Jet lag is caused by rapid eastward or westward travel across multiple timezones, resulting in a circadian misalignment, or a mismatch between internal biological time and environmental time.
Symptoms include daytime fatigue and sleepiness, as well as insomnia in the new time zone, and may be exacerbated by disturbed or shortened sleep duration before and during travel.
The circadian principles used in the management of jet lag are similar to those used in the management of shift work. However, as environmental cues often support adaptation to a different time zone after travel, jet lag symptoms will typically subside in a few days.
In some cases the symptoms can last for weeks, and it may be helpful to see your sleep physician if the disorder is affecting your ability to function normally.