Depression by dim light during the night

Darkness during the night protects against depression

07/24/2012

Darkness during the night has a preventative effect on depression. This is the result of a study by US researchers at Ohio State University in Columbus. The scientists found that the artificial lighting during the night has a very unfavorable effect on the psyche.

In an experiment with hamsters, the US researchers around Dr. med. Randy Nelson from the Department of Neuroscience at Ohio State University shows that artificial lighting during the night significantly increases the risk of depression, and conversely, darkness can prevent and even alleviate depression.

Experiments with hamsters show negative effects of nocturnal illumination
„Exposure to artificial lighting at night has risen sharply over the past 50 years, coinciding with rising rates of depression“ The US scientists explain in the magazine „Molecular Psychiatry“ the approach of her research. As part of her study, Dr. Nelson and fellow female Siberian hamsters sleep exclusively in dim light for four weeks. In order to exclude hormonal effects, the hamsters were removed before attempting the ovaries. One group of animals was exposed to light of 150 lux during the day for 16 hours during the day for 16 hours, and five lux lux for eight hours at night, which is similar to the light a TV sets in a dark room. After the first four weeks of trial run, the hamsters slept again for one, two or four weeks in the dark. As a control group served hamsters who lived for eight weeks in a normal day-night rhythm of 16 hours at 150 lux and eight hours of darkness.

Nocturnal lighting makes hamsters depressed
While the hamsters with normal day-night rhythm showed no signs of mental discomfort, the animals that slept in twilight at night showed clearly depression-like symptoms after the first four weeks. Nelson and colleagues. The hamster females were less active and also showed a lower interest in sugar water, which is rated in the animals as depressive behavior, so the statement of the US researchers. When the hamsters subsequently went back to darkness, the depressive symptoms receded after two weeks of normal daytime rhythm. The animals showed again the usual joie de vivre and a corresponding appetite for sugar water. Decisive for the effect of nocturnal twilight on the psyche was, according to the scientists, the so-called tumor necrosis factor. When illuminated at night, this molecule is increasingly released and causes the development of depressive symptoms in the brain Nelson and colleagues.

Dim light during the night cause of various diseases
From earlier studies it was already known that „Chronic exposure to nocturnal illumination is associated with an increased risk of breast cancer, obesity, and mood swings“ is, the US scientists report in the journal „Molecular Psychiatry“. However, it was unclear how the twilight affects the psyche. In the experiments with hamsters, the first indications of the negative effect of nocturnal lighting have now emerged. The researchers suspect that in humans comparable effects of twilight are to be expected as in the hamsters. A running TV, the alarm clock, or a street light shining into the bedroom would increase the risk of depression.

Darkness to relieve depression
Fortunately, according to the US researchers, the negative influence of twilight can also be reversed if darkness is respected at night. In addition, the results of the US researchers suggest that depression may be generally alleviated by sufficient darkness during the night. However, this is increasingly difficult to ensure, especially since in the cities, the nighttime light pollution (lightening of the night sky by artificial light sources) has already taken an enormous form. But not only the surplus of light can have consequences for the psyche, also lack of light carries some risks, since the sunlight is needed for example for the production of vitamin D. Also, a deficit of light is considered a major risk factor for winter depression. (Fp)

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Picture credits: Andreas Dengs, www.photofreaks.ws