Light Therapies For Depression
(Don't do this on your own. There are risks, described below. But these risks are almost certainly much smaller than those of medication approaches. )
Chronotherapy: an entire package of treatments for depression using light and sleep shifts
Why? How much light are you getting?
Light therapy can treat more than just winter depression, though that's the main use. Here's why: the amount of light reaching your eyeball from interior lighting is far less than the amount from the real thing. So unless you are outside much of the day in the winter, you are relying on electric light for your photons (in summer, there is so much light, most people get enough, even if they are indoors during their work hours). The following graph shows you just how much less light you receive, indoors versus outdoors (Lux is a standard unit of light flow):
|Candle light at 20 cm||10-15 Lux|
|Street light||10-20 Lux|
|Normal living room lighting||100 Lux|
|Office fluorescent light||300-500 Lux|
|Halogen lamp||750 Lux|
|Sunlight, 1 hour before sunset||1000 Lux|
|Daylight, cloudy sky||5000 Lux|
|Daylight, clear sky||10,000 Lux|
|Bright sunlight||> 20,000 Lux|
Bottom line: the outdoors on a sunny day is 500- 1,000 times brighter than office or room lighting.
(Source not verified; this table ought to be close enough for comparison purposes, though.)
Okay, with that as an introduction, let's look at light as a treatment for depression.
Warning: Safety Not Established (risk in macular degeneration, and possibly advanced diabetes, unclear))
A group of light therapy experts maintains a Forum for discussion of various issues, including eye safety. As of 2011, the consensus as I interpret it, seems to be that if you're not already known to be at risk for an eye problem, then the treatment should be considered safe.
On the other hand, if you have a condition that makes your eyes very sensitive to light, you may need to use caution with light boxes of all kinds (not, presumably, dawn simulators, described further below). Likewise, if you have a family history of such problems, e.g. macular degeneration (but also including several other skin problems such as actinic dermatitis), some caution might be necessary. It was recommended that you consult an ophthalmologist before using a light box.
One expert who specializes in this issue says that people with diabetes who already have eye problems from it should not use light therapy. I've not seen anyone else make such a firm statement but this is a well-known expert on this topic. Some others disagreed, noting that if an eye doctor has not already recommended avoiding bright sunlight, then a light box, should be okay. I don't think this question is settled.
If you're not satisfied with this summary, I have prepared an extensive discussion of light therapy and risk of macular degeneration (it's long). For that, see the Whole Story below.
Use Light Differently in Bipolar Disorder? Understand the Risk, Understand Your Diagnosis
If you already have figured out you have some degree of bipolarity (Bipolar II, soft bipolar disorder), then before you read on you should probably read about Bipolar Disorder: Light and Darkness. Then come back here to learn more about light therapy, starting right here -- because light therapy may need to be different in people with bipolar disorders.
If someone who understands how to look for it has already help you determine that you do not have bipolar disorder, you can skip to the next section. Mind you, it is not easy to be certain about this. If you have any doubt, read more about "bipolar II". You definitely should do this if you have someone in your family with a bipolar diagnosis.
Light Therapy in Bipolar Disorder
Light therapy is probably one of the safer antidepressant treatments for bipolar depression. Low "doses" can be safe for many people. But too big a dose can cause manic symptoms, just like any other antidepressant. So you have to be careful. Have your doctor help you find a safe dose -- one which does not produce any "manic side" symptoms or interfere with sleep.
While you are at it, consider the following recent research finding. In a very small study, 6 out of 9 women with severe bipolar depression showed a clear response to light therapy.Sit They did not have "seasonal" depression, but rather bipolar depression (although the season of the year in which the data was collected was not reported, to my recollection ). Here's the important finding: morning light may be more likely to trigger manic symptoms, leading to a "mixed state" of manic and depressed symptoms at the same time, than midday light. Interestingly, this almost exactly repeated the results of an earlier similar study, also with 9 women.Liebenluft
Following the usual protocol for life therapy, using it first thing in the morning (30 minutes before their usual wake time, in this case) three out of the first four women in this study developed mixed episodes (irritability, elevated energy, increased activity, creativity, aggression, racing thoughts, pressured speech). Based on that experience they changed the protocol so that everyone received light in the middle of the day instead. With this arrangement, four were full responders, meaning a complete or near-complete cessation of depression symptoms. Two others were "partial responders", clearly improved but not fully.
