Using your iPad or watching television late at night could make you depressed, according to a study that shows exposure to bright light during sleeping hours affects behaviour and stress levels.
American scientists found that mice regularly exposed to light at night became depressed – showing less interest in doing fun things, being less likely to explore new objects in their cages and not moving around as much. They also had higher levels of cortisol, the stress hormone.
Samer Hattar, professor of biology at Johns Hopkins University in the US, said: Basically, what we found is that chronic exposure to bright light – even the kind of light you experience in your own living room at home or in the workplace at night if you are a shift worker – elevates levels of a certain stress hormone in the body, which results in depression and lowers cognitive function.
He and his colleagues also found that the bright light affected special cells in the mices eyes, called intrinsically photosensitive retinal ganglion cells, which affect the part of the brain that manages mood, memory and learning.
Although the study was in mice, Prof Hattar said mice and men were similar in certain ways and so the study held lessons for people.
I’m not saying we have to sit in complete darkness at night, but I do recommend that we should switch on fewer lamps, and stick to less-intense light bulbs: Basically, only use what you need to see, he said.
A spokesman for Johns Hopkins: “When people routinely burn the midnight oil, they risk suffering depression and learning issues, and not only because of lack of sleep. The culprit could also be exposure to bright light at night from lamps, computers and even iPads.
The study is published in the journal Nature.
This article was first published in The Telgraph
By Stephen Adams
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