Posts Tagged Ohio State University

Light At Night Damage May Be Reversed


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Main Category: Depression
Also Included In: Psychology / Psychiatry;  Neurology / Neuroscience
Article Date: 26 Jul 2012 – 10:00 PDT

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Light At Night Damage May Be Reversed

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A new study, published online in the journal Molecular Psychiatry, has revealed that although chronic exposure to dim light at night can lead to depressive symptoms in rodents, the symptoms are reversible by simply switching back to a normal light-dark cycle.

Researchers found that hamsters that were exposed to 4 weeks of light during the dark cycle at night displayed symptoms of depression, which disappeared around two weeks, after switching back to a normal day and night cycle. The researchers noted that changes in the hamsters brain, which occurred during the chronic light period, also reversed when they returned to a normal light cycle.

Leading researcher, Tracy Bedrosian, a doctoral student in neuroscience at Ohio State University, says that these study results add to existing evidence that chronic exposure to artificial light at night may have an influence on the growing rates of depression in humans during the past 5 centuries, adding: “The results we found in hamsters are consistent with what we know about depression in humans.”

The new study also offers some hope for those suffering from depression.

Bedrosian explained:

“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 minimizing their exposure to artificial light at night. That’s what the results we found in hamsters would suggest.”

The study was a collaboration of Bedrosian, Zachary Weil, research assistant professor in neuroscience and Randy Nelson, professor of neuroscience and psychology, whose lab conducted previous studies in which he linked chronic exposure to light at night to depression and obesity in animal models.

The team discovered that one particular protein called tumor necrosis factor (TNF) that is present in the brain of hamsters, which is also present in humans, may play a key part in exposure to light at night can lead to depression. By blocking this protein, the team managed to prevent the hamsters from developing depressive-like symptoms – even when they were exposed to light at night.

The researchers conducted two experiments with female Siberian hamsters – with surgically removed ovaries – to ensure that the results were not distorted due to the production of hormones.

The first experiment exposed half of the hamsters to eight weeks in a standard light-dark cycle of 16 hours of light (150 lux) and 8 hours of total darkness each day, whilst the other hamsters were kept in 16 hours of daylight and 8 hours of dim light, i.e. 5 lux, for the first four weeks, which is similar to an on-switched television in a darkened room.

After eight weeks, the hamsters were returned to live under normal light cycle conditions for a period of either 1,2 or 4 weeks before testing began.

The animals were subsequently subjected to various behavior tests, which showed that hamsters exposed to chronic dim light at night were less active overall during their active period each day than those in standard lighting conditions.

The animals that experienced the dim light also displayed greater depressive symptoms compared with the other hamsters, which was observed by showing less interest in drinking sugar water they usually enjoy. However, the team observed that within two weeks of returning to a normal light cycle, the depressive-like symptoms in those in the dim light group were no different than that in hamsters that always had standard lighting and that the animals regained their normal levels of activity. The animals were sacrificed after the behavioral test and the researchers examined the animals’ hippocampus, the region in the brain that plays a key role in depressive disorders. The team discovered that the hippocampus of those that were exposed to dim light displayed various changed linked to depression, one of which was an increased expression of the gene that produces TNF.

TNF is a chemical messenger, which is activated during an injury or infection. It belongs to a large family of proteins called cytokines, which cause inflammation in an effort to repair the body’s injured or infected site. However, when the inflammation is constant it can be damaging, as seen in the hamsters that were exposed to dim light at night.

Nelson, who is a member of Ohio State’s Institute for Behavioral Medicine Research stated: “Researchers have found a strong association in people between chronic inflammation and depression. That’s why it is very significant that we found this relationship between dim light at night and increased expression of TNF.”

The team also discovered that hamsters in the dim light group had a considerably reduced density of dendritic spines, i.e. hair like growths on brain cells that transmit chemical messages between cells. Bedrosian stated that changes such as this have been associated with depression.

The team did discover though that in hamsters that were returned to a regular light-dark cycle after four weeks of dim light during the night were able to restore their TNF levels and even their density of dendritic spines to essentially normal levels.

Bedrosian commented: “Changes in dendritic spines can happen very rapidly in response to environmental factors.”

The second experiment involved testing TNFs importance in causing the negative effects those hamsters that were exposed to light at night. Some hamsters received a drug named XPro1595, a TNF inhibitor that negates the effects of some forms of TNF in the brain. The results demonstrated that those in the dim light group displayed no more depressive-like symptoms than standard-light hamsters if they were given XPro1595. The team points out that the drug was not able to prevent the reduction of dendritic spine density in those exposed to dim light.

Nelson concludes that these results add to existing evidence of TNFs potential role in causing depressive symptoms in hamsters exposed to dim light. He continues saying that the fact that XPro1595 did not affect dendritic spine density means that more research is necessary to gain further insight into the workings of TNF.