Therefore, for the moment, the optimal timing of light therapy for people with bipolar depression is uncertain. For safety reasons it may be wise for people with bipolar depression to begin with midday light rather than morning light, switching to the morning if no improvement is seen. However, because this was such a small study, it is really too early to reach a firm conclusion on this. A standard approach to light therapy, using morning light, it is not unreasonable. One just has to watch out for the emergence of mixed symptoms as detailed above.
Update 2012: finally, a larger study of the use of light therapy in bipolar depression. Unfortunately, this study says "it doesn't work". Well, it helped, but not more than a placebo, in part because in this study the placebo response was huge.Dauphinais So what does this mean for use of light therapy for bipolar depression? Taken together with the 9-woman studies above, I'd say "well, it's not a dud, but it doesn't work very reliably in bipolar depression. I wouldn't rule it out, but it's not a very sure thing". Remember, many people with bipolar disorder also have seasonal changs in mood, for which light therapy could be useful. But on the whole, one thing is clear: much safer --and cheaper and far simpler -- is to start with a Dawn Simulator.
How about a head-to-head competition between light therapy and a typical antidepressant; wouldn't that be one of the better ways to demonstrate that light really works to treat depression? Just such a study was recently published: about 100 patients in Canada, with depression in the winter, randomly assigned to either fluoxetine (formerly Prozac, now generic) or a standard light box.Lam
Here's what happened -- equal improvement in both groups, with light a slight bit faster in lowering depression scores (lower is better) at week one; fluoxetine in red, light therapy in blue; improvement is shown as a reduction in depression scores:
How about that? Light therapy is as good as the standard antidepressant approach. With fewer side effects and much less overall risk (not zero risk, but less).
If you're not familiar with light therapy for seasonal depression, more information follows below. Basically one sits in front of a box the size of a small suitcase (smaller ones now available; more on that below too) which emits a lot of light, for about 30 minutes to start, and as little as 15 minutes or less later to stay well through the winter.
The Canadian research is one of the most recent of several well-designed studies which when viewed together suggest that light therapy is an effective treatment for depression, roughly equal to medications in strength.Golden
So, if light therapy is that good, why isn't it more widely recommended? For one thing, early research on light therapy was poorly funded and thus often of very weak design. Placebo comparison ("control" treatment) is hard to do. Think about it: how do you put someone on a "placebo" treatment that seems like light therapy but isn't likely to do anything? It's not like making an identical placebo pill. Researchers have used dim red light, mis-timed white light, and negative ion generator boxes as "plausible" placebo treatments. All of these control treatments have their problems.
Furthermore, as one of the leading researchers pointed out, everyone in the study is likely to get some additional light exposure just from seeing the sun once in a while. In Seattle, where Dr. Avery works, that might really be once in long while, in the winter! But if all patients in a research study are getting some sunlight during the day, at random times during the study, that ought to minimize the difference between the "treatment" group that is getting light box treatment, versus the "control" group that is getting something else. As Dr. Avery says, it's as though you were trying to research on Prozac, with one group on the drug and one group getting placebo, but unknown to you, now and then someone was sneaking in and putting little doses of Prozac in the water supply of everyone in the study!
Because of these design problems, and the lack of a major industry to fund research on light treatments, early studies tended to be weak and contributed to the sense that light therapy itself is a weak treatment. And yet the two reports above (one a new study, one a good recent review of previous research) show that light therapy for seasonal mood shifts is not a weak treatment at all. And it may have similar strength even for non-seasonal depression. One study even found that hospital stays for depression were three days shorter for patients whose rooms faced east (thus getting regular morning sunlight), instead of west .Benedetti
Best of all, it is relatively cheap: the newest light boxes cost as little as $130-150 (a link in a moment). Compare the price of medications for a year, plus doctor visits to manage those medications. And it appears to be very safe. There is no evidence of eye problems in regular users after 5 yearsGallin ; there are no medication interactions; and there are almost no side effects. Some people get headaches, some have some eye strain. But the main worry with light therapy is that it will work too much like a regular antidepressant: as with other effective antidepressant treatments, there are numerous reports of hypomania developing during light treatment. One of my patients got a speeding ticket after sitting in front of her box too long -- twice!
