It royally screws up your sleep patterns. Take me for example, I should be asleep right now. Every other soul in the house is asleep and instead I sit in a closet (my uncle put the computer in the CLOSET of all places whilst I was gone, one would think he didn't think it all that important or something) on the forums. I am so tired. I had to do things this afternoon, and now it feels like I'm just waking up, but I know I'm not. My body is waaaay out of joint right now I believe.