Why is bright light at night bad for sleep?

Bright light at night is detrimental to sleep for several reasons. Here are the key points discussed by Andrew Huberman and other experts on the Huberman Lab:

1. Melatonin Suppression: Melatonin, a hormone naturally released in the evening, makes you feel sleepy. Exposure to bright light, especially between 10:00 p.m. and 4:00 a.m., can inhibit melatonin production, making it harder to fall and stay asleep 1.

2. Circadian Rhythm Disruption: Seeing bright light late in the evening can shift your circadian clock. The eyes' sensitivity to light increases at night, making it easier for even low levels of light to reset your internal clock, disrupting sleep patterns 2.

3. Dopamine Reduction: Bright light exposure in the middle of the night can suppress dopamine, a neuromodulator important for mood and motivation. This suppression can lead to lower mood and increased depression risk 3 4.

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     1

     Optimize Your Sleep

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     2

     Light and Circadian Rhythm

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     3

     Light and Sleep

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     4

     Light and Mood

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     5

     Light and Hormones

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     6

     Sleep and Myopia

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4. Impact on Hormones: Light exposure at night can also affect hormone levels, including reducing testosterone and estrogen due to suppressed dopamine release 5.

5. Myopia Risk in Children: Sleeping with nightlights or dim lights can increase the risk of myopia (nearsightedness) in children. This is due to light penetrating through thin eyelids, affecting the retina 6.

In summary, avoiding bright light, particularly from overhead sources, between 10:00 p.m. and 4:00 a.m., and ensuring a dark sleeping environment can help maintain healthy sleep patterns and overall well-being 1.