Traveling soon? If you’re making your way east, heads up — it causes a rougher type of jetlag than if you’re heading west. It has to do with our natural circadian rhythms, which are regulated by pacemaker brain cells in our hypothalamus.

“You can think of those pacemaker cells as tiny clocks. Each, on its own, runs with a unique and different period that is slightly longer than 24 hours,” Zhixin Lu, a graduate research assistant and study author, told LifeZette.

Our natural circadian rhythms, as it turns out, give us about 24.5 hours a day.

They normally operate in a regular pattern that’s controlled by our exposure to light. When that’s interrupted or thrown off, the cells cannot adjust instantly — and you wind up with a nasty case of jetlag.

Our natural circadian rhythms give us about 24.5 hours a day. Not everyone has an internal clock like that — some of us run on less than 24 hours a day.

That 30 minutes explains the rather large east-west asymmetry for jetlag recovery. In other words, it makes it easier to travel in a direction that lengthens the day — west — than to travel in a direction that shortens the day — east.

Researchers used a math model to simulate what happens to brain cells during travel. The model, in essence, explores what would happen to an individual if he or she were suddenly taken from one time zone and dropped in another.

Related: 10 Ways to Stop Sabotaging Your Vacation

The findings went along with a conventional notion that it’s worse on us when we travel east. It would take a person a little less than four days to recover from a trip in which he passed westward through three time zones; six time zones takes about six days; and nine time zones takes roughly eight days.

“Individuals [flying east] should get as much exposure to sunlight as possible after arrival,” said one researcher.

For those traveling east, however, recovery takes longer. If you’re going through three time zones, it takes more than four days; six time zones takes about eight days; and nine time zones eats up 12 days.

“Individuals should get as much exposure to sunlight as possible after arrival. Also, our model shows that, counterintuitively, flying across nine time zones eastward instead of 12 time zones is the type of travel where jetlag is the toughest to overcome,” Lu added.

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Then There’s Social Jetlag
Flying isn’t the only way to experience jetlag, however. Our daily schedules can cause something known as social jetlag. The term means offsetting our circadian clocks when daily schedules don’t meet the natural rhythms of our bodies. It can be especially hard on people who work different shifts, but it can occur in those who, for example, have to wake up extremely early when their bodies would rather be sleeping.

[lz_bulleted_list title=”Jet Lag Symptoms” source=””]Insomnia or excessive sleepiness|Daytime fatigue|Difficulty concentrating or functioning at usual level|Constipation or diarrhea|General feeling of not being well|Mood changes[/lz_bulleted_list]

A study in Current Biology found that workers’ general well-being could be improved if work schedules took everyone’s biological clocks into account — natural early risers could work earlier shifts, while night owls could work later shifts. Researchers found a new schedule improved the well-being of workers as well as satisfaction with leisure time.

Regardless of schedules, getting enough sleep is key. Not sleeping enough has been linked to diabetes and heart disease.

If there’s not enough time to catch up on sleep, a small study last year out of Canada tested a new jetlag pill, which works to trick the body’s circadian rhythm into thinking day is night and night is day. It alters white blood cells and has a steroid-based compound, glucocorticoid, which can change the biological clock within the cells. 

Another treatment involves exposure to short flashes of light at night during sleep, which are more effective than continuous light as therapy. Researchers from Stanford University said the brief light exposure could help people better adjust to time changes.

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