Too Much Light at Night Could Negatively Impact Mood

As we enter the colder months, a lot of people get blue from the lack of sunlight that occurs during this season. Scientists from John Hopkins University set out to better understand the effects of depression on mice in the hopes that it would tell them something about how the disorder impacts humans. After exposing the mice to alternating 3.5 hour cycles of light and darkness, with light being shown on the animals as they slept, it was determined that the mice became depressed. One study author, Samer Hattar, advised that the mice exhibited signs of depression such as lack of interest in food, lower activity levels, and impaired thinking. Further, all symptoms of depression dissipated when the mice were given the anti-depressant Prozac. As a side discovery, scientists uncovered that exposing the intrinsically photosensitive retinal ganglion cells (ipRGCs) in mice’s eyes to bright light at night is what affected their mood, memory, and cognitive functioning. Humans also have similar light-sensitive cells. According to an article found at US News online, repeated exposure to bright conditions at night when the body is in a resting state can result in an overproduction of the stress hormone, cortisol. Cortisol has been linked to depression and poor cognitive functioning. The implication of the study is that being exposed to bright light at night – even that of computers or television – might not be good for one’s mental health. While not all results occurring in mice can be directly applied to people, the animal model does help us determine what outcomes warrant further human testing.

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