Posted by cache-monkey on September 13, 2004, at 22:36:08
I'm relatively new to the forum, and have been suffering from depression/anxiety. For me this is pretty related to my sleep. The worse I'm feeling that later I go to bed and the later I wake up. I realize that the sleep schedule's probably a function of my depression, but it's also making things worse. Basically, I get as much daylight during the middle of the summer that most 'normal' sleepers get in the winter time. And that's a low enough amount of daylight to make non-depressive people feel blue. I also tend to feel worse on cloudy days...
So, basically, part of my depression is probably related to Seasonal Affective Disorder (SAD), but year-round. I was talking to my p-doc about this and he suggested light therapy, which has been proven to be clinically effective for treating SAD. He noted that it's possible to buy commerical light boxes, but they run around $250. They're sometimes covered by insurance, but not mine. He suggested rigging up something myself using a halogen flood bulb fitted in a worklight from a hardware store.
I'm pretty meticulous about stuff (which is probably a part of my bigger set of 'issues' -- or possibly the fact that I'm a geek at heart :). So I thought I'd try to refine the idea to better match what has been used in the clinical setting.
What I've come up ended up costing ~$52, but only because I had to buy a shelf to attach the lamps. If you already have a place for them, it'd be only ~$32. Full details below.Peace,
cache-monkeyDisclaimers: [i] I am neither a doctor nor an engineer; [ii] please be careful with the placement of the bulbs, since halogens can generate a lot of heat; [iii] do not directly into the bulbs for any extended period of time, as this may damage your eyes; [iv] as usual, while light therapy works for many people, individual results will vary
Hardware:
1) Two standard aluminum utlity clip-lamps from a hardware store.
2) Two 75 watt Sylvania "Daylight Plus" PAR38 halogen flood lights. (The "DP" bulbs generate a whiter light... clinical studies of light therapy for SAD have found that full-spectrum light isn't essential, but it's nicer to have a whiter light.)Placement:
They need to shine directly on your face. The important thing is that your eyes are registering the light. But you really don't want them directly in your line-of-sight since this is a) annoying if not painful and b) probably not good for your eye-health. (See disclaimer [iii].) In any case, I clipped mine to a bookshelf that I put on my desk so that they're shining on my face from above.Exposure time:
As far as the time of exposure, this is going to depend on their distance to your face. Based on what I know of the studies that have been done on bright light therapy, and the product information on the Sylvania website, I came up with the following average times to get the clinically-studied therapeutic exposure, based on distance from face:
2.5' 31 mins
2.75' 38 mins
3' 45 mins
3.25' 53 mins
3.5' 61 mins
3.75 70 mins
4 79 mins
(These are just my estimates... See disclaimer [i].) Any closer than 2.5 feet and it's probably not safe due to the heat. I also don't give number above 4, since I don't think anyone wants to spend hours under the lights. If you want to have the lights at a greater/nearer distance you can figure out the exposure time based on the technical details provided below.Time of Day:
Depends on your sleep schedule. They generally recommend doing it all at once at your sleepiest time of day. I have delayed phase syndrome (late to bed, late to rise), for which they recommend doing it first thing in the "morning." People who get tired in the evening might want to try it then. (Oh, and for delayed phase people who get tired in the late afternoon, they also recommend a brief 5 minute session then.)Cost:
Bulbs- ~$15.50
Lamps- ~$16.50
---------------
Total- ~$32.00 + shelf for mounting lamps if neededTechnical details:
This does get technical, so you can probably stop reading here if you're not interested.The absolute brightness of a light is measured in lumens, but the effective brightness depends on how much area those lumens are spread out on. Lux is the metric standard measure of this (in units of lumens/square meter) and footcandles is the Englisgh measure (in lumens/square foot).
Basically, all of the clinical studies on light therapy for SAD have focussed on 10,000 L over half and hour, or 5,000 lux for an hour. So, to match the therapetuic set-up you need 300,000 lux-minutes (LM).
On the Sylvania website, you can get product information on their lightbulbs. For the "DP" series, this gives footcandles at distances of 3,4,5,6 and 7 feet from the bulb. Converting from footcandles to lux, and multiplying by 2 (because there are two lamps in the array) gives the number of of total lux (L) at each distance (D) from the lamp. Dividing 300,000 LM by L at each D gives the number of minutes of exposure (M) needed.
Since it's hard to get the light at exactly on of those distances, I decided to interpolate/extrapolate based on the numbers obtained from the product information sheet. When I graphed M against D for the distances included in the product information, it followed a smooth slight curve. So I figured that a quadratic approximation would be fine. Regressing M on D and D^2 yielded an R-squared of 0.99999, so I think its a good fit. Anyway, based on the coefficients from that regression, I put in various values of D to get the estimated minutes of exposure required:
Mhat = 2.58 + -1.19*D + 5.10*D^2
This is what the exposure time estimates presented above are based on.Note that the minutes of expopsure to get 10kL are interpolated for 3<D<4 greater and extrapolated (out of sample) for D<3. The extrapolated numbers might be a little bit less reliable. Also, the Sylvania product info notes that the numbers given are not specifications or standards per se, and that "Actual results may vary." So, there's proabably variation between bulbs in output of lumens, which means that these estimates are for the "average" bulb array. You could probably get a light meter if you want to do things exactly... But, as with all treatment effect studies, there's nothing magical about gettin exactly 10,000 lux over an hour. It's just the number they were working with. A little variation around that shouldn't throw things off too much, IMO. (But, again, see dislaimer [i].)
poster:cache-monkey
thread:390523
URL: http://www.dr-bob.org/babble/20040909/msgs/390523.html