Just about every traveler knows the immediate feeling of jet lag.
"Being tired. Not really being with it. Not a lot of energy," says Michael Dulka, a traveler from Seattle.
On the busiest travel day of the year, researchers at U.C. Berkeley revealed the findings of a new study that says just when you thought jet lag couldn't get any worse, it actually does. For the first time ever, they looked at what happens after the jet lag wears off.
"The takeaway is that if you are repeatedly jet lagged, you're in danger causing potential damage to your brain," says Associate professor of psychology Lance Kriegsfeld.
Twice a week for a month Kriegsfeld and his team subjected hamsters to time shifts equal to a New York to Paris flight. Even after the hamsters went back to their normal schedules, they had trouble learning and remembering simple tasks and they had fewer brain cells -- researchers blame the jet lag.
"That leads to a reduction in the number of neurons that are added to the adult brain and these new neurons are critical for the formation of certain types of new memories," says Kriegsfeld.
Now there is one surefire way to avoid those short term, very nagging effects of jet lag. Researchers say that is to allow one full day of recovery for every hour shift in the time zone you've endured.
Even if the long term affects of jet lag has dangerous consequences, regular travelers don't seem ready to give up their time in the air just yet -- at least, not when they've got to get home for the holidays.