Read up a bit on light and the mind. Blue light stimulates the brain and isn't helpful for sleep. Green is often soothing. All sorts of things.

If you think of Nordic countries or people at work in the arctic areas, many months of the year it never gets fully dark. In Iceland when I was there, at 2 am I could see details on mountains miles away. Wasn't daylight but not night either. They have blackout curtains. Physicians often do too because your circadian rhythms get out of whack and the results can lead to psychiatric disturbance.

Light therapy helps in the other end of the spectrum when it's dark in places for many months. We need light but a certain kind. Fluorescent isn't helpful at all. That's where the boxes come in.

We're not that different from plants and animals on the lower order of development.

Look for information on S.A.D lights. There are places in the north that only have sun in the summer, in the winter the sun doesn't come up. S.A.D lights give you similar effects as the sun. You should be able to find information on the Internet.