Because of this risk, which includes mania Chan and even suicide Haffmans, you should not attempt light treatment on your own. This must be conducted with your physician as part of the treatment team, which includes planning for managing worsening during treatment. Do not do this on your own.
Basic Information About Light Therapy
There are plenty of sources you can go to on the 'net for this. Read on down this page for more details about bipolar depression and light therapy, and about specific treatment options; but if you need to start with some basics on light therapy, here is a site which will help you to:
- Understand Seasonal Affective Disorder (SAD)
- Understand the principles of treatment with light therapy
- Learn about light boxes and how to use them
Meanwhile, here is one of the most interesting research findings I've come across in a long time. People with seasonal mood changes have different responses to light in the winter, compared to summer -- in their own retinas!Lavoie So whatever "Seasonal Affective Disorder" is, one thing is for sure: it has a biologic basis. (For more on the biologic basis of depression, see my essays on the Brain Chemistry of Depression).
(comparison list of dawn simulators)
Hold on a minute, before you go tearing off looking at light boxes (discussed below)... There is a far simpler way to do light therapy, which is even cheaper and so far has not been associated with hypomania or mania, the primary risk with a light box (literature search 9/2005; still so,to my knowledge, in 2011). And it's cheaper too. It doesn't work for everyone who responds to a light box, but if it did work for you, it's clearly a better way to go.
What is a "Dawn Simulator"? This is simply a device to gradually increase the light in your bedroom in the morning, while you are still asleep. Try this: close your eyes and look toward the light by which you're reading this. You can tell where the light is, even with your eyes closed. A dawn simulator gradually turns on your bedside lamp in the morning, before you wake up, so that your retina (not you -- you're still asleep!) "sees" the light show up at the time you choose, increasing gradually just as natural sunlight does, over about 30-45 minutes. It's really nothing more than a timer and a rheostat (a device to slowly change electrical current) hooked to your bedside lamp. Note that this approach does not require a "light box".
Why is the gradual appearance of morning light potentially "antidepressant"? Think of it this way: the dawn simulator is trying to convince your brain that it's still July out there (even in December). It turns out that your brain knows what season it is primarily by the time at which morning light appears (okay, it's true, you can also tell the difference between snow, sleet, ice, freezing rain, and the warm summer sun; but evolutionarily, it looks like the brain's timing was set by factors more closely associated with light.) We think that some people are built to slow down in the winter, something akin to hibernation. Think of a hibernating bear: sleepy, slow, hungry for carbohydrates, unhappy if awakened, grouchy, grrrh. Those are pretty close to the experience of "winter blues" for some people.
So, if those peoples' brain could be tricked into thinking that it really isn't winter after all, might that prevent this shift toward a kind of half-hibernating way of dealing with the world? It appears that for some people, this actually works. In the recent research review (Golden meta-analysis, above), dawn simulator treatment was found to have an effect of similar size to light box treatment in 5 studies. In other words, the dawn simulator seemed to have as much power to improve mood as a light box. However, all of these studies were all from the same research group. Although Dr. Avery's research group is one of the best in the business studying light therapies, it would be nice to see someone else able to get the same result. Dr Avery is a passionate, kind man; maybe he and his team are so good at helping people believe a treatment is going to work, they could make throwing Frisbees an effective treatment for depression. If somehow they weren't so convincing when selling the control treatment, that could create this result all by itself.
However, dawn simulators are cheap, and there is no evidence for doing harm. So, if there is even pretty good evidence of effectiveness, this is worth considering. Here's a separate page on dawn simulators for more details on models, where to find them, how to use them, and so forth.