Written by Petra Rattue
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

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Please use one of the following formats to cite this article in your essay, paper or report:

MLA

Petra Rattue. “Light At Night Damage May Be Reversed.” Medical News Today. MediLexicon, Intl., 26 Jul. 2012. Web.
26 Jul. 2012. <http://www.medicalnewstoday.com/articles/248328.php&gt;


APA

Petra Rattue. (2012, July 26). “Light At Night Damage May Be Reversed.” Medical News Today. Retrieved from
http://www.medicalnewstoday.com/articles/248328.php.

Please note: If no author information is provided, the source is cited instead.


‘Light At Night Damage May Be Reversed’

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Minimizing Exposure To Artificial Light At Night May Improve Depressive Symptoms


Main Category: Depression
Also Included In: Public Health;  Psychology / Psychiatry;  Obesity / Weight Loss / Fitness
Article Date: 26 Jul 2012 – 0:00 PDT

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Minimizing Exposure To Artificial Light At Night May Improve Depressive Symptoms

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Chronic exposure to dim light at night can lead to depressive symptoms in rodents — but these negative effects can be reversed simply by returning to a standard light-dark cycle, a new study suggests.

While hamsters exposed to light at night for four weeks showed evidence of depressive symptoms, those symptoms essentially disappeared after about two weeks if they returned to normal lighting conditions.

Even changes in the brain that occurred after hamsters lived with chronic light at night reversed themselves after returning to a more normal light cycle.

These findings add to the growing evidence that suggest chronic exposure to artificial light at night may play some role in the rising rates of depression in humans during the past 50 years, said Tracy Bedrosian, lead author of the study and doctoral student in neuroscience at Ohio State University.

“The results we found in hamsters are consistent with what we know about depression in humans,” Bedrosian said.

But the new study, published online in the journal Molecular Psychiatry, also offers some hope.

“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 minimizing their exposure to artificial light at night,” Bedrosian said. “That’s what the results we found in hamsters would suggest.”

Bedrosian conducted the study with Ohio State colleagues Randy Nelson, professor of neuroscience and psychology, and Zachary Weil, research assistant professor in neuroscience.

This study is the latest in a series out of Nelson’s lab that have linked chronic exposure to light at night to depression and obesity in animal models.

The new study found that one particular protein found in the brain of hamsters — and humans — may play a key role in how light at night leads to depression.

They found that blocking effects of that protein, called tumor necrosis factor, prevented the development of depressive-like symptoms in hamsters even when they were exposed to light at night.

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

In the first experiment, half of the hamsters spent eight weeks in a standard light-dark cycle of 16 hours of light (150 lux) and 8 hours of total darkness each day. The other half spent the first four weeks with 16 hours of normal daylight (150 lux) and 8 hours of dim light — 5 lux, or the equivalent of having a television on in a darkened room.

Then, these hamsters were moved back to a standard light cycle for either one week, two weeks or four weeks before testing began.

They were then given a variety of behavior tests. Results showed that hamsters exposed to chronic dim light at night showed less total activity during their active period each day when compared to those in standard lighting conditions.

Those hamsters exposed to dim light also showed greater depressive symptoms than did the others– such as less interest in drinking sugar water that they usually enjoy.

But within two weeks of returning to a standard light cycle, hamsters exposed to dim night light showed no more depressive-like symptoms than did hamsters that always had standard lighting. In addition, they returned to normal activity levels.

After the behavioral testing, the hamsters were sacrificed and the researchers studied a part of their brains called the hippocampus, which plays a key role in depressive disorders. Findings showed that hamsters exposed to dim light showed a variety of changes associated with depression.

Most importantly, hamsters that lived in dim light showed increased expression of the gene that produces tumor necrosis factor. TNF is one of a large family of proteins called cytokines — chemical messengers that are mobilized when the body is injured or has an infection. These cytokines cause inflammation in their effort to repair an injured or infected area of the body. However, this inflammation can be damaging when it is constant, as happens in hamsters exposed to dim light at night.

“Researchers have found a strong association in people between chronic inflammation and depression,” said Nelson, who is a member of Ohio State’s Institute for Behavioral Medicine Research.

“That’s why it is very significant that we found this relationship between dim light at night and increased expression of TNF.”

In addition, results showed that hamsters that lived in 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.

Changes such as this have been linked to depression, Bedrosian said.

However, hamsters that were returned to a standard light-dark cycle after four weeks of dim light at night saw their TNF levels and even their density of dendritic spines return essentially to normal.

“Changes in dendritic spines can happen very rapidly in response to environmental factors,” Bedrosian said.

