit in front of a full spectrum light for one hour a day and people show a considerable improvement. However, if the symptoms do not decrease, it does not even worsen, it is appropriate to see a doctor and consider using medications.

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