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From VOA Learning English, |
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this is the Health Report. |
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Some colors that people see |
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late at night could cause signs |
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of the condition mental health experts call |
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clinical depression. |
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That was the finding of a study |
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that builds on earlier study findings. |
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They show that individuals |
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who live or work in low levels of light overnight |
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can develop clinical depression. |
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Doctors use the words clinical depression |
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to describe severe form of depression. |
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Signs may include loss of interest |
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or pleasure in most activities, |
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low energy levels and thoughts of death or suicide. |
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In the new study, |
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American investigators designed an experiment |
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that exposed hamsters to different colors. |
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The researchers chose hamsters |
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because they are nocturnal, |
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which means they sleep during the day |
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and are active at night. |
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The animals were separated into 4 groups. |
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One group of hamsters was kept in the dark |
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during their nighttime period. |
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Another group was placed in foldable blue light, |
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a third group slept in foldable white light. |
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While a fourth was put in foldable red light. |
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After four weeks, the researchers noted |
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how much sugary water the hamsters drank. |
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They found that the more depressed animals |
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drank the least amount of water. |
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Randy Nelson heads the Department of Neuroscience |
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at Ohio State University. |
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He says animals that slept in blue and white light |
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appeared to be the most depressed. |
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"What we saw is these animals didn't show |
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any sleep disruptions at all |
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but they did have mucked up circadian clock genes |
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and they did show depressive phenotypes |
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whereas if they were in the dim red light, they did not." |
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Randy Nelson notes |
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that photosensitive cells in the retina, |
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have little to do with eyesight. |
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He says these cells send signals |
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to the area of the brain that controls |
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what has been called the natural sleep-wake cycle. |
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He says there's a lot of blue in white light, |
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this explains why the blue light and white light hamsters |
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appear to be more depressed |
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than the hamsters see red light or darkness. |
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Mr Nelson has suggestions |
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for people who work late at night, |
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or those who like to stay up late. |
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"My recommendation is |
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if you are just living a typical |
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during the day, |
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mostly inactive at night, |
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you want to limit exposure to TVs which are quite bluish |
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in the light they give off |
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and computer screens and things like that. |
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You can get filtered glass, |
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you can get filters on your computer screen |
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and filters on your eReaders |
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to put it more in the reddish light." |
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The report on the effects of light on emotions |
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was published in The Journal of Neuroscience. |
