Chronic exposure to even dim levels of light at night can have
a significant unwanted effect on the ability to get a sound night's
sleep and a growing risk of depression, new research has
A study carried out by scientists at Ohio State University
revealed that in animals, being forced to sleep with a low level of
light as opposed to complete darkness led to the introduction of
depressive symptoms in subjects, such as lacking energy and
The research has now been linked to rising levels of depression
seen in the human population over the last 50 years.
Researchers connected the growing popularity of PCs, televisions
and other electronic devices in the bedroom as a key contributor to
individuals sleeping with low levels of light in the room.
The findings were based on two tests involving hamsters, whereby
half of subjects were exposed to a standard day-night cycle of
lighting - 16 hours of light and eight hours of complete darkness -
while a second group of animals had 16 hours of standard light
followed by eight hours of dim light conditions.
At the end of the four-week trial, the group exposed to chronic
dim light were found to be less interested in basic actions, such
as drinking, eating and a general lethargy in comparison to their
control group counterparts.
However, the study highlighted how these increased risk factors
could be counteracted by simply removing these unwanted night-time
stimuli and that within a few weeks of returning to a proper
day-night light cycle, all symptoms of depressive behaviour
disappeared in animal subjects.
Tracy Bedrosian, lead author of the study and doctoral student in
neuroscience at the university, said: "The good news is that people
who stay up late in front of the television and computer may be
able to undo some of the harmful effects just by going back to a
regular light-dark cycle and minimising their exposure to
artificial light at night. That's what the results we found in
hamsters would suggest."
Correlation between animal subjects and the human population are
possible due to the myriad studies that have been carried
concerning depression in people and the risk factors for the
development of this condition, with Ms Bedrosian noting: "The
results we found in hamsters are consistent with what we know about
depression in humans."
Following the experiment, the animals were humanely euthanised and
an area of their brain known as the hippocampus was studied. In
those animals exposed to dim light at night higher levels of a
protein known to be associated with tumour necrosis factor were
discovered, highlighting the impact of these protein levels on the
brain of these animals.
The studies were published in the journal Molecular
As a result, people wishing to improve their mood and become less
likely to develop depressive symptoms should ensure they sleep in
complete darkness and switch off electronic devices that could be
keeping them awake at night.
Marianne Davey, director of the British Snoring & Sleep Apnoea
Association, recently argued individuals should pay more attention
to getting the recommended amount of deep sleep, as it is during
these periods that the body releases hormones that allow cells and
tissues to repair themselves and grow.
As such, those who fail to achieve the recommended seven to eight
hours of sleep per night could begin to suffer from a range of
She commented: "Brain function suffers most from lack of sleep as
it reduces the capacity for decision making, impairs judgement,
affects memory and concentration.
"Physical consequences include headache and gastrointestinal
problems, and there is increasing evidence that there is a link
between lack of sleep and a higher risk of major illnesses such as
heart disease, diabetes, some cancers and obesity."
Posted by Michael Ewing