Exposure to light during night can lead to symptoms of depression,a new study conducted on mice has found. It was found that rodents kept in a lighted room 24 hours a day showed symptoms of depression unlike mice that had a normal light-dark cycle. A total of 24 male laboratory mice were used for the research. Half were housed in light for 16 hours a day and darkness for 8 hours,while the other half had 24 hours of light. Also,half of each group had opaque tubes in their units that let them escape the light when they chose. The other half had similar tubes that were clear and let the light in. It was observed that mice which was kept in constant light,but could escape into a dark showed less evidence of depressive symptoms than those that had 24-hour light,but only a clear tube in their housing. Laura Fonken,lead author of the study and a graduate student in psychology at Ohio State University,said: ?The ability to escape light seemed to quell the depressive effects. ?But constant light with no chance of escape increased depressive symptoms.? Co-author Randy Nelson,a professor of neuroscience and psychology at Ohio State,suggested that artificial lighting can have similar affects on humans. He said: ?The increasing rate of depressive disorders in humans corresponds with the increasing use of light at night in modern society. ?Many people are now exposed to unnatural light cycles,and that may have real consequences for our health.? The researchers presented the study in Chicago at the annual meeting of the Society for Neuroscience. It will also feature in the December issue of the journal Behavioural Brain Research.