bio

Melatonin

A hormone secreted by the pineal gland at night and suppressed by light, so its concentration is a chemical report on how dark it currently is. It is routinely called "the sleep hormone," and that is close enough to be misleading: melatonin is a *darkness signal*, not a sedative. It does not induce sleep so much as tell the rest of the body what the clock believes the time to be. The consequence worth noting is that the threshold for suppressing it is far lower than most people assume - roughly twilight levels, single-digit to low-tens of lux, is enough to interfere with the body's account of when night is.