A recent study at Johns Hopkins University found that being exposed to bright lights for an extended period of time causes higher levels of cortisol, the stress hormone, which can eventually lead to brain functioning problems and even depression. The study was conducted on mice, which are similar to humans in that both humans and mice have light-activated cells in their eyes which have been shown to have an effect on brain regions associated with mood and memory. One of the researchers also noted that previous studies have been done on humans that has proved light affects the limbic system of the human brain.
Read the full article here: Light at Night May Lead to Depression, Brain Functioning Problems