I always bring black plastic sheets with me when going North in the Summer to make my bedroom pitch dark, but the local people seem to not be bothered by the Sun at night. However, they do say that they need less sleep, some say that they often can't sleep, get up at 2 am and start their work without being affected by sleep deprivation. Here we can read:
The locals sleep well, as they’ve had a long period to get used to the long hours of daylight as the spring progresses. We do however sleep less, because the light makes us energetic and lively, and elevates our mood, so the body needs less sleep.
I don't understand how this can work on the long term, it seems to me that a prolonged period of sleeping less will drain your energy levels.