| [00:00.10] |
From VOA Learning English, |
| [00:03.52] |
this is the Health Report. |
| [00:05.29] |
Some colors that people see |
| [00:08.75] |
late at night could cause signs |
| [00:11.56] |
of the condition mental health experts call |
| [00:15.18] |
clinical depression. |
| [00:16.87] |
That was the finding of a study |
| [00:20.16] |
that builds on earlier study findings. |
| [00:23.03] |
They show that individuals |
| [00:26.08] |
who live or work in low levels of light overnight |
| [00:31.00] |
can develop clinical depression. |
| [00:33.51] |
Doctors use the words clinical depression |
| [00:37.67] |
to describe severe form of depression. |
| [00:41.80] |
Signs may include loss of interest |
| [00:45.22] |
or pleasure in most activities, |
| [00:47.51] |
low energy levels and thoughts of death or suicide. |
| [00:53.04] |
In the new study, |
| [00:55.46] |
American investigators designed an experiment |
| [00:59.58] |
that exposed hamsters to different colors. |
| [01:03.06] |
The researchers chose hamsters |
| [01:06.36] |
because they are nocturnal, |
| [01:08.42] |
which means they sleep during the day |
| [01:11.35] |
and are active at night. |
| [01:13.81] |
The animals were separated into 4 groups. |
| [01:18.60] |
One group of hamsters was kept in the dark |
| [01:22.81] |
during their nighttime period. |
| [01:25.38] |
Another group was placed in foldable blue light, |
| [01:30.15] |
a third group slept in foldable white light. |
| [01:34.28] |
While a fourth was put in foldable red light. |
| [01:38.99] |
After four weeks, the researchers noted |
| [01:43.76] |
how much sugary water the hamsters drank. |
| [01:47.08] |
They found that the more depressed animals |
| [01:51.19] |
drank the least amount of water. |
| [01:54.00] |
Randy Nelson heads the Department of Neuroscience |
| [01:58.77] |
at Ohio State University. |
| [02:01.53] |
He says animals that slept in blue and white light |
| [02:06.36] |
appeared to be the most depressed. |
| [02:09.62] |
"What we saw is these animals didn't show |
| [02:12.24] |
any sleep disruptions at all |
| [02:13.64] |
but they did have mucked up circadian clock genes |
| [02:17.42] |
and they did show depressive phenotypes |
| [02:22.05] |
whereas if they were in the dim red light, they did not." |
| [02:24.71] |
Randy Nelson notes |
| [02:26.31] |
that photosensitive cells in the retina, |
| [02:29.53] |
have little to do with eyesight. |
| [02:32.65] |
He says these cells send signals |
| [02:36.92] |
to the area of the brain that controls |
| [02:40.29] |
what has been called the natural sleep-wake cycle. |
| [02:44.70] |
He says there's a lot of blue in white light, |
| [02:49.13] |
this explains why the blue light and white light hamsters |
| [02:54.69] |
appear to be more depressed |
| [02:58.03] |
than the hamsters see red light or darkness. |
| [03:02.36] |
Mr Nelson has suggestions |
| [03:06.31] |
for people who work late at night, |
| [03:09.03] |
or those who like to stay up late. |
| [03:12.28] |
"My recommendation is |
| [03:13.96] |
if you are just living a typical |
| [03:16.34]mostly active [life] |
during the day, |
| [03:18.30] |
mostly inactive at night, |
| [03:19.42] |
you want to limit exposure to TVs which are quite bluish |
| [03:23.64] |
in the light they give off |
| [03:24.98] |
and computer screens and things like that. |
| [03:27.43] |
You can get filtered glass, |
| [03:29.09] |
you can get filters on your computer screen |
| [03:30.95] |
and filters on your eReaders |
| [03:32.16] |
to put it more in the reddish light." |
| [03:34.86] |
The report on the effects of light on emotions |
| [03:38.72] |
was published in The Journal of Neuroscience. |