The colour of your night light may make a big difference to your mood, research conducted on hamsters suggests.
The study found that hamsters exposed to blue or white light at night had more depressive-like symptoms and depression-related changes in the brain than those that were exposed to red light.
The only hamsters that did better than those exposed to red light were those that had total darkness at night, according to the study in the August 7 issue of the Journal of Neuroscience.
Although results obtained in animal studies are not always replicated in humans, the results may prove important for people, particularly those whose work night shift, which makes them susceptible to mood disorders, said study co-author Randy Nelson, a professor of neuroscience and psychology at Ohio State University.
"Our findings suggest that if we could use red light when appropriate for night-shift workers, it may avoid some of the negative effects on their health that white light does," Nelson said in a university news release.
"In nearly every measure we had, hamsters exposed to blue light were the worst off, followed by those exposed to white light," Nelson added. "While total darkness was best, red light was not nearly as bad as the other wavelengths we studied."
In addition to shift workers, others may benefit from limiting their light at night from computers, televisions and other electronic devices, the researchers pointed out. And, if light is needed, the colour may matter.
"If you need a night light in the bathroom or bedroom, it may be better to have one that gives off red light rather than white light," study co-author Tracy Bedrosian, a former graduate student at Ohio State who is now a postdoctoral researcher at the Salk Institute, said in the news release.
"Light at night may result in parts of the brain regulating mood receiving signals during times of the day when they shouldn't," Bedrosian suggested. "This may be why light at night seems to be linked to depression in some people."
The US National Institutes of Health has more about mood disorders.