Sad lightboxes make me happy
September 28, 2006 4:21 AM   Subscribe

How does the kelvin and lux ratings of a light relate to how effective that light will be for treating SAD?

I have a 10,000 lux 7000 kelvin * lightbox that I use in the winter. However a new job with early mornings means I'd rather have somthing to use at my desk. I've found lots of desktop sad boxes but they're all huge and obviously alien to the workarea.

I've also found a supplier for mini flurescent tubes that fit in a anglepoise type lamp. 1700 lux and 6700 kelvin.

Does the difference between 10,000 and 1,700 lux means I'd need to use it for five times as long?

How important is the kelvin rating of the tube?

* I may be wrong on the kelvin rating of the lightbox I already own...
posted by twine42 to Health & Fitness (19 answers total) 4 users marked this as a favorite
The Kelvin rating (colour temperature) is probably the most important thing.

Colour temperature refers to (digging in my memory here) the equivalent colour in black-body radiation. Essentially, a black-body object heated to 7000K has the same colour temperature as your SAD box.

That said, i don't know anything about using light as a therapy for SAD. That said, 7000K seems a bit high; midday colour temp is about 5200K.

The simplest hack at your desk would be to take a regular lamp, and use colour-correction gel (a sheet of coloured plastic; try Rosco or Lee) to correct it to daylight.
posted by dirtynumbangelboy at 5:16 AM on September 28, 2006

Actually I have seen research that claimed that color temperature is basically irrelevant for using lightbox treatment, and that illuminance (which can be measured in lux) and exposure time are the only important factors.
posted by grouse at 5:37 AM on September 28, 2006

Sorry for the derail, but does anyone know the name of a condition that's the opposite of SAD? Just figured minds who know might be on this thread and it'd save a whole new question..
posted by wackybrit at 5:39 AM on September 28, 2006

Sorry for the derail, but does anyone know the name of a condition that's the opposite of SAD?

Opposite in which direction? An affective disorder but not seasonal? Seasonal but not an affective disorder?

posted by mendel at 5:58 AM on September 28, 2006

As I recall, the main concern regarding the quality of the light is if the infrared component is sufficiently filtered out (retinal damage) - it is in med grade lamps.
Also less lux = longer time needed. 10K lux = 30min. 5K lux = 60min.
This is also true if you move further away from the lamp. The lux rating is stated as X lux at a certain distance from the lamp (usually 30cm). for distances comparable to the size of the lamp, double the distance means (roughly) half the light (~ ½X lux).

Good luck with treating your SAD
posted by Thug at 6:02 AM on September 28, 2006

The theory is that your trying to replace sunlight.

Sunlight is very bright and has a wide, smooth spectrum. That's the key -- very bright, very wide.

I suspect that fluroescents wouldn't work as well, because they don't have a smooth spectrum.

The therapy I see citied is 30-60 minutes of 10K lux broad spectrum light, in the face, but not starting directly at the light. The idea is you are trying to replace the missing sunlight. If 10 hours of 1000 lux lighting could replace 1 hour of 10K lux lighting, then SAD would have gone away with the electric light. Since it hasn't, I'm assuming that intesity is critical to the treatment.

Buying something bright and wide spectrum might help you at the office, but for your main therapy, stick to the big light box in the morning. This may mean getting up earlier, which sucks, or you may be able to use the big lightbox in the evening -- there's some debate as to how critical using it in the morning is. Of course, if that shifts your sleep cycle the wrong way, you're trading SAD for Sleep Deprivation, which really isn't a good deal.
posted by eriko at 6:06 AM on September 28, 2006

I bought a lightbox around 8 months ago and I don't remember reading anything about difference in colour temperature being particularly important, although I do appreciate the fact that the light from the box is fairly broad-spectrum.

The main factor determining how long you need to use the device for is the lux rating - see the various options listed on this page for examples.

I will say that I also tried the Desklamp listed on that page and while it's a nice quality item you will need to use it for quite a long time for it to work. Their guidelines of 75-105 minutes use seem about right. Of course you may find that you can comfortably work and take the treatment at the same time.

It looks like you're in the UK; Outside In will give you a free 21-day trial of any light box which strikes me as a good deal.
posted by teleskiving at 6:11 AM on September 28, 2006

Outside In (I have one of their excellent Bodyclocks) also has a page debunking the need for full-spectrum lighting.
posted by grouse at 6:34 AM on September 28, 2006

Response by poster: Outside In are about quarter of an hour from where I live (assuming the Girton Interchange isn't solid) which is tempting.

