A new study suggests that exposure to bright lights in the evening hours may increase the risk of depression and learning difficulties.
According to researchers at The Johns Hopkins University in Baltimore, steady exposure to bright lights at night produced signs of depression and learning disabilities in a group of laboratory mice.
It is well known that day and night rhythms can affect human metabolism, including psychological functions. Biologist Samer Hattar says this is a condition known as seasonal affective disorder, or SAD, where some people become depressed during the winter season when days grow shorter in the north. SAD is often treated successfully by having patients spend time in front of special lamps called light boxes, whose full spectrum bulbs simulate natural daylight.
Hattar’s team also believes depression and learning deficits can set in for so-called “night owls” — people who stay up very late and — because they tend to sleep in late — do not see much morning light.
That is a reaction the researchers saw in their study of mice exposed to a cycle of three-and-a-half hours of light followed by three-and-a-half hours of darkness. Hattar says the cycle did not deprive the mice of sleep, just altered their wake-sleep cycle.