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Depression linked to late night screen use

24th July 2012

Recent research from the United States shows that late-night exposure to light from a television or computer screen could be a risk factor for depression.

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According to a team of neuroscientists at Ohio State University Medical Center, sitting in front of a screen just before bed, or leaving it on when you fall asleep could boost your chances of becoming depressed.

Late-night exposure to artificial light has already been identified as a risk factor for breast cancer and obesity, but little is yet known about its link with mood disorders like depression.

For the purposes of the study, which was partly funded by the U.S. Department of Defense, the researchers exposed hamsters to dim light at night.

They then recorded behavioural changes and differences in brain chemistry that are linked to depression in humans.

The link could be a factor in surging depression rates during the past 50 years, which have coincided with a rise in people's exposure to artificial light late at night.

According to lead author Tracy Bedrosian, the links were particularly pronounced in women, who are twice as likely to become depressed as men.

She said that the team's results from the study in hamsters were consistent with what is already known about depression in humans.

Writing in the journal Molecular Psychiatry, Bedrosian's team described an experiment in which hamsters were exposed to dim light at night equivalent to a television screen in a darkened room for a period of four weeks.

A control group was exposed to a typical day-night light cycle.

The experimental group was observed to be less active and showed much less interest than usual in drinking sugar water, symptoms with mimic those of depression in humans.

The hamsters exposed to late-night light also showed marked changes in their hippocampus, a part of the brain affected in humans with depression.

They also produced more of a chemical messenger that is mobilized when the body is injured or infected -- a protein known as tumor necrosis factor (TNF).  a

According to study co-author Randy Nelson, TNF causes inflammation in its attempts to repair damage to the body, which makes the relationship between dim light at night and increased TNF production particularly meaningful.

He said that previous studies have found a strong association in people between chronic inflammation and depression.

While blocking the TNF with a drug dampened its production, the other effects remained.

However, the symptoms were found to be reversible, because when the experimental group of hamsters was returned to a normal light-dark cycle, their brains returned to normal within about two weeks.

Bedrosian said that people who stay up late in front of the television and computer could potentially reverse the damage by minimising their exposure to artificial light at night.

 

 

 

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