Jet Lag Disorder
Reviewed by our editorial team
Last updated: 2026-04-01
Jet lag, also known as desynchronosis or jet lag disorder, is a temporary circadian rhythm sleep disorder that occurs when you travel quickly across multiple time zones. Your internal body clock (circadian rhythm) remains synchronized with your original time zone, while the environment in your new destination is on a different schedule.
This mismatch leads to symptoms such as daytime fatigue, nighttime insomnia, digestive issues, and a general feeling of being 'unwell.' While it is a temporary condition, for frequent travelers, it can lead to chronic sleep issues and decreased cognitive performance during important business or social trips.
The Direction Matters: East vs. West
Traveling east is generally harder on the body than traveling west. When you fly east, you 'lose' time, and your body must try to fall asleep earlier than its internal clock expects. This is difficult because the circadian rhythm is easier to 'stretch' (lengthen) than to 'shrink' (shorten).
When traveling west, you 'gain' time, and your body must stay awake longer. For most people, pushing through tiredness to stay awake is easier than trying to force sleep when the brain is still in 'daytime mode.' As a rule of thumb, it takes about one day per time zone crossed to fully adjust when traveling east.
Common Symptoms of Desynchronosis
The most prominent symptom is sleep disruption: you may feel wide awake at 3 a.m. in London because your body thinks it is 10 p.m. in New York. During the day, you may experience 'foggy' thinking, irritability, and decreased physical coordination.
Gastrointestinal issues are also very common, including indigestion, constipation, or diarrhea. This is because your 'gut clock' is also out of sync, meaning your stomach expects food at times when you aren't eating, and vice versa.
The Role of Sunlight in Resetting
Sunlight is the most powerful tool for resetting your internal clock. By exposing yourself to bright outdoor light at specific times in your destination, you can signal your brain to shift its rhythm. If you traveled east, you need morning light. If you traveled west, you need late afternoon and evening light.
Conversely, you should avoid light at times when your body needs to be 'drifting' toward sleep. Wearing sunglasses or staying indoors during these windows can help prevent your clock from being pushed in the wrong direction.
Strategic Use of Melatonin
Melatonin supplements can be very effective for jet lag when used correctly. Taking a small dose (0.5mg to 3mg) at the desired bedtime in your new destination can help 'anchor' the new sleep time. It acts as a chemical signal to the brain that the night has begun.
It is important to time the dose correctly. If taken at the wrong time, melatonin can actually make jet lag worse by shifting your rhythm in the wrong direction. Most experts recommend starting the supplement on the first night of arrival at the destination's local bedtime.
When to Speak With a Doctor
Most jet lag resolves within a few days. However, if you are a frequent traveler and find that jet lag is causing chronic insomnia or health issues, a sleep specialist can provide a tailored light-therapy plan.
Frequently Asked Questions
References
- [1]Mayo Clinic. Jet Lag Disorder.
- [2]National Sleep Foundation. How to Prevent Jet Lag.
- [3]CDC Yellow Book. Jet Lag Information for Travelers.
The information on this page is for educational purposes only and is not a substitute for professional medical advice. Always consult a qualified healthcare provider for diagnosis and treatment.