Symptoms of jet lag
The symptoms of jet lag are different for everyone. It also depends on how far you have flown, how many time zones you have crossed and in which direction you have travelled.
READ MORE http://hcd2.bupa.co.uk/fact_sheets/html/jetlag.html
Cause
When traveling across a number of time zones, the body clock will be out of synchronisation with the destination time, as it experiences daylight and darkness contrary to the rhythms to which i READ MORE http://en.wikipedia.org/wiki/Jet_lag