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Morning Light Therapy

Morning bright light—outdoor daylight or ~10,000 lux boxes—advances circadian phase, lifts daytime alertness, and improves self-reported sleep quality; duration scales with weather and device.

Circadian effects

  • Phase advance commonly cited in the 36–45 min range with sufficient morning photopic dose
  • RCT context: 30 min ≈ 10,000 lux improved subjective alertness and shortened sleep-onset latency by ~25 min in at least one recent trial

Cortisol rhythm

  • Morning light can increase cortisol awakening response amplitude and shift the peak earlier
  • Evening cortisol may run lower when the morning anchor is strong

Delivery formats (same protocol class)

  • Light box: ~30 min at ~10,000 lux within 2 h of wake
  • Outdoor light: often 5–30 min depending on cloud cover and latitude—very bright days may need less time than heavy overcast

Related entries

  • Circadian-timed light — adds evening dim-light / spectral hygiene framing
  • Daily sunlight — vitamin D and broader daytime outdoor guidance

Tertiary map

Wikipedia: Light therapy (wikipedia-light-therapy-overview) outlines bright-light treatment history and common lux conventions; Wikipedia: Melatonin (wikipedia-melatonin-overview) frames suppression vs phase biology—both are navigation layers alongside wikipedia-circadian-rhythm-overview.

Evidence