Which Light Box Should I Buy? (revised October 2014)
You can choose from "certified" or "cheap". You can also get yourself really confused by looking at "blue-only" lights. And if you read a lot about light box safety, you'll get yourself pretty bewildered, I think. That's where I am now on both the safety issue and the "which one?" issue.
Yet you are wanting to try one now, so you need some guidance now. Okay, for now, I think it boils down to getting either the official research-tested rig or the cheap one that in principle ought to work as well, if you use it properly.
A. The official research rig
Amazon --Spring 2012: $113, free shipping (this used to cost $350 only a few years ago...)
Notice that the light box which comes with this stand is higher than her eyeball, and it's LARGE, so if she moves her head a little the amount of light she sees will not change too much. That's the crucial difference, comparing the next option.
B. The Cheap route -- don't go this cheap! see the next option below
At $50 (Amazon) the Lightphoria is less than half the price of the Amazon version of the Uplift.
But even though they say it puts out 10,000 lux just like the Uplift, you'll have to get this one about 6" from your eye to obtain that intensity, whereas the Uplift box can yield that result at 12 inches. In either case, as you can see, they need to be close. You can also see that a small shift in the position of your head will reduce the light you get from this little one. If you must go this route, be careful to put something really interesting in front of you while using this treatment, so you won't move around too much. The box does not need to be straight in front of you. The ideal position is shown in the Uplift photo above. it could also be in your field of vision but off to the side and up a little (e.g. on a pile of books very close to your head).
C. Cheap, but better : NatureBright.
$68 at Amazon.
It's small, but not too small. It's got negative ion generator as well, which some research says may be helpful by itself. I haven't used this one but it's got better reviews at Amazon than the one above, which I have used, and that one is just too small.
This one has blue light so if you're going this route, you'll need to read the next section too.
Blue light boxes?
As you may have read, blue light is wavelength that sets biological rhythms, including sleep/wake cycles in humans (here's the Whole Story). So back around 2005, some companies started making little blue light boxes. They could be smaller because they were emitting just the "active ingredient" in white light. But now:
a) they're not the cheapest anymore
b) there is controversy as to whether blue light boxes, or little light boxes, are as effective as large white ones.
If you want to be really sure you have the same box that most of the research studies have used, you need the LARGE WHITE one above. Mind you, there is a research study showing that a little blue box is better than a placebo.Glickman Butt that blue light box now costs $100, and with it you get tangled up in both debates: Are blue boxes as good as white? Are little ones as good as big ones?
Finally, yet one more debate gets hauled up about the blue boxes: Maybe they aren't as safe as white ones even though at least some of the white ones put out even more high-energy light (higher than blue) than the blue boxes. Several light therapy experts have put forward this concern; not sure why yet. One of them seems rather invested in white light for reasons I don't understand entirely (and would welcome further enlightenment, so to speak).
What do I recommend for my patients? Not sure right now, as of 2011, because the little white one above just showed up. Before that I was using the little blue one because it was less than half the price of the big ones. But the prices of the big ones are coming down, and the blue one went up, and this little white one appeared!
*What about a visor approach?
If you have $200 to drop, not just $50, you might consider a green light visor, but only if you have to be walking around at the time you need the light therapy. If you can be sitting down at the needed time, the expense is not worth it, and the data supporting it not substantial enough (yet, anyway; as of 2013). You can't easily read or use a computer, though it's not impossible (my experience; versus an aviation study that panned the visor approach). You definitely cannot drive with this rig on.
Does the visor approach really work? The manufacturer offers four studies showing effectiveness versus control treatments. Unfortunately, none of the these has been published, near as I can tell (search by author or key word, e.g. green or visor or light, Pub Med, 12/2008). That should be a red flag. Yet green light has been shown effective in other published work, using a light tower -- much more expensive, not portable -- instead of a light visor. So even though several large studies with white-light visors did not show benefit versus control treatment (Teicher; Rosenthal), we now know the active ingredient in all that light (blue or blue green; here is the whole story about blue light). So theoretically the green visor might work, even if it does not have published evidence. Therefore you might consider it if you can't sit for light therapy (e.g. busy parent in the morning?). You look kinda funny with this visor on your head, though: I got quite a few laughs wearing it around the hospital. So this may be a privacy-of-your-own-home thing.
