Archive for the ‘Darkness therapy’ category

Beam n Read hands free lamp with blue-blocking filters

August 10, 2015

If you are a quilter or crafter, you’ll know the importance of having good light to work by.  I have two spotlights over my sewing desk, which is fine when I’m working there, but when I get to the stage that involves curling up in bed or on the sofa with the quilting frame, I have a lighting issue.  Recently I discovered that some quilters wear head torches for this.  You look a bit daft, and anyone you lift your head to talk to won’t appreciate the sudden beam of light in their face, which I can manage.  What was bothering me was that the cold white LED shining right above my eyes wasn’t a great option if I wanted to sew in the evenings, in terms of avoiding blue light, and sometimes it would give me a headache.

After some hunting around, I discovered the Beam n Read.  It’s a lamp you hang around your neck, so that it points down onto your crafting or your book and not into the face of your startled partner.  You can get a version with 3 LEDs or a version with 6 LEDs, with a switch that allows you to turn on just 3 of them if you choose.  More relevant to this website, it comes with two snap-on filters that block blue light. One is amber, one is red.  The folks at Beam n Read very kindly sent me one for review.  It’s the 6 LED model.  There’s also a model with a magnifying glass, but I don’t get on with those so I didn’t request it.  Here’s their picture showing what they look like with the filters on.

BNR_LED6_ filters_W2b

It’s an ingenious little device, especially with the filters.  Some people want to be able to see more and can use the amber filter, some want the light to be dimmer and use the red filter, and some simply have a colour preference.  They don’t make any medical claims, of course, but it gives you the option to use task lighting that filters out blue light and thus shouldn’t disrupt your melatonin production.  Having a personal, focused light can be particularly useful if you are, say, reading in bed and don’t want to disturb your partner, or if you’re getting up to feed a baby and want to minimise everyone’s sleep disruption.  The elastic strap which goes around your neck is adjustable, and the lamp itself is sturdily built.  If you find that the 6 LED version is a bit bright on its own, you have the option of reducing it to 3 LEDs when it’s on white, and then putting it on 6 LEDs when it has the colour filter on, so that you don’t end up with a light that’s suitably coloured but too dim to see by.  The colour filters are great, they give a strong light in two useful and pleasant colours, and you don’t get any light bleeding around the edge.  The light seems to be about as strong as my Petzl Tikkina head torch, which is about right for me, neither too dim to work by, nor so bright that you get glare problems.  Being bigger (and heavier), it takes bigger batteries, so it’ll last a lot longer before requiring fresh ones.

Unfortunately, it just didn’t work for me.  As a child, I remember reading a book which said something along the lines of, “Owen’s parents realised he needed spectacles when they saw him reading with the book six inches away from the end of his nose.”  (I have no idea what the book was, but it definitely featured an Owen.  I think he was Welsh, and there may have been magic involved.)  I thought this was rather odd, as I have always held books that close or closer even with my glasses on!  It’s the same when I’m sewing.  From what my optometrist says, people who are very short-sighted like me tend to do this, and you end up finding positions for reading and sewing that work nicely for you without much trouble.  However, it means that having the light shining from the top of your chest, rather than from somewhere near your eyes, is absolutely useless.  I shortened the strap as far as it would go, and moved the quilting frame around, and wriggled.  Unless I sat at a really uncomfortable angle which I couldn’t sustain for long, I couldn’t get the light to do more than illuminate the bottom part of the quilting frame.  I found the strap rather scratchy as well.  Beam n Read mentioned that some quilters make their own strap, which may mean that there are a few other people having this problem, although it could just be a case of quilters wanting to make their own version of any textile in sight.

