Daylight saving time ends on Sunday, November 1. About two weeks into the 5 p.m. sunsets, a lot of us will order a light therapy lamp, set it on the kitchen counter, and use it faithfully for a while. By January it’s propping up a stack of mail. I don’t blame willpower for that, and I rarely blame the lamp. The best long-term research on light therapy suggests it works well for winter depression, and that it tends to fail in the boring parts after unboxing: how far away the lamp sits, what time you switch it on, and if you’re still switching it on in February.
A light therapy lamp only hits 10,000 lux at one distance
Every lamp in this category sells the same number. The National Institute of Mental Health describes a 10,000 lux light box as roughly 20 times brighter than ordinary indoor light, used for about 30 to 45 minutes a day, usually first thing in the morning. The box rarely explains that lux measures the light landing on a particular spot. It says nothing fixed about the lamp itself. Move your face back a foot and the number on the box no longer describes what reaches your eyes.
Now compare the fine print with the medical advice. