Well, the biological rhythm can be impacted by much more than just late-night activities. I'm not talking about short term things like jet lag. I'm thinking mor

Well, the biological rhythm can be impacted by much more than just late-night activities. I'm not talking about short term things like jet lag. I'm thinking more chronic things like insomnia, chronic illness/malnutrition, emotional trauma, etc all come to mind. So it would be unfair to place all the blame on students playing WoW or partying instead of studying, for example.