So then I tried putting it on my forehead.  The strap is too long for that, so I grabbed my trusty eye mask and put that on top of it to keep it in place.  That worked, but then it felt uncomfortable having that big straight block of plastic against my forehead.  A spare fleece wrist warmer worked for padding, and I managed to keep it on my head for long enough to work with.  I now had light coming from the angle I wanted, and I could change it to amber light in the evening so that it wouldn’t creep around the edges of my orange-tinted specs!  But the set up was quite ridiculous, it’s really not meant to be used that way, and before long it fell off.  I don’t have babies who need to be fed in the middle of the night with minimal light, or go camping, or any other uses that I can think of that would work for me.  Reluctantly, I gave up on it.  I think I’ll have to buy a second head torch and put an orange vinyl filter over it instead.

By this point I was eyeing it wistfully, as it’s a nifty device and I had really wanted it to work.  I brought it out to show my friends when they were around for board games, as they are crafters too.  The cross stitcher said it wasn’t for her.  The spinner is interested, and since they hold their spindle quite low down, it may end up working for them.  The knitter wasn’t there and hasn’t been knitting much for a while anyway.  My partner, who doesn’t do any of these things (though he does play a variety of musical instruments), is wondering whether he will be able to attach it to a bedpost so that he can read in the evening without having his rather large bedside lamp on and shining white light everywhere.  I suspect it won’t really work for that, but we will play around and see what can be done.  I’m sure there is someone I know who will find that it’s just the thing for them.

I can’t really give this one a rating, since whether it works for you will depend on whether you like having light coming from your chest rather than near your eyes, and what sort of tasks you will use it for.  If you reckon it will suit you, then it’s great.  The only thing I’d criticise is the strap, which I hope they improve in the future.  Apart from that, it’s the only device of this nature I know of which has orange and red filters, and it’s sturdily built, with a good battery life.  You can get head torches with an additional red light built in, but as far as I can tell, the red light on those is too dim for sewing or reading by.  I may give one of them a try just to see.

Advertisements

What colour should I use for darkness therapy?

February 12, 2010

By now you may be feeling rather overwhelmed by all the colours I talk about for darkness therapy.  Between my own visual comfort and what is actually available, I use products in a variety of colours.  The one thing they all have in common is that they either block/filter out blue light, or they product light which does not have any blue in it.  This means you can use yellow, orange, amber, red, or brown.  You may find that you have strong preferences concerning colour to the point where the wrong one for you makes you feel unwell, particularly if you have dyslexia, migraine, ME/CFIDS, Meares-Irlen Syndrome, epilepsy, and possibly severe myopia (short-sightedness).  Make sure you can try out a colour before committing to anything expensive.

Yellow

This is the lightest colour of the set.  When used to tint glasses, it increases contrast in a way some people can find disconcerting.  It’s often available as a standard tint for sunglasses, though be sure to ask your optician whether it blocks 100% of blue light.  I have seen some websites selling yellow lenses that claimed that they would work for darkness therapy, but this study suggests that they may not.

I’ve seen two shades of yellow used as a coating for incandescent light bulbs.  Most often it’s the slightly more orangey one.  The light is a little more orange than you’d expect from looking at the bulb coating, and may be described as a marigold yellow.  I personally find it very pleasant.

Reflector bulbs can be sold with a yellow coating, but unless you are going to be using tinted glasses as well, I don’t recommend these as the coating is only translucent and I think it permits some blue light to come through.

Fluorescent bulbs can be bought with a yellow coating as well.  I don’t know what they’re like as I’ve never tried one.  They’re often sold as “bug lights”.

Yellow is rarely used for LEDs, and on the two occasions when I bought something that was sold to me as containing yellow LEDs, they turned out to be a horrible orange.  I’ve been told by lighting specialists that yellow is a tricky colour for LEDs, which is why you don’t see it often.

Candle flames are mostly yellow, although these is a small amount of white light in there as well which may or may not be enough to influence your circadian rhythm.

Orange

This is the colour I chose for my tinted glasses, mainly because it’s directly opposite blue on the colour wheel and I already knew that I got on with it from using an orange monitor filter on my laptop.  Objects viewed through orange lenses appear golden yellow, for some reason.  I find it quite a pleasant colour for lenses, it doesn’t increase contrast, and as apparently is true for many people, it makes it easier for me to read.  The colour distortion may bother you, however.

Orange-coated incandescent lightbulbs are likely to be sold as “amber”, but the coating looks pinkish-orange to me.  The light is a fair bit darker than that produced by yellow-coated incandescent bulbs, being an orange that is almost closer to pink.

Orange-coated reflector bulbs are also usually sold as “amber”.  The coating is again translucent, but I think it probably cuts out most, if not all, blue light.  It’s not the best light source, though, I wouldn’t recommend it.

Orange LEDs are commonly used for appliances, such as on electrical sockets.  Again, there seems to be difficulty in getting a pleasant colour, although the light on my kettle is not bad.

If you wish to buy a salt lamp for decorative purposes, the thick layer of salt looks pink when it is not illuminated and glows orange when you put a bulb in it.  I suspect that a small amount of white light is still getting through mine, so I put in a pink-coated 15W bulb instead and it nows glows a deep salmon colour.

Amber and brown

Amber may be used to refer to orange, or it may be a shade of brown (orange + black).  Amber and brown are common colours for sunglasses, although it has been suggested that not all sunglasses which claim to block all blue light actually do so.  I have no idea whether this is true, I suspect that it may be a marketing myth, but again, check with your optician.

The main advantage of brown is that it doesn’t distort colour in the way that orange does, and the disadvantage is that in order for it to be strong enough to block blue light, it will be quite a bit darker than the equivalent orange.  I tried a pair of amber fitover blue-blocking glasses and not only did everything appear very dark through them, but they completely hid the parts of my face which were behind them.  My orange glasses do nothing of the sort.

Red

Red is the darkest pure colour of the set, and anything viewed by red light or through a red filter will appear monochrome.  This will be off-putting for many people.  On the other hand, there’s a school of thought that red is far more effective than orange or yellow for darkness therapy, so you may prefer to use it for that reason.  However, this site claims that “red is a very uncomfortable color to look through”, so you may prefer to restrict its use to light bulbs.

Red-coated incandescent bulbs exist, but I have not tried them.  You can also buy incandescent bulbs with red (translucent) glass called “fireglow” which will give off more light than the solid-coated bulbs, but I don’t know if the translucent coating is enough to filter out blue light.  Red reflector bulbs are probably similar to these.

Red LEDs are cheap to produce and give off a pleasant colour, so they’re commonly seen in remote controls and so forth.  If you want to use a bike light as the equivalent of a torch, it will probably be red.

Red glass is a popular option for tealight holders.  While the jury is still out on whether candlelight is acceptable for darkness therapy, I would guess that putting the candle into a red candle holder should be enough to compensate for the small amount of white light that may be present.

Darkness therapy

January 26, 2010

The idea behind this is that humans do best when they have melatonin being produced for half the time (averaged out over a year, it won’t be 12 hours all the time unless you’re living on the equator), and that it’s useful both for aiding sleep and for other things such as fertility and cancer risk.  I’m a little warier of claims that a yellow light bulb will fight cancer/get you pregnant than I am of the claims that it will improve sleep, so I’d treat that side of things as rather more speculative, but there does seem to be a fair amount of research backing it all up, if indirectly.  While darkness therapy itself may be fairly new, the various roles of melatonin have been studied a great deal by now.    There have been studies using 12 hours of complete darkness to treat bipolar disorder, but this is difficult to implement and is generally thought not to be necessary, though I’ve read a website by one guy who feels that it is essential and discusses washing up in the dark!  So while there appears to be a great deal of research on melatonin and sleep in general, for instance how shift work affects breast cancer risk, or on populations who do not have artificial lighting (and have many other major difference from industrialised countries), there is as yet little where researchers have directly studied darkness therapy by taking a group of people and changing nothing except the amount of darkness they get at night.  Hopefully this will be remedied before too long, although since there’s nothing in it for pharmaceutical companies, it may take a while.  All the research that I do know of can be found at LowBlueLights.com.

