Late-Night Light May Trigger Depression

Can too much light at night affect your mood? Scientists have wondered if exposure to artificial light may be associated with the observed increasing rates of depression. Recent research published in Molecular Psychiatry on female hamsters suggests that exposure to artificial light at night may, in fact, trigger depression.

The investigation was led by Tracy Bedrosian, a Ph.D. candidate in neuroscience at The Ohio State University. She evaluated whether chronic exposure to low levels of artificial light at night may contribute to depression-like behaviors in the hamsters. Apparently the hamsters became less interested in sugar water when they were feeling down in the dumps. (Incidentally, she chose to evaluate female hamsters due to the higher rate of depression in women.)

As part of the study, the hamsters were exposed to low levels of light at night. In fact, the light exposure was only 5 lux. For comparison, a family living room light is reported to have a brightness of 50 lux. Light has a key role in affecting the circadian rhythm and release of melatonin.

The researchers subsequently analyzed the brains of the hamsters for the effects on the hippocampus, an area of the brain that is responsible for memory. They also evaluated markers of inflammation that can be elevated in depression. The research demonstrated a reversible increase in a marker called tumor necrosis factor in the hippocampus which may be correlated with increased depression.

Certainly hamsters are not people and further research needs to occur to demonstrate the same association exists in humans. However, sleep and depression seem to walk hand in hand and difficulties sleeping, especially insomnia, are strongly linked to mood problems.

There are many reasons to reduce your light exposure at night, and avoiding depression may just be another.

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