I know for a fact that you can actually feel and probably look like this double-headed monster when you are suffering from jet lag!
Yes the myths are true - it's worse if you are travelling in an eastward direction, if you are above the age of 50, if you are on your period, if you are hung over and if you are already stressed before your flight.
For those who love definitions, jet lag or desynchronosis or secondary circadian dysrhythmia is a physiological disruption of the circadian rhythm resulting in sleep disorder when travelling across a number of time zones. There are 24 time zones, so for example, flying from KL to London is equivalent to 7 time zones.
The above negatives, notwithstanding, the traveller can expect recovery time to take at least a day or more per time zone to recover. Do the math! 7 - 14 days at least.
Morning people are affected worse than night owls. Apart from insomnia, fatigue, diarrhoea, constipation, dehydration, anxiety, irritability, nausea and headache are common associated problems.
Argentinian scientists (BBC News 22 May 2007) proved that hamsters exposed to light therapy (apparently equivalent to flying eastwards - go figure?) recovered 50% faster with Viagra.
Hooray . . . if you are a hamster with spare Viagra!
In the general population, 25% are minimally affected. The 25% who can be badly affected are willing to get their hands on anything for a full nights' sleep.
How about over the counter (OTC) melatonin?? In 2005, MIT meta analysis of 17 peer reviewed studies using melatonin showed it was effective in helping people fall asleep at 0.3 mg dose. A profitable market for various alternative remedies is out there.
To help get in control of the situation, here are a few suggestions for before and after time zone travel:-
keep well hydrated, avoid alcohol and caffeine, exercise, a diet higher in protein than carbohydrates, take naps to catch up on sleep and wise use of sleep medication. Nothing new. You basically have to tough it out.
NB: Viagra is taken at your own risk . . . unless you are a hamster . . . sweet dreams!