Jet lag is a condition in which a person's normal sleep cycle is disturbed by travel across time zones.

What is going on in the body?

A person who travels between different time zones need time for his or her internal body clock to reset itself and adjust to the new time zone. The body usually develops a set pattern of times when it is used to eating, sleeping, working, and performing other activities. Jet lag occurs because the body is reacting to a change in the schedule of normal activities.

What are the causes and risks of the condition?

The primary cause of jet lag is crossing time zones and then trying to get the body to react and adjust right away. Flying north or south does not cause jet lag. The more time zones crossed, the more difficult it is for the body to adjust to the new time zone. The body can generally adjust to a time change of about 1 or 2 hours per day. After travel across three time zones, which often occurs in a trip from the west to the east coast, the body may need up to 3 days to adjust to the new time.