Since it’s blue light which affects circadian rhythms and tells the body that it should be awake and not producing melatonin, you can practise darkness therapy by simply omitting or filtering out blue light for several hours before you go to bed and while you are in bed.  There are a few ways of doing this, but the crucial thing is that once you have begun the darkness therapy in the evening, you do not get any white or blue light until the next morning, not even the tiniest bit.

Coloured light bulbs. For general use while awake, I prefer yellow-coated incandescent bulbs.  If you’re in the UK, they’re just sold as yellow bulbs.  If you’re in the US, they’re more likely to be called bug lights.  The bulb should be painted completely yellow, with a solid coating rather than a translucent one, and will produce an amber light which I find pleasant but which my partner, who generally dislikes coloured light, can’t stand. You can also get amber, red, or pink-coated bulbs, which you may prefer.  I’m not entirely sure whether the pink ones will filter out all blue light when used in an ordinary lamp, as I’ve only ever tried a 15W one inside a salt lamp, where the thick salt already filters out most of the blue.

Unless you live alone or are only planning to use these lights while alone (e.g. while breastfeeding or if you need to get up in the night because you can’t sleep), this is a potential snag.  As the coating is substantial, it will reduce the overall light output so that a 60W yellow bulb may be only as bright as a 40W white bulb, or even dimmer than that. You can buy fluorescent versions of these yellow-painted lights as well.  I haven’t tried them yet as I respond so badly to all fluorescent light, but I’m curious about how the yellow coating changes the level of visual comfort by filtering out certain bandwidths.  I tried buying an LED bulb that was sold to me as yellow, but it turned out to be a really nasty street-light orange; same goes for the two types of LED tea lights that I’ve tried.  I’ve been told by several lighting merchants that oranges and yellows are problematic for LEDs, it’s hard to get a pleasant colour.  I haven’t tried yellow halogen bulbs, but from the photos the yellow coating doesn’t look  strong enough to block all blue light.

For use when I’m going to the toilet at night, I bought a couple of red bike lights.  Since I’m an evening bather, showering was a problem.  I originally tried a red bike light, but while I can cope relatively well in near-darkness, it just wasn’t safe.  After puzzling over this for some time, I put a couple of lamps with 60W yellow bulbs on the hall, so that when the bathroom door is open, there’s a decent amount of light.

Even with coloured light bulbs, it’s best to keep the lighting in the evening fairly low.  At one point I had a 60w yellow bulb in a desk light by the bed for reading by, and a 25w bulb hidden behind a vase in the corner on my partner’s side of the bed for ambient background lighting.  Once I got the orange glasses, I eventually stopped using those, though I did acquire a salt lamp for ambient lighting which provides a nice orange glow.   (As far as I can tell,  the salt lamp filters out most blue light but not all, so you may need to get a coloured bulb for it if you’re going to be using it without tinted glasses on.)  If you do get tinted glasses, I’d recommend keeping on one lamp with a yellow bulb by the bed, for the occasions when you need a bit of light during the  night and don’t want to put your  glasses on.  There are various forms of gentle ambient lighting which are naturally low in blue light, such as candles or fairy lights, and for some people these will be an acceptable compromise.  If you go for fairy lights and you’re not going to be using tinted glasses, go for rice lights, which are a warm white, instead of LED lights, which are a cold light containing a lot of blue.  Unfortunately, I’ve found that even the small amount of light from fairy lights can be enough to halt melatonin production and keep me awake for hours if I don’t have my orange glasses on.  I may try “golden” LED fairy lights some time, but since all of the LEDs I’ve bought as yellow turned out to be a nasty orange, at the moment I’m using the salt lamp for my one yellow lamp.

