Streetlight at night Columbus - UPI Chronic exposure to artificial light at night may play some role in the rising rates of depression in humans during the past 50 years, U.S. researchers say. Lead author Tracy Bedrosian, doctoral student in neuroscience and colleagues at Ohio State University, said hamsters exposed to light at night for four weeks showed evidence of depressive symptoms, but those symptoms essentially disappeared after about two weeks after exposure to normal lighting conditions. Even changes in the brain that occurred after hamsters lived with chronic light at night reversed themselves after the hamsters returned to a more normal light cycle, Bedrosian said. "The good news is that people who stay up late in front of the television and computer may be able to undo some of the harmful effects just by going back to a regular light-dark cycle and minimizing their exposure to artificial light at night," Bedrosian said in a statement. "That's what the results we found in hamsters would suggest."