This is from the i paper
There seem to be a lot of people having sleep problems at the moment, and alive ranges from avoiding coffee to various relaxing techniques, but use of electronic devices are also involved, but the situation may not be so simple:
If you’ve wondered just why looking at your smartphone or tablet late at night makes it difficult to sleep, the answer might be in the blue light.
Researchers at Oxford university have found that different coloured light can promote or delay sleep. The team. led by Dr Stewart Peirson, were aiming to discover why exposing mice to bright light during the night caused them to both fall a sleep, and produce increased levels of a hormone linked to arousal – two physically incompatible responses. “We wanted to understand how these two effects were linked to a blue light-sensitive pigment [in the eye] called melanopsin, known to play a key role in setting out body clock.” he said.
The team exposed mice to 3 different colours of light – violet, blue and green. Green light was found to produce rapid sleep onset but blue and violet light delayed slumber. However, when the experiment was conducted on mids without melanopsin the results were reversed.