Monitor filters. Computers and television screens emit an awful lot of blue light, and using them in the evening can really mess up your sleep all on its own.  Low Blue Lights and its friends sell expensive amber filters, but I simply got some samples of amber gels from a theatrical lighting company and cut them to size.  They stick on fairly well by static, unless you have the computer screen tilted quite far forward, and are easy to take off for daytime use.  I have a 17″ widescreen laptop and there are several inches to spare, so these would probably do you for up to 19″ or 20″ widescreen.  They’re a bit of a nuisance, they won’t work for larger monitors, and again my partner doesn’t like looking at them (some people just don’t get on with coloured light), but they’re cheap.  Brown filters should theoretically do the same job with minimal colour distortion if you can’t stand orange, though they will need to be fairly dark.

If you’re looking at a monitor through an amber filter or glasses, colours will be quite strongly affected.  The general effect is golden yellow more than orange, oddly enough.  Whites will be yellow, blues will be greens, everything will be a bit different.  This may annoy you, and it may restrict your activities.  I can’t do any quilting that requires me to select colours, and it’s not the time to go internet shopping for clothes.  This isn’t entirely a bad thing, as it forces me to wind down in the evenings and look at those hours during darkness therapy as relaxation time.

Tinted glasses.  There are two ways of doing this.  You can buy ready-made tinted glasses which will block all blue light, for instance from the range at Optima Low Vision, or you can get prescription glasses made up with a tint that will block blue light.  If you want to try standard sunglasses in brown, orange, yellow or red, check with an optician to find out whether they block 100% of blue light, as apparently most of them don’t.  You also want these glasses to provide good coverage, as opposed to some of the tiny lenses you can get these days.

If you’re going for anything expensive, try out darkness therapy with coloured bulbs and optionally monitor filters first to see whether you get on with it and whether it helps.  Since I can’t see without glasses, I decided to try some fitover glasses in amber which had the advantage of very good coverage.

Unfortunately I found them horribly uncomfortable, and they looked terrifying on me, being huge and so dark (much darker than the image shows) that my eyes were utterly obscured, along with half my face.  My partner and I didn’t want our evenings together spoilt by this, so I gave up on the fitover school of thought and had some prescription glasses made up instead.

On my optometrist’s advice, they were tinted with Wratten Tint 21, which is a pleasant orange.  Optical Express (who do some rather nice cheap frames) don’t do that tint as standard, but they could get that orange in 50% light transmission, which was more than enough to block 100% of blue light but still not so dark that my eyes were obscured to someone looking at me.  They called it 500 Orange 50%, and it cost the same as an ordinary tint. (Remember that brown is just orange with black added, so while they will look more conventional and may distort colours less, brown-tinted glasses will need to be darker.)  The glasses are rather fetching, if I say so myself, and I’ve had no complaints that they make me odd to be around.

I still keep the ambient lighting low when possible, as there will be a bit of light creeping in around the edges, and sometimes I put on the salt lamp so that the light is a soft orange.  However, I’ve spent enough time wearing these glasses with ordinary indoor lighting to confirm that they work beautifully in any conditions, and you don’t need to worry too much about what your light bulbs are up to.

I generally put on the glasses at about 9.30 for a bedtime of midnight, and have been using them for four months.  I’m getting sleepy earlier in the evening, sometimes I even fall asleep at 11ish, and I’m sleeping more solidly.  I’d estimate the effect of the darkness therapy to be similar to that of taking a sleeping tablet in terms of getting a good night’s sleep, but without the potential side effects or grogginess the next day.  I find the glasses very relaxing to wear.  If my partner comes home late in the evening, in the past I’d be so thoroughly woken up that I couldn’t get back to sleep for hours.  Now he’s lucky to get a coherent “hello darling” out of me, and I go straight back to sleep.  I haven’t had an episode of not being able to sleep until unholy o’clock in the morning, or waking up at night and not being able to get back to sleep for well over an hour, since I started using the glasses. There have been a few nights where I’ve forced myself to stay up until 2, yawning all the time, but where in the past (using bright light therapy alone) I would have messed up my sleep cycle by doing that and would be unable to sleep before 2 (or worse) for the nights afterwards, now (using bright light therapy, dawn simulation and darkness therapy) my sleep pattern snaps right back into place.  The only exception to this is the one night where I made the mistake of having the fairy lights on for half an hour around midnight when my orange glasses were off, as I’d hoped that they were yellowy and dim enough not to disrupt melatonin production.  The ensuing insomnia made me realise just how dreadful my sleep was in the old days, and how enormously it’s improved since then.

