I've seen blue light therapy systems which just look like a bunch of LED blue lights being sold online and in stores. They claim to help with sleeping disorders and jet lag.

How are they supposed to work and are they effective?

  • @Please delete me, I believe there is some evidence that avoiding the blue part of the spectrum before sleeping can be beneficial to certain circadian disorders. It is usually achieved by wearing blue-blocking (ie, yellow-looking) wraparound glasses in the evening, or sticking to incandescent rather than fluorescent lighting. I assume the blue light systems are intended to be used in the same way as the more standard (and better-tested) white-light systems, shortly after waking.
    – Lev Bishop
    Commented Mar 31, 2011 at 14:14

3 Answers 3


As far as I know the efficacy (and even safety) is as-yet unproven. However, there is a logic to why they might work:

  1. It has relatively recently (1990's) been shown that in addition to the well-known rods and cones in the mammalian retina, there is a third class of light-sensitive cells, known as photosensitive ganglion cells. (This was a big deal, because the accepted wisdom was that rods and cones were the only ones, and it took a while for this idea to be accepted);

  2. These pRGC are non-image-forming cells, and amongst other things, they are believed to be very important in synchronizing the circadian rhythm and regulating melatonin secretion from the pineal gland; and

  3. These pRGC cells have been shown to have peak sensitivity to blue/violet light, somewhere around 480nm.

Putting these facts together, you can see why people have concluded that the most efficient way to influence the circadian clock is using blue LEDs. But, as I said earlier, as far as I know this has not been proven either effective or safe.

  • This is very speculative. They might help, but we know most proposed treatments fail to be confirmed as clinically useful.
    – Oddthinking
    Commented Feb 14, 2013 at 5:30

Dr. Charles A. Czeisler, M.D., Ph.D., a professor of sleep medicine at Harvard Medical School, advises against LED blue lights at night time:

Huffington Post:

LED lights are particularly bad for our sleep because the intrinsically photosensitive retinal ganglion cells in our eyes respond more to blue and blue-green lights -- like the ones typically emitted by LEDs -- thereby interfering with sleep through melatonin disruption. However, he also noted that it's possible to change the color composition of LED lighting, so that the intrinsically photosensitive retinal ganglion cells in our eyes won't be as sensitive to it.


Solid-state white light is typically rich in blue light, and the colour composition matters. The ipRGCs are most sensitive to short-wavelength (blue and blue–green) light, so night-time exposure to LEDs is typically more disruptive to circadian rhythms, melatonin secretion and sleep than incandescent lighting.

But solid-state lighting could also provide some solutions. A solid-state white-light fixture can comprise multicoloured LEDs, so it is relatively easy to control not only the light intensity, but also the colour composition. The adverse effects of night-time light on sleep and circadian rhythms can be reduced by replacing blue-enriched light with red- or orange-enriched white light after sunset. Unfortunately, existing uses of this new-found colour control have tended to be wrong-headed: some airlines, for example, suffuse aircraft cabins with monochromatic blue light at night, the optimal colour for suppressing melatonin and disrupting sleep.

  • This explains why software like f.lux and redshift makes me go to bed earlier compared to keeping the default color temperature of my screen, thanks a lot @Franck! Also, why do I seem to see you everywhere? Don't you have a PhD to pursue? :)
    – erb
    Commented Jan 28, 2014 at 18:56
  • 1
    @erb Using some software to adapt the monitor's color sounds like a cool idea! Yeah a PhD is a succession of questions and, sometimes, answers :) Commented Feb 16, 2014 at 23:09

Here is a fairly detailed scientifically reviewed article which describes how light therapy can help with sleep and awakeness

Illuminating Rationale and Uses for Light Therapy.

Blue light around 460nm promotes wakefullness. It works by resetting the human circadian rhythm. Originally light therapy used high intensity white light but blue light at 460nm was found to more effective and at much lower lux levels.

  • 1
    I skimmed that article looking for some appropriate quotes to support an answer. It seemed to be rather lacking. There were lots of qualifications "Despite limited evidence", "Information [...] is, however, very limited." There were discussion of conflicting results. There were lots of weasel words: "Light therapy has been used to treat a number of disorders" is very different to "Light therapy CURES a number of disorders." I didn't come away with an impression that phototherapy was clinically proven to help sleeping disorders - merely that it had potential.
    – Oddthinking
    Commented Feb 14, 2013 at 5:35
  • i read illuminating as illuminati Commented Feb 14, 2013 at 11:43

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