UPDATE 2014: There are now other visors out there. One of my patients came in with a pretty stylish Scandinavian number. But still no randomized trials and they're still quite expensive, about double the lightbox in C above.
I have to put the light box above my eyes?
Yes. The same team that developed the first blue light box also did an interesting experiment. They put a special helmet on patients undergoing light therapy, which allowed the light to hit only the top of their eyeballs, or the bottom. Why they thought this might be important, I don't know -- but they were right. It turns out you need use a light box positioned above your eyes, so that the light hits the bottom of your retina. Patients in the group with light hitting only the top of their retina did not respond as well to the light therapy.Glickman
Huh? Actually, think about it, this makes a lot of sense. Why would your body bother putting receptors for light at the top of your eyeball? The light you're interested in is coming from the sky, not the ground, right? Evolutionarily they'd be much more useful at the bottom of the eye; why waste them at the top where they can't "see" the light they're supposed to be telling the brain about?
The point here: don't put that light box on the tabletop next to your bowl of cereal and your newspaper. Put it up on something so that the light is coming down toward you (not very far away though: one foot for the big righ, and 6 inches for the little white box). I've been telling my patients for years to put their big suitcase-size light boxes on the table. Wrong. The little blue one ought to be easier to put up there somehow. A reader says he just taped his Zadro (now Omega) unit to the wall above his desk at work! (Thanks, Sean)
What Time Should I Use It?
Light can be used for several purposes, including winter depression, which is one version of seasonal affective disorder -- SAD, what an acronym. It can also be used for moving your sleep timing, even if you don't have depression. Here we'll focus on SAD.
For winter depressions , research has so far focused on using light therapy in the morning. Most studies have shown this to be more effective than evening light, when one timing is compared against the other and no further information is gathered about the patients participating.
However, things are getting more complicated now -- which in this case is good. There may be a way to make the timing more personally tailored. Indeed, it appears that some people may do better to use light therapy in the evening. You see, exactly how light therapy actually treats depression has not been fully established. However, excellent research in this area has begun to suggest that light therapy works by re-setting your biological clock timing (your "circadian rhythms") toward where it should be. For some people with SAD, their timing can be set to something closer to July rather than where their body seems to go in November through February!
This research uses language that can be difficult to understand (said I, using my own difficulties with it as a guide -- maybe you'd find it easier to follow than I have. If you're up for it, here's a recent review by leaders in the field). It speaks of the timing of sleep compared to when your melatonin begins to go up in the evening. To make things easier, though, Dr. Terman's group has produced a system for telling you when to use your light box.
Their research suggests that light therapy may work best about 8-9 hours after one's body starts secreting melatoninTerman. This hormone is associated with sleep, and the time at which it stops being produced may be one of the most important signals to the rest of your body saying "it's daytime now, time to get up!". When is your melatonin onset? What time does your body start its sleep cycle? One way to tell, according to Dr. Terman's group, is to use a questionnaire they developed to determine whether you're a "lark" or an "owl" -- a morning person or an evening person. I'll bet you have some guesses!
They call it the Morningness-Eveningness Questionnaire (MEQ). Brace yourself: if you're an owl, you might be able to start your morning light therapy as late as 8 or 9 am and see full benefit. But if you're a lark, there is some evidence (not conclusive yet) that you should be starting your morning light treatment as early as 4 a.m.! Instead of trying to determine your hour of melatonin onset, and calculating 8-9 hours later as your light time, you can take the questionnaire. If it says you're really a morning person, you may see more benefit from your light therapy by pushing the treatment time earlier, toward say 5 a.m. anyway.
The Morningness-Eveningness Questionnaire
This system is linked to a research process: your answers may benefit others.
For more extensive information about light therapy in a question/answers format, see the FAQ from the Center for Environmental Therapeutics.
