Recent research on jetlag

Published in Science 28 April 2000, Vol 288
(www.sciencemag.org)

Not Just Mental Symptoms
Researchers found evidence of major time shifts, ie a long flight or doing night shift work saw mesaureable changes to liver, lung and skeletal muscles. This is the first scientific evidence that suggests jetlag and shiftlag are not just "in your mind" or mental symptoms.

Six days to reajust
In the experiment those tissues measured took six days to resume their normal relationships to each other. The experiment imitataed the same size phase shift as found in either a trans-Atlantic flight or working a night shift.

This is the mechanism for jetlag and shiftlag
Because these disruptions of phase relationships are so large and sudden, unlike the changing day length, they are thought to have deleterious consequences and are likely to be the explanation of the thousands who suffer from jetlag daily and the more than 20% of the US workforce who suffer from shiftlag.