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