Chronotherapy: an entire package of treatments for depression using light and sleep shifts
Chronotherapy puts light therapy together with sleep therapies to create a complete package treatment for depression that can replace or add to medication approaches. The ingredients include:
- "wake therapy"
- "sleep phase advance"
- a light box
- a dawn simulator
You've already learned about light boxes and dawn simulators above. For more on the first two ingredients, see my page on Chronotherapy.
STOP HERE ! WARNING: excruciating details below...
Review what you just read:
Chronotherapy: an entire package of treatments for depression using light and sleep shifts
The Whole Safety Story
(Revised 12/ 2011)
Light is good for mood, for some people, delivered in the right way. That much is clear, as you've seen. But a lot of light is also bad for some eyeballs, especially if it arrives in the form of blue light, because it can damage the retina in some susceptible individuals. Worse yet, it's not clear who's at risk for this damage, and who's not. However, the good news is that light boxes are less risky than the sun, it appears. (Update 2007: this issue is still under debate, although I cannot tell if the concerns which remain are motivated by concern for the public good, or by a desire for financial gain on the part of manufacturers of products which do not emit blue light. More on that in the 2007 update at the bottom of the page.)
In the following analysis, remember the bottom line from the simple version of this information that begins this webpage: one of the best known authorities on light boxes and their possible effects on the retina is on the record, as of September 2006, saying there is no evidence that they pose a risk.
The problem with a lot of light, especially with blue light, is a condition called macular degeneration. The most common version of this condition, which appears to be related to the amount of light hitting your retina over many years, is called "dry" macular degeneration. Fortunately, this is a problem which takes years to develop. It also appears that not everyone is susceptible, but I haven't heard yet how one might tell if one was among those at risk. Here's a good site with a lot of information about macular degeneration.
This issue of eye safety cranked up recently with the arrival of the little blue light box. Back in 1992, a team of light researchers estimated that it would take 72 winters of daily 30-minute light therapy to reach the threshold for causing eye damageWaxler But because the blue box puts out a wavelength that is theoretically more harmful than other wavelengths, there's been a lot of interest in the safety issue lately. Ironically, the graphs below suggests that if anything, the blue box is safer than "full spectrum" or all-white units.
Output of Energy, By Wavelength: "Full-Spectrum" Unit Output of Energy, By Wavelength: Uplift Unit
From left to right on this graph are the colors of the visual spectrum of light (part of the larger "electromagnetic spectrum" which includes ultraviolet, which would be off this graph to the left; and infrared, which would be off this graph to the right). The color band below the graph is supposed to be roughly positioned to match the wavelengths shown in the first graph: for example, blue is between 450 and 500 nanometers.
The black curve on the left graph is sunlight. The blue hump is the output from one of the little blue light boxes. The red and green curves are two different "full spectrum" light boxes, and the one on the right is the Uplift unit described above. As you can see, all the light boxes put out a lot less energy than summer sunlight (if you measured outdoor light in the winter in the northern part of the United States or Europe, that black curve would be much lower on the graph, in some places near or even below the output of the light boxes).
Notice that the blue box output (areas shaded in blue) has a relatively low peak, especially compared to sunlight. Second, note that the full-spectrum light box has two peaks below the blue hump and the Uplift has one big one. If there is any danger involved, which is at this point not really an open question, at least according to one of the world's experts on the subject, then these blue peaks from the "white" boxes peaks are more dangerous to the retina for two reasons: first, these peaks are at a lower wavelength, meaning even higher energy; and secondly, they are larger (taller), meaning more energy as well. (A reader sent me a nifty trick: get a Chroma Green filter (expensive!) -- see #389 on that linked page -- and put it over your old light box to create an output pretty close to the little blue box, just a little to the right, still at low enough wavelengths to get the desired effect on the circadian photoreceptor, presumably. He's testing that this winter. Thanks, HR).
