Nightlight Can Cause Mild Depression

You now have a valid reason to switch off.  A new study suggests nightlight and other light emitting objects such as computer screens, televisions, ipads can cause mild depression. 

The new study showed, 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 study from Ohio State University Medical Center found that hamsters that are 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,"

The study was published online in the journal Molecular Psychiatry.

"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."

In the new study, Bedrosian and colleagues placed a group of hamsters in an environment that provided 16 hours of normal daylight, and eight hours of dim light, equivalent to that of a television playing in a dark room. Their behavior was compared to that of a group of hamsters that spent 16 hours in daylight and eight hours in total darkness.

Hamsters exposed to dim light at night were less active each day, and were less mobile when placed in water compared to those that spent their nights in total darkness.

The study showed the presence of a particular protein found in the brain of hamsters and humans that may play a key role in how light at night leads to depression. And they found that blocking effects of that protein called tumor necrosis factor (TNF), prevented the development of depressive-like symptoms in hamsters even when they were exposed to light at night.