Exposure To Light At Night May Cause Depression

A new study reveals the possible negative effects of artificial light.

PSFK recently took note of the negative effects of nightly exposure to light as it pertains to gaining weight. Ohio State neuroscientist Tracy Bedrosian adds to this by arguing that prolonged exposure to light at night may cause depression.

In a controlled experiment, Bedrosian placed hamsters in one of two different environments. In the first environment, the hamsters spent 16 hours in daylight and then 8 hours in absolute darkness. The second group of hamsters still got 16 hours of daylight, but a dim light was placed in the 8-hour sleeping time.

Bedrosian then tested the hamsters for signs of depression and found that the hamsters that spent 8 hours in total darkness showed a clear preference for sugar water (hamsters typically prefer sweet treats) over regular water, while the hamsters that slept with a dim light showed no preference at all. The results imply that the latter group of hamsters are suffering from an inability to feel pleasure known as anhedonia, which is a key indicator of depression.

io9 further reports:

There were key differences in the brains of the two hamster groups. The hamsters that slept with the light had fewer dendritic spines, structures found near the hippocampus that are crucial for communication between brain cells. This ties in with human studies of depression that show the disease correlates with a shrinking of the hippocampus region.

Bedrosian suggests that these brain changes could be caused by a deficiency in the hormone melatonin. The hormone is essential in letting the body know that it’s nighttime, but nearby light sources can reduce its production. Other studies have revealed melatonin’s antidepressant qualities, which suggests a lack of it could spur on depression. This also fits neatly with studies demonstrating an increased risk of mood disorders for people who work at night.

Marie Claire: Sleeping with a Light on Can cause depression

[via io9]

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