The possible relationship between artificial light and depression is popping up more and more frequently.
A new study done at the Ohio State University Medical Center exposed hamsters to dim light at night and picked up changes in behavior and the brain that bore striking similarities to symptoms in depressed people (h/t Medscape). The hamsters were less active and had a lower interest in drinking sugar water. There were also changes in the hippocampus that were characteristic of depression. If these results can be generalized to humans, this could mean that sitting in front of a computer or TV screen late into the night, or falling asleep with it on, could increase the risk of depression.
Other studies have suggested a link between exposure to nighttime light and increased risk of breast cancer, obesity, and increased production of tumor necrosis factor (TNF), an inflammatory marker. The latter discovery supports a previous finding of a strong association in people between chronic inflammation and depression. In addition, since electronic device screens produce fatigue-fighting blue light, chronic nighttime exposure to them may interfere with sleep. That, in turn, is a significant risk factor in depression.
The Ohio State study, which was published online in Molecular Psychiatry on July 24, also noted that a surge in exposure to artificial light at night in the last 50 years had coincided with rising rates of depression, particularly among women, who are twice as prone as men. More frequent reporting of psychiatric disorders as well as changing diagnostic criteria may, however, account for at least part of this increase.
Overall symptoms of depression were reversed once the hamsters in the Ohio State study were returned to a normal light-dark cycle. This indicates that managing exposure to nighttime light can limit its depressive effects.