Effects of light on human circadian rhythms, sleep and mood

This review explores how light influences circadian rhythms, sleep, and mood. Light exposure regulates the body’s master clock in the brain, affecting sleep timing, quality, and alertness. Morning light advances sleep schedules, while evening light delays them, impacting melatonin levels. Excessive artificial light, particularly blue light from screens, disrupts sleep and mood. However, light therapy—exposure to bright light during specific times—can improve sleep, stabilize mood, and treat disorders like depression and circadian rhythm sleep disorders. These findings underline the importance of managing light exposure for optimal brain health and cognitive performance.

To improve sleep and mood, maximize exposure to natural light in the morning and minimize artificial light, especially from screens, in the evening. Use warm, dim lighting before bedtime and consider light therapy for managing circadian rhythm disruptions or mood disorders. These practices align with strong evidence on light’s regulatory role in sleep and circadian health, though individual sensitivity may vary.