There is a light pollution movement that says lighting at night obstructs melato

Question

There is a light pollution movement that says lighting at night obstructs melatonin production. They say:

What makes you fall asleep are changes in the level of the hormone melatonin circulating in your body. During the day, light stimulates a part of the brain. This brain part (known as the suprachiasmatic nucleus) tells the pineal gland to decrease the melatonin level when it is light out and to increase it when it is dark. The brighter the light, the bigger the decrease and the darker the dark, the bigger the increase of melatonin. By making your days lighter and your nights darker, you can improve both the quality of your sleep and the amount of time it takes you to fall asleep.

and recommend all kind of protection against the light,

Dark Nights: Make your nights as dark as possible. Draw the curtains, close the shades and keep the lights off. Try a sleep mask if you can

Explanation / Answer

The release of the hormone melatonin is responsible for the feeling of sleepiness. It is released by the pineal gland and production starts when the light fades, as it's production is inhibited by light stimulation of the retina, the onset of the production is called dim-light melatonin onset.

Read more about this at this previous answer.

This study on blind people will show you that the light entering the eyes is the (main at least) regulator of melatonin rhythms. They took blind people, 19 of whom could perceive light and 30 who could not, and showed that 14 of 19 light perceivers had normal melatonin rhythms while 23 of the light-blind people had abnormal or unclassifiable rhythms.

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