Featured Research

from universities, journals, and other organizations

Light at night causes changes in brain linked to depression

Date:
November 18, 2010
Source:
Ohio State University
Summary:
Exposure to even dim light at night is enough to cause physical changes in the brains of hamsters that may be associated with depression, a new study shows. Researchers found that female Siberian hamsters exposed to dim light every night for eight weeks showed significant changes in a part of the brain called the hippocampus.

Exposure to even dim light at night is enough to cause physical changes in the brains of hamsters that may be associated with depression, a new study shows.

Researchers found that female Siberian hamsters exposed to dim light every night for eight weeks showed significant changes in a part of the brain called the hippocampus.

This is the first time researchers have found that light at night, by itself, may be linked to changes in the hippocampus.

These alterations may be a key reason why the researchers also found that the hamsters exposed to dim light at night showed more depressive symptoms when compared to hamsters in a standard light-dark cycle.

"Even dim light at night is sufficient to provoke depressive-like behaviors in hamsters, which may be explained by the changes we saw in their brains after eight weeks of exposure," said Tracy Bedrosian, co-author of the study and doctoral student in neuroscience at Ohio State University.

Bedrosian and her colleagues presented the results Nov. 17 in San Diego at the annual meeting of the Society for Neuroscience.

The results are significant because the night-time light used in the study was not bright: 5 lux, or the equivalent of having a television on in a darkened room, said Randy Nelson, co-author of the study and professor of neuroscience and psychology at Ohio State.

"You would expect to see an impact if we were blasting these hamsters with bright lights, but this was a very low level, something that most people could easily encounter every night," said Nelson, who is also a member of Ohio State's Institute for Behavioral Medicine Research.

The study involved female Siberian hamsters, which had their ovaries removed to ensure that hormones produced in the ovary would not interfere with the results.

Half were housed in a standard light-dark cycle of 16 hours of light (at 150 lux) and eight hours of total darkness. The other half were housed in 16 hours of daylight (150 lux) and eight hours of dim light (5 lux).

After eight weeks in their lighting condition, they were tested for depressive-like behaviors. These tests are the same ones used by pharmaceutical companies to test anti-depressive and anti-anxiety drugs in animals before they are used in humans.

One depression test, for example, measured how much sugar water the mice drank. Mice generally like the drink, but those with depressive-like symptoms will not drink as much, presumably because they don't get as much pleasure from activities they usually enjoy.

Results showed that hamsters that lived in the dim light at night showed more symptoms of depression compared to the hamsters in the standard light-dark cycle.

At the end of the experiment, the researchers examined the hippocampus area of the hamsters' brains.

Results showed that mice that lived in the dim light had a significantly reduced density of dendritic spines -- hairlike growths on brain cells, which are used to send chemical messages from one cell to another.

"The hippocampus plays a key role in depressive disorders, so finding changes there is significant," Bedrosian said.

The researchers found no difference between the two groups of hamsters in terms of concentrations of the stress hormone cortisol. That's important because hormones like cortisol have been linked to changes in the hippocampus.

"To the best of our knowledge, this is the first study to document that light at night is a sufficient stimulus to induce changes in the hippocampus, without changes in cortisol levels," Nelson said.

How is light at night causing the changes in the hippocampus? The researchers believe it is related to production of the hormone melatonin. Light at night suppresses secretion of melatonin, which is involved in how the body knows it is nighttime.

The lower levels of melatonin at night may be the cause of the lower density of dendritic spines in the hippocampus, Bedrosian said.

The researchers are continuing this work by investigating the exact role of melatonin in the findings of this study.

These results are consistent with an earlier study by Nelson and his colleagues which found that constant bright light at night is linked to depressive symptoms in male mice. In another recent study, they found that light at night is also linked to weight gain in mice.

Other co-authors of the current study were Laura Fonken and James Walton, both graduate students at Ohio State.


Story Source:

The above story is based on materials provided by Ohio State University. The original article was written by Jeff Grabmeier. Note: Materials may be edited for content and length.


Cite This Page:

Ohio State University. "Light at night causes changes in brain linked to depression." ScienceDaily. ScienceDaily, 18 November 2010. <www.sciencedaily.com/releases/2010/11/101117184350.htm>.
Ohio State University. (2010, November 18). Light at night causes changes in brain linked to depression. ScienceDaily. Retrieved July 22, 2014 from www.sciencedaily.com/releases/2010/11/101117184350.htm
Ohio State University. "Light at night causes changes in brain linked to depression." ScienceDaily. www.sciencedaily.com/releases/2010/11/101117184350.htm (accessed July 22, 2014).

Share This




More Health & Medicine News

Tuesday, July 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Courts Conflicted Over Healthcare Law

Courts Conflicted Over Healthcare Law

AP (July 22, 2014) Two federal appeals courts issued conflicting rulings Tuesday on the legality of the federally-run healthcare exchange that operates in 36 states. (July 22) Video provided by AP
Powered by NewsLook.com
Why Do People Believe We Only Use 10 Percent Of Our Brains?

Why Do People Believe We Only Use 10 Percent Of Our Brains?

Newsy (July 22, 2014) The new sci-fi thriller "Lucy" is making people question whether we really use all our brainpower. But, as scientists have insisted for years, we do. Video provided by Newsy
Powered by NewsLook.com
Scientists Find New Way To Make Human Platelets

Scientists Find New Way To Make Human Platelets

Newsy (July 22, 2014) Boston scientists have discovered a new way to create fully functioning human platelets using a bioreactor and human stem cells. Video provided by Newsy
Powered by NewsLook.com
Gilead's $1000-a-Pill Drug Could Cure Hep C in HIV-Positive People

Gilead's $1000-a-Pill Drug Could Cure Hep C in HIV-Positive People

TheStreet (July 21, 2014) New research shows Gilead Science's drug Sovaldi helps in curing hepatitis C in those who suffer from HIV. In a medical study, the combination of Gilead's Hep C drug with anti-viral drug Ribavirin cured 76% of HIV-positive patients suffering from the most common hepatitis C strain. Hepatitis C and related complications have been a top cause of death in HIV-positive patients. Typical medication used to treat the disease, including interferon proteins, tended to react badly with HIV drugs. However, Sovaldi's %1,000-a-pill price tag could limit the number of patients able to access the treatment. TheStreet's Keris Lahiff reports from New York. Video provided by TheStreet
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins