I'm with Loren on this one. Everything I've heard about hangovers suggests that it's mostly due to dehydration. Tod ("Commori") even talks about "hockey hangovers", the day after he plays hockey, having the same symptoms as a hangover because he's unable to keep himself hydrated enough on those nights. I also notice that if I didn't drink enough fluids on any given day, I will wake up with a headache the following morning.