[WalterSear]

They don't. They might reduce eyestrain (I have it installed on all my computers, fwiw), but they aren't effective enough on their own to help with sleep.

In psychology grad school, I learned that a single blue photon hitting the back of the is sufficient to cause a measurable shift in melatonin output. Note: measurable is not the same as deleterious, but flux doesn't even eliminate all the blue light your computer is putting out, let alone the other sources in your house.

The only solution, baring blacking out all your windows, or removing all modern light sources from your house, or replacing them all with red lights, is 0.3-0.5 mg of melatonin a few hours before bed. Note: it's sold in the stores in 5 mg tablets - an order of magnitude too much.

http://www.gwern.net/Melatonin

[herf]

Author of f.lux here: you may want to do some more reading.

Most of the range of "alerting" light for humans is between 11-14 log photons/sec/cm^2, so one photon is sort of an enormously huge understatement.

For sleeping, it is good to be in a dark room, but for winding down, you won't mess yourself up with dim light.

Also, I think it may be poor advice for most people to take melatonin except for "shifting the clock" e.g., jetlag. Seeing extra light in the morning is enough to entrain the clock for most people.

[Terr_]

> but for winding down, you won't mess yourself up with dim light.

I have absolutely no scientific evidence in favor of its effect on sleep... but on a whim I picked up a yellow CFL bulb (originally advertised as not attracting bugs to your porch) and it makes a pretty nice lamp for reading in bed. If I go to another room of the house and turn on the light, I'm often surprised by how blue everything seems by comparison.

[Balgair]

To add here: One photon is not going to do anything and you can reason that out from 1st principles.

What is the 'noise' of your retina? How often do the nerves attached to your cones (the blue sensitive ones) just fire spontaneously? It's not 0 even when you are asleep. Just from some basic reasoning you can work out there is a noise floor that your body (each likely unique) learns to ignore. From what /u/herf here says, it's a log scale of input (similar to most detector systems).

From UpToDate: " Nocturnal melatonin concentrations can also be affected by drugs that interfere with the transmission of neurotransmitter signals to pineal cells (like propranolol, a beta-blocking agent) or those that inhibit melatonin's metabolism (like 8-methoxypsoralen), and by a few drugs that lack clear links to melatonin's synthesis or metabolism (eg, caffeine, ethanol).

Nocturnal melatonin secretion is also suppressed by a relatively dim 100 to 200 lux when pupils are dilated. The most potent wavelength for suppressing melatonin secretion appears to be 446 to 477 nm, which differs from the peak absorbances of the photopigments for vision.

Prolonged use of portable light-emitting devices (laptops, tablets, smartphones) before bedtime can have a negative impact on melatonin secretion, circadian rhythms, and sleep. One study compared the effects of reading an electronic book illuminated by a light-emitting device (LE-ebook) versus a printed book (by reflected light) for four hours prior to bedtime for five consecutive nights. Subjects in the LE-ebook group had suppressed melatonin concentrations in the early part of the night, a delayed endogenous circadian melatonin phase, felt less sleepy before bed, took longer to fall asleep, and reported feeling sleepier the following morning. These observations suggest that evening use of light-emitting devices may contribute to phase-delays in the circadian clock and difficulty initiating sleep."

Prehaps /u/herf could tell us about the study that looked at ebooks and if they used f.lux or not as a control.

UpToDate's cited sources are:

Mayeda A, Mannon S, Hofstetter J, et al. Effects of indirect light and propranolol on melatonin levels in normal human subjects. Psychiatry Res 1998; 81:9.

Garde E, Micic S, Knudsen K, et al. 8-methoxypsoralen increases daytime plasma melatonin levels in humans through inhibition of metabolism. Photochem Photobiol 1994; 60:475.

Wright KP Jr, Badia P, Myers BL, et al. Caffeine and light effects on nighttime melatonin and temperature levels in sleep-deprived humans. Brain Res 1997; 747:78.

Röjdmark S, Wikner J, Adner N, et al. Inhibition of melatonin secretion by ethanol in man. Metabolism 1993; 42:1047.

Ekman AC, Leppäluoto J, Huttunen P, et al. Ethanol inhibits melatonin secretion in healthy volunteers in a dose-dependent randomized double blind cross-over study. J Clin Endocrinol Metab 1993; 77:780.

Brainard GC, Rollag MD, Hanifin JP. Photic regulation of melatonin in humans: ocular and neural signal transduction. J Biol Rhythms 1997; 12:537.

Aoki H, Yamada N, Ozeki Y, et al. Minimum light intensity required to suppress nocturnal melatonin concentration in human saliva. Neurosci Lett 1998; 252:91.

Brainard GC, Hanifin JP, Greeson JM, et al. Action spectrum for melatonin regulation in humans: evidence for a novel circadian photoreceptor. J Neurosci 2001; 21:6405.

Chang AM, Aeschbach D, Duffy JF, Czeisler CA. Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. Proc Natl Acad Sci U S A 2015; 112:1232.

[herf]

Chang's eBooks study was done in 2010, after f.lux shipped but before we figured out who to talk to about it.

If you want to see fluence-response curves for single-wavelength lights, this is a really neat reference: http://www.cet.org/wp-content/uploads/2014/06/Gooley-2010-Sc... - this one makes the case for some cone interactions when people are sensitized to darkness.

And the mostly-consensus view on melanopsin response is presented here: http://lucasgroup.lab.ls.manchester.ac.uk/research/measuring...

[WalterSear]

>Note: measurable is not the same as deleterious, but flux doesn't even eliminate all the blue light your computer is putting out, let alone the other sources in your house.

[bsg75]

What is the result of the typical over-the-counter dose, often 3-5 mg?

[enraged_camel]

I think the effect is different for everyone. I personally have extremely vivid (and not necessarily pleasant) dreams when I take a 3mg pill. 1mg or less works great, though.

[heffo]

As with any medication, side effects vary. When I took melatonin, I would very quickly fall asleep but would still wake up extremely tired. I also experienced very severe depression when on melatonin, that started about 2 days after use, and ended about a day after stopping use.

I do know people that have had it work very well for them, however.

[WalterSear]

That hangover in the morning means you were taking too much, fwiw. If I were you, I'd experiment with much lower doses.

[heffo]

That's very possible, but the depression was severe enough that I'm not inclined to try again.

[eikenberry]

I found that the higher doses lead to me falling asleep fine but I tend to wake up in the middle of the night. I assumed the pill was getting my melatonin to high and when it went back to natural levels it triggered my waking up.

I've been using 1mg lately (the lowest I can find) and they work much better. Still help make me drowsy, but without waking up in the middle of the night.

[WalterSear]

I've found that 0.3 mg will have me waking up very briefly in the night, but that my sleep is still refreshing. I assumed that this might have something to do with the 'dual sleep' that humans are ostensibly supposed to have had, before electricity came along.

I recommend experimenting with amounts (I break my pills up) and finding the amount that works for you.

[tashoecraft]

It seems the only real study/evidence for the dual sleep idea is from one source and a separate study of 8 people. Sleep experts seem to suggest that now is is impractical and unlikely you will be able to adapt, because of how prolific electric light is.

[WalterSear]

Since it's a non-linear metabolic process, and relies on a specific level of increase over time, when it increases too fast (because you took too much), won't necessarily help you get to sleep. It will also give you a 'sleep hang over' in the morning.

You also have to take it an hour or so >before< bed.

[drzaiusapelord]

I take 5mg every weeknight as a insomnia treatment. I start getting sleepy about 45-60 minutes after taking it. If I fall asleep then, I'll sleep the entire night.