In a second experiment, the researchers tested just how important TNF might be in causing the negative effects seen in hamsters exposed to light at night. In this experiment, some hamsters were given a drug called XPro1595, which is a TNF inhibitor — meaning that it negates the effects of some forms of TNF in the brain.

Results showed that hamsters exposed to dim light at night did not show any more depressive-like symptoms than standard-light hamsters if they were given XPro1595. However, the drug did not seem to prevent the reduction of dendritic spine density in hamsters exposed to dim light.

These results provide further evidence of the role TNF may play in the depressive symptoms seen in hamsters exposed to dim light. But the fact that XPro1595 did not affect dendritic spine density means that more needs to be learned about exactly how TNF works, Nelson said.

Article adapted by Medical News Today from original press release. Click ‘references’ tab above for source.
Visit our depression section for the latest news on this subject.
Written by Jeff Grabmeier
The study was supported by grants from the National Science Foundation and the U.S. Department of Defense. The XPro1595 used in the study was provided by Xencor, Inc.
Ohio State University
Please use one of the following formats to cite this article in your essay, paper or report:

MLA

Ohio State University. “Minimizing Exposure To Artificial Light At Night May Improve Depressive Symptoms.” Medical News Today. MediLexicon, Intl., 26 Jul. 2012. Web.
26 Jul. 2012. <http://www.medicalnewstoday.com/releases/248225.php&gt;


APA

Ohio State University. (2012, July 26). “Minimizing Exposure To Artificial Light At Night May Improve Depressive Symptoms.” Medical News Today. Retrieved from
http://www.medicalnewstoday.com/releases/248225.php.

Please note: If no author information is provided, the source is cited instead.

Contact Our News Editors

For any corrections of factual information, or to contact the editors please use our feedback form.

Please send any medical news or health news press releases to:

Note: Any medical information published on this website is not intended as a substitute for informed medical advice and you should not take any action before consulting with a health care professional. For more information, please read our terms and conditions.

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Keep the TV or Computer on At Night? You’re at Greater Risk for Depression


Keep the TV or Computer on At Night? You are at Greater Risk for DepressionIf hamsters are anything like their human counterparts, keeping your TV or computer on at night while you sleep in the same room could not only disrupt your sleep — it could lead to clinical depression.

Any kind of light in your bedroom — a streetlight, a TV, likely even a nightlight — may lead to the depressive symptoms, if exposed to such light for at least a month.

While hamsters exposed to light at night for four weeks showed evidence of depressive symptoms, those symptoms essentially disappeared after about two weeks if they returned to normal lighting conditions.

Even changes in the brain that occurred after hamsters lived with chronic light at night reversed themselves after returning to a more normal light cycle.

These findings add to the growing evidence that suggest chronic exposure to artificial light at night may play some role in the rising rates of depression in humans during the past 50 years, said Tracy Bedrosian, lead author of the study and doctoral student in neuroscience at Ohio State University.

The good news is that the effects of sleep loss are readily reversed with some normal, completely-dark sleep. Use your TV’s sleep timer function to turn it off after you go to sleep. Shut down your computer before going to bed.

This study is the latest in a series out of Nelson’s lab that have linked chronic exposure to light at night to depression and obesity in animal models.

The new study found that one particular protein found in the brain of hamsters — and humans — may play a key role in how light at night leads to depression.

They found that blocking effects of that protein, called tumor necrosis factor, prevented the development of depressive-like symptoms in hamsters even when they were exposed to light at night.

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

In the first experiment, half of the hamsters spent eight weeks in a standard light-dark cycle of 16 hours of light (150 lux) and 8 hours of total darkness each day. The other half spent the first four weeks with 16 hours of normal daylight (150 lux) and 8 hours of dim light — 5 lux, or the equivalent of having a television on in a darkened room.

Then, these hamsters were moved back to a standard light cycle for either one week, two weeks or four weeks before testing began.

They were then given a variety of behavior tests. Results showed that hamsters exposed to chronic dim light at night showed less total activity during their active period each day when compared to those in standard lighting conditions.

Those hamsters exposed to dim light also showed greater depressive symptoms than did the others– such as less interest in drinking sugar water that they usually enjoy.

But within two weeks of returning to a standard light cycle, hamsters exposed to dim night light showed no more depressive-like symptoms than did hamsters that always had standard lighting. In addition, they returned to normal activity levels.

After the behavioral testing, the hamsters were sacrificed and the researchers studied a part of their brains called the hippocampus, which plays a key role in depressive disorders.

Findings showed that hamsters exposed to dim light showed a variety of changes associated with depression.

Most importantly, hamsters that lived in dim light showed increased expression of the gene that produces tumor necrosis factor. TNF is one of a large family of proteins called cytokines — chemical messengers that are mobilized when the body is injured or has an infection. These cytokines cause inflammation in their effort to repair an injured or infected area of the body. However, this inflammation can be damaging when it is constant, as happens in hamsters exposed to dim light at night.

