Seasonal Rhythms — Photoperiod, Melatonin & SAD

🌅 Seasonal Rhythms

Day length changes with latitude and season via Earth's axial tilt. Shorter days trigger longer melatonin secretion windows; in susceptible individuals, light deprivation reduces serotonin and causes Seasonal Affective Disorder (SAD). Light therapy compensates by suppressing melatonin onset.

🎛 Parameters

Latitude 51°N Current month Jan Light therapy (lux·h) 0

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📊 Current stats

Day length

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Melatonin h

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Mood index

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Sunrise

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