Research
Hormonal
Light is the primary circadian synchronizer in humans, capable of eliciting weak (Type 1) or strong (Type 0) resetting depending on stimulus strength and timing.
Treat light as your primary sleep regulator. Morning bright light and evening dim light are critical for setting your internal clock. Avoid bright light at night and seek bright light during the day to maintain a healthy circadian rhythm.
StrongSupportsVERY_HIGH confidence
light is now recognized as the principal circadian synchronizer in humans, capable of eliciting weak (Type 1) or strong (Type 0) resetting, depending on stimulus strength and timing.
Why this rating
Based on extensive human studies, phase-response curves, and molecular confirmation across species.
Source
Sleep and Circadian Rhythms in Humans
Charles A. Czeisler et al. · Cold Spring Harbor Symposia on Quantitative Biology · 2007
DOI 10.1101/sqb.2007.72.064
narrative_reviewCited 403×
Read the paper DOI resolved against Crossref · corpus check 2026-06-10
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