Are there any risks to light or darkness therapies?

January 26, 2010

There are risks to everything in life, but the risks for light and darkness therapies are minimal.  For starters, neither therapy interferes with medication, so that you may combine bright light therapy with antidepressants or darkness therapy with sleep aids if you need to.  Here are all the risks that I am aware of.

If you have macular degeneration, the current consensus seems to be that blue light may be damaging, though this appears to be largely theoretical.  This covers all bright lightboxes, as the ones which produce white light still contain blue light within the white, and in fact may contain even more light at the damaging wavelengths, which are actually below blue light.  You should probably avoid bright light therapy if you have macular degeneration, and will want to think about it carefully if you are at high risk of macular degeneration.  More information here, where the possibility of using green light instead is also discussed, and here.

Some lightbox manufacturers claim that their rivals’ products will cause untold damage in all sorts of ways.  Read the above link, which explains what’s really going on.  Short version: ignore them unless you already have, or are at high risk of, maculuar degeneration, in which case look into dawn simulation and/or darkness therapy instead of bright light therapy.  I find it extremely off-putting when manufacturers spread bad science in an attempt to knock the competition, but up to a certain level I think we just have to put up with it here, as they’re all doing it.

Bright light therapy may cause mania in bipolar disorder.  Read more about this here.  Changing the time of the light therapy may help, or just going for darkness therapy instead.

Traditional bright light boxes use very bright fluorescent light, and a number of people react poorly to fluorescent light (migraines, visual disturbances, nausea etc.)  Conditions which make this reaction more likely include migraine, ME/CFIDS,  MS, epilepsy, Meares-Irlen Syndrome, dyslexia.  Stay away from fluorescent lightboxes if you already know that you react badly to fluorescent light, and in general it’s a good idea to try before you buy with lightboxes anyway.

The other type of bright lightbox uses LEDs, either white or blue.  Some people don’t get on well with these either, although I think it’s a much smaller group.  Again, try before you buy, especially if you know that you’re sensitive to light. As the LEDs are displayed in a grid of little dots of light, some people report that they experience “spotting” in their vision.  It’s generally thought that these people were using the lightbox incorrectly, however.  It should be off to one side or above your field of vision, and you should not be staring directly at it.  This is how all bright lightboxes should be positioned, including fluorescent models.

For any problem relating to light sensitivity, you may be able to get past it by gradually increasing the brightness and length of time you spend in front of the lightbox, or using the lightbox for longer at a dimmer setting.  Take note of which lightboxes allow you to adjust the brightness if you think this will apply to you.  If you can’t handle bright light, consider dawn simulation and/or darkness therapy instead.

If you have ME/CFIDS or another condition which is highly debilitating, I now recommend making these changes gradually, just in case the shift in your sleep hormones sets anything off.  Start the darkness therapy one hour or even thirty minutes before bedtime, then gradually increase it.  Use a lightbox for short periods only to begin with, and on a dimmer setting if one is available and you are concerned about this.  I doubt that dawn simulation would cause any problems, but I’d suggest only introducing one change at a time.

