Posted 24.07.2012 09:00:13 UTC
Updated 24.07.2012 09:00:13 UTC
The study, by a team of neuroscientists at Ohio State University Medical Center partly funded by the U.S. Department of Defense, will give screen-addicted night owls pause for thought.
The researchers - who exposed hamsters to dim light at night and picked up changes in behaviour and the brain that bore striking similarities to symptoms in depressed people - said 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.
"The results we found in hamsters are consistent with what we know about depression in humans," said Tracy Bedrosian, who led the study, published in the journal Molecular Psychiatry.
Although exposure to night-time light has been linked to an increased risk of breast cancer and obesity, the relationship with mood disorders is poorly understood.
The hamsters involved in the experiment were exposed for four weeks to dim light at night - equivalent to a television screen in a darkened room - and the results compared to a control group exposed to a normal light-dark cycle.
The experimental group was then moved back onto a normal
cycle for one, two or four weeks before they were tested.
The results showed they were less active and had a lower
than usual interest in drinking sugar water - both symptoms are
comparable to signs of depression in people.