The only problem is that the light boxes are £100 minimum while the daylight tubes are in the £20 region.

Cheers guys.
posted by twine42 at 7:26 AM on September 28, 2006

Response by poster: grouse : do the bodyclocks actually help? I've been somewhat skeptical of them.
posted by twine42 at 7:27 AM on September 28, 2006

twine42: it's a much easier way to wake up and go to sleep. I've found that I've been a lot less tired since getting one. This is probably either due to (a) the sunrise effect being a more pleasant way to wake up; or that (b) reading in bed while the clock is on sunset mode is an effective insomnia cure.
posted by grouse at 7:41 AM on September 28, 2006

I also have a bodyclock (the Sunray); it was about 60 quid and I think it's worth the money, if a bit plasticky. It's a good idea to get some blackout curtains to increase the effect - actually it's a good idea to get them anyway, sleeping in a really dark room is a lot nicer.
posted by teleskiving at 7:49 AM on September 28, 2006

Recent research shows that a newly discovered thrid photoreceptor (other than a rod or a cone) sends signals to hypothalamus, which regulates circadian rythms. According to one professor, "At certain times of the day we may want light that is richer in reds, and at other times richer in blues."

Interesting read and you might be able to dig up the acutal journal entires if you want a good fpp.
posted by |n$eCur3 at 11:20 AM on September 28, 2006

I got a bulb from Full Spectrum Solutions for the small fluorescent fixture we have for our desks, and it works great. If you have an incandescent desk lamp, you could try one of their CFL bulbs, too.

They're cheap, so that addresses your question regarding how to fit it in at work.

Regarding the lux and Kelvin of your fixture, you may find some information at Pubmed. Kelvin is just a measure of the "temperature" of your light, essentially the mix of colors it contains. There's not a great amount of research I'm aware of on the effects of different light temperatures. Most studies attempt to achieve the closest resemblance to daylight, and full sunlight is around 5-10,000 K, so it's a wide range. Changing 1700 K up at the range you're in, isn't going to have much effect, I wouldn't think.

Lux is the "dosage", but it appears that when you get it is at least as important as how much you get. In other words, getting up and taking a 30 minute walk in the morning helps both because you're getting light, and because you're getting it in the morning. This makes sense to be because what you're trying to do is to entrain your circadian clock. Go ahead and change the bulb in your desk lamp, but to really get the most effect, you need to get natural or full spectrum light when you wake up, too.

Note that of the non-commercial, methologically sound studies I've seen, the maximum effect you should expect is actually pretty small. It takes treatment and placebo groups around 100 subjects each to begin to find statistically significant differences, so I think the take home message is to get as much natural sunlight or simulated natural sunlight as you can, especially in the mornings, but don't obsess over details because they're not likely to make that much difference overall.
posted by Mr. Gunn at 6:05 PM on September 28, 2006

Sorry for the derail, but does anyone know the name of a condition that's the opposite of SAD?

Opposite in which direction? An affective disorder but not seasonal? Seasonal but not an affective disorder?

It seems that SAD is related to the lack of light (often called winter depression). Is there a name for the opposite? That is, 'summertime depression'?
posted by wackybrit at 9:25 AM on September 29, 2006

Is there a name for the opposite? That is, 'summertime depression'?

I've never heard of such a thing. Do you have any evidence that it exists?
posted by grouse at 9:38 AM on September 29, 2006

Just wondered. I wouldn't go as far as 'depression', but I feel many of the same things as an inverse of SAD. I love being in the dark and it makes me feel more alert and able to get on with things, but sunshine just makes me tired and fed-up. That's why I tend to stay up till 4am and sleep then. Works for me at least! :)
posted by wackybrit at 5:06 PM on September 29, 2006

Response by poster: I love being in the dark and it makes me feel more alert and able to get on with things, but sunshine just makes me tired and fed-up.

Ahh... that's called being a geek. :)

I do find it desperately ironic that when I was in my late teens I was nearly nocturnal spending my time drinking, coding and using various muds and talkers, but now I'm in my late twenties I get effected by the slightest dip in sunshine levels.
posted by twine42 at 9:57 AM on September 30, 2006

I'm 25. Perhaps the flip is due soon :)
posted by wackybrit at 10:48 AM on October 5, 2006

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