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Not medical advice. The Atlas is not a substitute for a clinician who can examine you.

Jet Lag

Acute Circadian Desynchrony

Evidence grade 4 of 5, Strong. Read how the Atlas grades evidence.

15 human trials, about 200 studies, >5,000 participants. The written rationale for this grade is still being prepared.

FDA
Melatonin/light evidence-based
WADA
Not prohibited

Reference only. Not medical advice.

What can go wrong

Most marketed jet-lag cures are unproven; the genuine levers (timed light, low-dose melatonin) require getting the direction and timing right, and getting them wrong can worsen the misalignment. Melatonin is a supplement, not a tightly regulated medicine in many markets, so potency can vary. The Cochrane review specifically cautioned that people with epilepsy and patients taking warfarin may come to harm from melatonin. Melatonin and light-timing decisions for children, during pregnancy, or alongside other medications should be discussed with a qualified healthcare provider before use; this entry is informational and not a treatment protocol.

Jet lag is acute desynchrony between the central clock (the SCN) and a new time zone after rapid travel across multiple zones. The clock re-entrains slowly, roughly 1 hour per day after eastward travel and about 1.5 hours per day after westward travel per the CDC, and eastward travel (requiring a phase advance) is consistently harder than westward (a phase delay) because the human intrinsic period runs slightly longer than 24 hours. The evidence-based toolkit is correctly timed bright light, correctly timed low-dose melatonin, adjusted sleep and meal timing, and limiting alcohol. Light and melatonin act in opposite directions depending on travel direction, so getting the timing right matters more than the dose. This is associated with meaningfully faster adaptation in controlled trials.

Eastward is harder than westward. The clock re-syncs about one hour per day.

What people take it for

What it is taken for. Approval, where it exists, covers only some of these.

  • Travel circadian recovery after crossing multiple time zones
  • Pre-adapting sleep and light timing before eastward trips
  • Athletic and business travel performance management
  • Reducing travel-related insomnia and daytime sleepiness

What people get wrong

  • Often saidMelatonin fixes jet lag by making you sleep

    ActuallyIt is associated with shifting the clock toward the destination, not primarily with sedation. The Cochrane review found 0.5 to 5 mg immediate-release equally effective for jet lag, and taking it at the wrong clock time can shift you the wrong way, so timing is the active ingredient.

  • Often saidEastward and westward jet lag are the same

    ActuallyEastward travel (advancing the clock) is consistently harder than westward (delaying it). The human intrinsic period is slightly longer than 24 hours (about 24.2 hours), so the CDC cites adaptation of roughly 1 hr/day eastward versus about 1.5 hr/day westward.

  • Often saidMore melatonin works better

    ActuallyThe Cochrane review found no added benefit above 5 mg, and the CDC notes high doses can linger and act at the wrong clock time. Slow-release 2 mg was relatively ineffective, suggesting a sharp, correctly timed pulse matters more than total dose.

  • Often saidJust get as much sunlight as possible at the destination

    ActuallyLight is directional. After eastward travel, indiscriminate bright light in the wrong window can be counterproductive because it pushes the clock the wrong way; the recommended approach depends on travel direction relative to the body temperature minimum (Roach and Sargent 2019).

Who profits, and who pushes back

  • Dr. Steven Lockley

    Sells this. Has a commercial interest in a product sold as this compound, as of July 2026.

    Promotes itHarvard; Timeshifter advisor

    Built evidence-based jet-lag algorithms (Timeshifter app); genuine science with a commercial product.

  • Travel and sports chronobiologists

    Promotes itAcademic

    Apply light and melatonin timing to optimize travel adaptation.

  • Andrew Herxheimer and Keith Petrie (Cochrane reviewers)

    Pushes backAuthors, Cochrane systematic review on melatonin for jet lag

    The review reports melatonin is 'remarkably effective in preventing or reducing jet-lag' yet cautions that 'people with epilepsy, and patients taking warfarin may come to harm from melatonin,' tempering enthusiasm with a safety flag.

  • Greg Roach and Charli Sargent

    Pushes backSleep and circadian researchers, Frontiers in Physiology 2019 review

    They warn that for eastward travel 'indiscriminately maximizing exposure to sunlight' can be counterproductive, because contradictory light signals inhibit the phase advance the traveler needs, so direction-specific timing matters more than sheer light.

  • AASM Standards of Practice Committee (Morgenthaler et al.)

    Pushes backAASM Practice Parameters, Sleep 2007

    The committee rates timed melatonin a Standard but timed light exposure only an Option for jet lag disorder, signaling that real-world symptom evidence for light is weaker than its well-established phase-shifting mechanism.

Where the research comes from

Share of published research by country of origin.
PlaceShare of published research
USA38%
Europe32%
Asia18%
Other12%

Research published from: Global.

How we got here

Jet lag became a named condition only with the jet age of the mid-twentieth century, when aircraft first carried travelers across many time zones faster than the body clock could follow. The underlying biology was worked out across cultures of laboratory chronobiology: researchers mapped the human phase response curve to light, measured the intrinsic circadian period at roughly 24.2 hours (Czeisler and colleagues), and demonstrated that timed melatonin could shift the clock. Field trials through the 1980s and 1990s, synthesized in the 2001 Cochrane review, established melatonin as an effective countermeasure. Sleep medicine bodies then formalized guidance: the American Academy of Sleep Medicine issued practice parameters in 2007 rating timed melatonin as a Standard for jet lag disorder. More recently, algorithmic tools translate phase response curves into personalized light, dark, melatonin, and caffeine schedules for specific itineraries.

  1. 1950s-1960sJet lag recognized as a condition of the jet age as commercial aircraft outpace the body clock
  2. 1980s-1990sField and laboratory trials show timed light and melatonin can deliberately shift the human clock
  3. 2000Czeisler and colleagues report the human intrinsic circadian period at about 24.2 hours (PNAS), grounding the eastward-versus-westward asymmetry
  4. 2001Cochrane review (Herxheimer and Petrie) pools 10 randomized trials and finds melatonin effective for jet lag
  5. 2007AASM Practice Parameters (Morgenthaler et al., Sleep) rate timed melatonin for jet lag disorder as a Standard
  6. 2018Timeshifter releases a phase-response-curve-based jet-lag app developed with Harvard's Steven Lockley

At a glance

Re-sync rate
~1 hour/day
Eastward
Harder (phase advance)
Best tools
Light + low-dose melatonin
App
Timeshifter (Lockley)

What this entry does not yet cover

What follows is unfinished work on our side, not a finding about Jet Lag. A short entry is not a safe entry.

  • Cost and market. We have not documented what it sells for or who sells it.
  • Supply chain. We have not mapped where it is made.
  • Who uses it. We have not documented the user groups.
  • What could change. No forward-looking summary yet.
  • How it compares. We have not set it against the alternatives.
  • Children and teenagers. We have not checked what is known about younger people.

Sources