Melatonin

Story

Connected to · 5

antagonism · 1

Caffeine + L-Theanine
Caffeine and melatonin start out on two separate lines: caffeine blocks the adenosine line of sleep pressure, while melatonin is the body clock's signal that night has come. But evening caffeine also moves the clock itself later: in Burke 2015, caffeine equal to a double espresso taken 3 hours before bed delayed the melatonin rhythm by about 40 minutes, nearly half the delay from 3 hours of bright evening light. So a late-afternoon coffee plus a bedtime melatonin tablet has the first pushing back the very clock the second is meant to set.

regulates · 3

Insomnia
The body clock is one of the three main threads of insomnia: darkness triggers melatonin release, and morning light resets the clock. So melatonin here is a timing signal, not a sleeping pill; in one meta-analysis it shortened the time to fall asleep by only about 4 minutes. What matters is when you take it, not how much.
Shift Work · Circadian
The core problem with shift work is not less sleep but an internal clock out of step with the light and dark outside: the body's master clock (the suprachiasmatic nucleus) is set by light, and melatonin is the darkness signal it sends. The International Agency for Research on Cancer (IARC) classifies night shift work as Group 2A, probably carcinogenic; the grade describes how certain the evidence is, not how large the harm is.
All-Nighter
Screen light before bed suppresses the evening rise in melatonin and pushes back the time you start to feel sleepy. So staying up late is not only a matter of willpower; part of it is light delaying your body clock.

contrast · 1

Glycine
They sit on the same sleep-aid shelf but act in different places: melatonin tells the body clock that night has come and helps most with rhythm problems (Zhdanova 2001 found a small dose effective in insomniacs over 50); glycine improved subjective sleep in small trials, possibly by widening peripheral blood vessels and lowering core temperature (Yamadera 2007). Whether taking both adds anything has not been tested; for chronic insomnia, CBT-I is still the first-line treatment.

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Stop 1/6

How the body makes it at night

EVIDENCEGUIDE 1 · REVIEW 3 · RCT 1

READ THE ORIGINAL

Melatonin is not a sleeping pill that knocks you out. It is a message: it is dark now, time to get ready for sleep. About two hours before your usual bedtime, a pea-sized gland deep in the brain, the pineal gland, starts releasing it into the blood.

How does it know it is dark? Through a small group of cells in the eye that do nothing but measure brightness: intrinsically photosensitive retinal ganglion cells (ipRGCs). They carry a light-sensitive pigment called melanopsin that responds most to blue light around 480 nm, and they report light and dark straight to the brain's master clock, the suprachiasmatic nucleus (). While there is light, the SCN holds melatonin down; once it is dark, the SCN lets go and melatonin climbs. Staring at a bright screen at night tells the SCN it is still daytime.

So taking melatonin mainly changes when you start to feel sleepy; its direct sleep-inducing effect is small. It suits situations where the body clock is out of step, such as jet lag. If you have young children, store it like a medicine, gummies above all: if a child who swallowed some is too drowsy to wake or is breathing abnormally, call emergency services now.

Educational content, not medical advice — consult a clinician.

Back

Melatonin

Story

Connected to · 5

antagonism · 1

Caffeine + L-Theanine
Caffeine and melatonin start out on two separate lines: caffeine blocks the adenosine line of sleep pressure, while melatonin is the body clock's signal that night has come. But evening caffeine also moves the clock itself later: in Burke 2015, caffeine equal to a double espresso taken 3 hours before bed delayed the melatonin rhythm by about 40 minutes, nearly half the delay from 3 hours of bright evening light. So a late-afternoon coffee plus a bedtime melatonin tablet has the first pushing back the very clock the second is meant to set.

regulates · 3

Insomnia
The body clock is one of the three main threads of insomnia: darkness triggers melatonin release, and morning light resets the clock. So melatonin here is a timing signal, not a sleeping pill; in one meta-analysis it shortened the time to fall asleep by only about 4 minutes. What matters is when you take it, not how much.
Shift Work · Circadian
The core problem with shift work is not less sleep but an internal clock out of step with the light and dark outside: the body's master clock (the suprachiasmatic nucleus) is set by light, and melatonin is the darkness signal it sends. The International Agency for Research on Cancer (IARC) classifies night shift work as Group 2A, probably carcinogenic; the grade describes how certain the evidence is, not how large the harm is.
All-Nighter
Screen light before bed suppresses the evening rise in melatonin and pushes back the time you start to feel sleepy. So staying up late is not only a matter of willpower; part of it is light delaying your body clock.

contrast · 1

Glycine
They sit on the same sleep-aid shelf but act in different places: melatonin tells the body clock that night has come and helps most with rhythm problems (Zhdanova 2001 found a small dose effective in insomniacs over 50); glycine improved subjective sleep in small trials, possibly by widening peripheral blood vessels and lowering core temperature (Yamadera 2007). Whether taking both adds anything has not been tested; for chronic insomnia, CBT-I is still the first-line treatment.

Read full story

Stop 1/6

How the body makes it at night

EVIDENCEGUIDE 1 · REVIEW 3 · RCT 1

READ THE ORIGINAL

Melatonin is not a sleeping pill that knocks you out. It is a message: it is dark now, time to get ready for sleep. About two hours before your usual bedtime, a pea-sized gland deep in the brain, the pineal gland, starts releasing it into the blood.

How does it know it is dark? Through a small group of cells in the eye that do nothing but measure brightness: intrinsically photosensitive retinal ganglion cells (ipRGCs). They carry a light-sensitive pigment called melanopsin that responds most to blue light around 480 nm, and they report light and dark straight to the brain's master clock, the suprachiasmatic nucleus (). While there is light, the SCN holds melatonin down; once it is dark, the SCN lets go and melatonin climbs. Staring at a bright screen at night tells the SCN it is still daytime.

So taking melatonin mainly changes when you start to feel sleepy; its direct sleep-inducing effect is small. It suits situations where the body clock is out of step, such as jet lag. If you have young children, store it like a medicine, gummies above all: if a child who swallowed some is too drowsy to wake or is breathing abnormally, call emergency services now.

Educational content, not medical advice — consult a clinician.