What about a green light approach? What if you just got pretty close to blue, close enough to stimulate the retinal receptors that are connected to the biological clock (explained in the story about why blue light is the one that matters)? Could you get the desired antidepressant effect with less risk (presuming there really is a risk; remember, that's not been established)? This is an approach being tried by another light box company; and of course they're making a great deal of noise about the risk of blue light, since that approach is what they are now competing against. For example, there is one frightening story from the green-light company about one patient. When I sent this to Dr. Sliney, he reviewed the case again and points out that the retinal changes were in the very center of gaze ("macular"), which would imply that the patient was staring directly at the light box, were that to have been the cause. Patients are generally instructed not to do this, and it would be physically difficult to do so long enough to cause this kind of damage. More likely, in Dr. Sliney's view, is that this case represents damage from the sun, despite the suggestive timing, in part (my interpretation of his reply) because we know the sun can do this, whereas there is no clear evidence otherwise that light boxes can. A bit circular, I grant you, if I've interpreted him correctly. At minimum we might conclude: don't look straight at your light box. Read the newspaper or write your mother a letter. (Revised 11/28/06)
Finally, if you need the reference, Dr. David Sliney's statements at the very top of this page are found in the Proceedings of a symposium on Lighting and Health, held in Ottowa in 2006. Dr. Sliney was the featured speaker on this safety issue. The meeting abstracts are not online as of this writing (10/2006; Dr. Sliney kindly sent me a copy).
More safety details, 2007
Murray Waldman, maker of the low-intensity green light box from Sunnex Biotechnologies, continues to send me information raising concern about blue light exposure and the risk of macular degeneration. As of mid-2007, it still appears that the principal basis for this concern is the recognized correlation between the amount of sunlight exposure as a youth and young adult and the risk of macular degeneration many years later. I cannot tell whether his continued concerns about blue light risk are motivated primarily by his financial commitment to an alternative approach. He probably could not determine that either, though he is very firm and forceful in his logic and his references to existing data.
As far as I can determine at this point, this correlation is the sole basis for claims that you will see by manufacturers of products which are competing with the "little blue light box" , which is the light box I used to recommend to my patients (primarily because its cost was so low relative to other options; I have no financial connection). For example, the NatureBright product using a white light advertises "no blue light which may cause vision problems such as macular degeneration". But the NatureBright light has not been directly tested in randomized trials, as best as I can determine from their website. It certainly has not been shown to be "twice as effective" as other light therapy products, which is such an overstatement that you might want to avoid using this product just to punish them for misleading advertising (I believe the claim is based on some data suggesting that a combination of a dawn simulator and a light box is better than either alone; but this research did not use their product specifically). It still might be the best product, because it is now so cheap, and combines the light box and the dawn simulator, a very nifty feature if you're stuck in bed, but probably a bad idea overall (get up with the dawn simulator and use the light box over your breakfast!) We would want to see how much blue it puts out, and other wavelengths as well, just like the graph above, if we really believe that blue light exposure from these products presents a risk to the retina as one ages.
Final safety thoughts
Here's my view: some people are at greater risk of macular degeneration than others, surely. Those at least risk could probably go outdoors all day every day until they are 80 and be okay. Those at high risk would end up with damaged retinas from that much exposure. Now, trade some days of being outdoors all day -- like people used to do, farming for example -- for 30 minutes in front of a blue light box. Do we really think that's worse than having been outdoors? I would think that indoor light therapy represents less risk than people used to get from working outside. However, there are probably some people who were at risk of macular generation before, working outside, and are at risk now if indoors they add a blue light box. At least those who are at the very upper end of the risk curve might have something to worry about -- for example, those with close relatives who had early, severe macular degeneration.
What does this mean? Well, if someone in my family had macular degeneration and I needed light therapy, I might buy one of the Sunnex boxes. But I'd probably try the visor green-light system first to see if it worked! Presuming I have the money for these more expensive routes. If not, I'd buy the $60 Lightphoria and use it enough to treat my depression (if it didn't work I'd sell it to my psychiatrist for a demo'). Once I was better I'd try to lower the amount of time I used it, very gradually, until whoops, the depression was coming back. Then I'd go back up in duration of light use per day, just a little, trying to find the "sweet spot": the shortest fully effective period of use.
Why? Because I'd rather be treated now and hope for a better solution in a few years, versus avoiding a potentially cheap solution on the basis of a theoretical risk that if I used this treatment another 10-20 winters I'd have done some damage to my eyes.