Shift work and jet lag are circadian timing problems; light, sleep timing and melatonin require direction and timing, not just dose.

Sleep & Circadian - Schedules & timing

Shift work and jet lag

Last reviewed 3 August 2026. How we write this.

Shift work and jet lag are circadian timing problems; light, sleep timing and melatonin require direction and timing, not just dose.

Light at one biological time can shift the clock earlier and at another can shift it later. Generic advice to seek bright light can therefore be wrong for the desired direction.

Safety-sensitive workers should address severe sleepiness with occupational or clinical support.

Educational content only. This does not diagnose, treat or replace individual advice from an appropriately qualified clinician.

Related in this classroom

How much sleep do adults need? (8 min read)
Melatonin: timing, evidence and safety (8 min read)
Chronic insomnia and CBT-I (10 min read)

Sources for this classroom

Educational content only. Not medical advice, diagnosis or treatment. Always consult a qualified healthcare professional before changing your health regimen.