“Researchers have found a strong association in people between chronic inflammation and depression,” said Nelson, who is a member of Ohio State’s Institute for Behavioral Medicine Research.

“That’s why it is very significant that we found this relationship between dim light at night and increased expression of TNF.”

In addition, results showed that hamsters that lived in 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.

Changes such as this have been linked to depression, Bedrosian said.

However, hamsters that were returned to a standard light-dark cycle after four weeks of dim light at night saw their TNF levels and even their density of dendritic spines return essentially to normal.

“Changes in dendritic spines can happen very rapidly in response to environmental factors,” Bedrosian said.

In a second experiment, the researchers tested just how important TNF might be. Results showed that hamsters exposed to dim light at night did not show any more depressive-like symptoms than standard-light hamsters if they were given XPro1595. However, the drug did not seem to prevent the reduction of dendritic spine density in hamsters exposed to dim light.

These results provide further evidence of the role TNF may play in the depressive symptoms seen in hamsters exposed to dim light. But the fact that XPro1595 did not affect dendritic spine density means that more needs to be learned about exactly how TNF works, Nelson said.

Source: Ohio State University

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Sad Movies Make Many People Happy


Sad Movies Make Many People Happy | Psych Central News

Sad Movies Make Many People Happy
By RICK NAUERT PHD Senior News Editor
Reviewed by John M. Grohol, Psy.D. on March 28, 2012
New research helps explains why many people enjoy watching tragic movies or plays. Apparently, the emotional connection evoked by such stories helped viewers better appreciate their own close relationships, which in turn boosted their life happiness.

Thus, the paradox is that what seems like a negative experience — watching a sad story — can make people happier by bringing attention to some positive aspects in their own lives.

Tragic stories often focus on themes of eternal love, and this leads viewers to think about their loved ones and count their blessings,” said Silvia Knobloch-Westerwick, Ph.D., lead author of the study.

Researchers found movies that cause a viewer to think about their own situation and relationships are powerful.

Investigators found that the more an individual thought about their loved ones during the movie — in this case, the 2007 film “Atonement,” based on the award-winning novel by Ian McEwan — the greater the increase in their happiness.

However, viewers who had self-centered thoughts concerning the movie — such as “My life isn’t as bad as the characters in this movie” — did not see an increase in their happiness.

Knobloch-Westerwick said this study is one of the first to take a scientific approach to explaining why people enjoy fictional tragedies that make them sad.

“Philosophers have considered this question over the millennia, but there hasn’t been much scientific attention to the question,” she said.

Researchers studied 361 college students who viewed an abridged version of  “Atonement,” which involves two lovers who are separated and die as war casualties. Before and after viewing the movie, the respondents were asked several questions which measured how happy they were with their life.

They were also asked before, after and three times during the movie to rate how much they were feeling various emotions, including sadness.

After the movie, participants rated how much they enjoyed the movie and wrote about how the movie had led them to reflect on themselves, their goals, their relationships and life in general.

What people wrote about as a result of seeing the movie was a key in understanding why people enjoy viewing fictional tragedies, Knobloch-Westerwick said. People who experienced a greater increase in sadness while watching the movie were more likely to write about real people with whom they had close relationships, she said.

This in turn, increased participants’ life happiness after viewing, which was then related to more enjoyment of the movie.

“People seem to use tragedies as a way to reflect on the important relationships in their own life, to count their blessings,” she said. “That can help explain why tragedies are so popular with audiences, despite the sadness they induce.”

Surprisingly, the perception that movies may make people feel more happiness because they compare themselves to the characters portrayed and feel good that their own lives are not as bad — was not the case.

People whose thoughts after the movie were about themselves — rather than about their close relationships — did not experience an increase in life happiness.

“Tragedies don’t boost life happiness by making viewers think more about themselves. They appeal to people because they help them to appreciate their own relationships more,” she said.

But why would people have to get sad by watching a tragedy to feel grateful about relationships in their own lives? Knobloch-Westerwick said this fits with research in psychology that suggests negative moods make people more thoughtful.

Positive emotions are generally a signal that everything is fine, you don’t have to worry, you don’t have to think about issues in your life,” she said.

“But negative emotions, like sadness, make you think more critically about your situation. So seeing a tragic movie about star-crossed lovers may make you sad, but that will cause you to think more about your own close relationships and appreciate them more.”

Research has also shown that relationships are generally the major source of happiness in our lives, so it is no surprise that thinking about your loved ones would make you happier, she said.

“Tragedies bring to mind close relationships, which makes us happy.”

Source: Ohio State University

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