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Be Careful, Don’t Let Your Night Light Affect Your Mood

h4jAPeR1OTbXEZypOzBSd2je0n5Ked3ebpTAHs0RV__0AQAAdwEAAEpQ_260x196In cities that are ablaze with lights, nights with flowing light and color seems to be more exciting than daytime. However, a new study published on Journal of Neuroscience suggests that different colors of the night light might make a big difference on health.

The research is directed by Randy Nelson, a professor of neuroscience and psychology at the Ohio State University. The researchers found that the hamsters exposed to red light at night showed significantly less evidence of depressive-like symptoms or changes in brain activities associated with depression, comparing with those exposed to blue and white light. It was found that blue light had the worst effects on the hamsters’ moods while the hamsters that had total darkness at night behaved most normal. These new findings might have important implications for human.

Although hamster, a nocturnal animal, which is different from human, “However, when exposed to night light, these two animals show plenty of similarities in terms of gene expression and hormone secretion.” Nelson said:” The night light would not affect hamsters’ sleeping, so we have to exclude the influence of sleep disorder.”

The researchers exposed adult female Siberian hamsters under four different nighttime light conditions with no light, dim red light, dim white light and dim blue light, among which, the condition of dim white light is found in normal light bulbs. They investigated the hamsters’ depressive symptoms via examining the hamsters’ intake amounts of sugar water—normally, hamsters enjoy drinking sugar water and if they drink sugar water less than normal, it is seen as an evidence of a mood problem.

The results demonstrated that hamsters that were kept in blue and white light drank significantly decreased amount of sugar water compared to those kept in red light. “However, their depressive symptoms could disappear after being kept in darkness for two weeks.” Said Nelson.

The researchers also discovered that compared with the hamsters exposed to red light or in total darkness, those in blue and white light showed dramatically reduced density of dendritic spines, which is linked to depression.

The researchers pointed out that such effect might be mediated by the specialized photosensitive cells in the retina, ipRGCs. These cells are most sensitive to blue wavelengths and least sensitive to red wavelengths. They not only take part in the regulation of circadian rhythms, but also deliver light information corresponding with emotions and moods to related brain areas.

The findings might have important implications for humans, particularly those who work regularly on night shifts. Nelson suggests:” night-shift workers should use strong white light and sleep in completely dark environment or some light tight places, so they can synchronize their circadian clock to the light-dark shifting.” And generally, people should choose red light instead of white light for bedroom and bathroom lighting.


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