This article talks more about genetics rather than light, so I'm not sure where you're coming from here. They also cover the fact that there are multiple proce

This article talks more about genetics rather than light, so I'm not sure where you're coming from here. They also cover the fact that there are multiple processes that affect the onset of sleep, and daylight is just one of them. It's also possible that Scandinavians have some genetic differences that reduce the effect of long days on their ability to fall asleep.