Night Light Color May Impact Your Mood: Red Versus Blue

What color is your child's night light? You may want to reconsider which one they use. It turns out that the color of a night light can affect an individual's mood, causing the person to be either more depressed or happier in the morning.

In order to test how colored lighting might affect an individual, the researchers employed hamsters. More specifically, they examined the role of specialized photosensitive cells in the retina, called ipRGCs. These cells don't have a major role in vision, but detect light and send messages to a part of the brain that helps regulate the body's circadian clock. This clock helps determine when people feel either sleepy or awake.

The scientists conducted several tests with the hamsters. In one experiment, they exposed adult female hamsters to four weeks each of nighttime conditions with no light, dim red light, dim white lights or dim blue light. They then checked for depressive-like symptoms.

So what did the researchers find? It turns out that the hamsters kept in the dark at night were the happiest. They were followed closely by those exposed to red light. The hamsters that lived with dim white or blue light, though, seemed to be the most depressed.

"Our findings suggest that if we could use red light when appropriate for night-shift workers, it may not have some of the negative effects on their health that white light does," said Randy Nelson, co-author of the new study, in a news release.

In order to confirm their findings, the researchers then examined the hippocampus region of the brains of the hamsters. It turns out that the blue light and white light hamsters had a significantly reduced density of dendritic spines compared to the other hamsters. Dendritic spines are hairlike growths on brain cells that are used to send chemical messages from one cell to another and a lowered density of them has been linked to depression.

"In nearly every measure we had, hamsters exposed to blue light were the worst off, followed by those exposed to white light," said Nelson. "While total darkness was best, red light was not nearly as bad as the other wavelengths we studied."

The findings reveal that when you're in the dark, you may want to strongly consider what type of light you plan to use. Instead of using a white light, try the red one; it could make you feel better in the morning.

The findings are published in The Journal of Neuroscience.