Scientists have said that the use of laptop at night, especially the light that emits from it can fuel depression.
A study of mice that were exposed to a cycle of 3.5 hours of light and 3.5 hours of darkness showed that it caused them to develop depression like symptoms. They were found to have increased levels of stress hormone, cortisol.
Shift workers working at night could be prone to risks of depression, as bright light in the early hours can increase levels of stress hormone which can also inhibit the ability to learn.
It might be a good idea to keep fewer lamps switched on at night while working.