Exposure to artificial light at night has been found to induce depressive-like behaviour in mice, a new study has found. The findings could help with the understanding of how exposure to excessive light at night-time triggers depression in humans. Researchers from the University of Science and Technology in China exposed mice to two hours of blue light – the same light emitted from light pollution or electronic devices like smartphones – for several weeks. They observed that after three weeks the animals displayed depressive tendencies, measured by reduced escape behaviour and decreased preference for sugar. These bouts of depression lasted up for an additional three weeks after the mice were no longer exposed to light at night.