A few people just don’t get on with coloured light in general or certain colours of light, including my partner, who reports reactions similar to the way I react to fluorescent lighting (including nausea).  This is more likely to occur if you have Meares-Irlen Syndrome and/or dyslexia.  Personally, although I have MIS I’m fine with blue and orange light.  It’s a highly individualised condition.  If this is the case for you, and it’s easily tested by buying a conventional coloured lightbulb that’s the same colour that you will be using, then go for a white lightbox instead of a blue one if you want bright light therapy.  Dawn simulation won’t be affected.  It may not be possible to practice darkness therapy fully, but at the very least you can dim the lights in the evening and avoid TV and computer screens.  Using brown-tinted glasses instead of orange glasses may work, as they don’t distort colours in the same way, although they’ll need to be fairly dark (brown is orange + black) to block blue light entirely.  There isn’t an option for coloured lightbulbs, but again, a brown screen filter for computers/TVs may be acceptable.

A disadvantage rather than a risk: if you do any sorts of art or crafts work, remember that colours will appear fairly different with a blue lightbox on and completely changed under yellow/orange lighting/glasses.  I try to plan my quilting so that I don’t need to judge colours for anything I do in the evenings, and have found that restricting my activities at that time helps me to wind down for sleep anyway.  Both fluorescent and LED white lightboxes give off rather a cold white light, which may make a difference if you usually use incandescent bulbs. I use a mixture of incandescent (yellowy white) and halogen incandescent (still a warm white but brighter than incandescent) bulbs on my sewing desk along with a white LED lightbox, and while I can see that the lights are a slightly different colour, it’s not causing problems in my work.

A friend of mine who suffers from depression and poor sleep reports that his mood drops significantly if he is in a dimly-lighted room, so if this is the case for you, darkness therapy is probably not an option.  On the other hand, this may be a short-term effect only.

Light and darkness: an overview

January 26, 2010

Arguably the biggest factors in sleep pattern regulation are light and darkness.  Humans evolved outdoors, getting plenty of strong daylight during the day and complete darkness at night, and averaging 12 hours of each.  It’s this light/dark signal that keeps the body on a 24 hour schedule: people who are completely blind almost all have sleep disorders, as the natural body clock runs on a 25 hour schedule for some bizarre reason and they don’t have the light/dark signals to keep it at 24 hours.  Now we sleep indoors, we mostly work indoors where the lighting is nowhere near as strong as sunlight, many of us barely get any   sunlight (and those of us with ME, or housebound due to other medical conditions, may not get any), and instead of following the natural pattern of darkness, we are in darkness only for the time we sleep and that may not even be complete darkness, and we will be under artificial light right up until bedtime.  This chart shows the relative light level from various outdoor and indoor conditions.  Even a well-lit office is still only 10% as bright as an overcast sky, and nighttime road lighting is 50 times as bright as a night with a clear full moon.  Our light/dark signals are all mixed up, and this is showing in the  high prevalence today of not only sleep disorders, but medical conditions which are affected by light/dark.

The very basic version is that bright light stimulates serotonin, and a lack of it can cause low serotonin levels and thus depression, as well as daytime sleepiness.  The main antidepressants used today are SSRIs, selective serotonin reuptake inhibitors, and there is a form of depression which is directly caused by low light levels during the winter, SAD (Seasonal Affective Disorder).  Cortisol is another hormone affected by light levels.  Melatonin is the hormone which makes us feel sleepy, along with a host of other roles in the body, and melatonin is produced when we are in darkness, which should average out to 50% of our time over the year but is now nothing of the sort.  The healthy pattern is to start producing melatonin a few hours before going to bed.  By using artificial lighting until right up to bedtime, melatonin production is inhibited, thus ensuring that we are less likely to feel sleepy when we go to bed, and also that we get less melatonin overall than we should.  All the research I’ve read agrees that we need to have melatonin coursing through our bodies for a certain number of hours per day, and that getting insufficient melatonin impacts on various areas of health, such as the immune system, as well as sleep.