Jet lag, also jetlag or jet-lag, is a physiological condition which is a consequence of alterations to the circadian rhythm. Such alterations result from daylight saving time, altered day length, or as the name implies, transmeridian travel as on a jet plane. They are known as desynchronosis, dysrhythmia, dyschrony, jet lag, or jet syndrome. The condition is generally believed to be the result of disruption of the "light/dark" cycle that entrains the body's circadian rhythm. It can be exacerbated by environmental factors.

The condition of jet lag generally lasts many days or more, and medical experts have deemed that a recovery rate of "one day per time zone" is a fair guideline. Good sleep hygiene promotes rapid recovery from jet lag.

Causes

When traveling across a number of time zones, the body clock goes out of sync with the destination time, and so it experiences daylight and darkness contrary to the rhythms to which it has grown accustomed. It is not common to get jet lag from a crossing of only one or two time zones. In jet lag, the body's natural pattern is upset, as the rhythms that dictate times for eating and sleeping no longer correspond to the environment of the destination.

Jet lag occurs because the body cannot immediately realign these rhythms. The speed at which the body readjusts itself to new daylight/darkness hours and eating/sleeping patterns is entirely dependent upon the individual. Thus, while it may take a few days for some people to readjust to a new time zone, others seem to experience little disruption to their body's natural sleeping patterns.

Symptoms

The symptoms of jet lag can be quite varied, though on the whole, an individual may experience the following:
Dehydration and loss of appetite
Headaches and/or sinus irritation
Fatigue
Disorientation and/or grogginess
Nausea and/or upset stomach
Insomnia and/or highly irregular sleep patterns
Irritability, irrationality
Mild depression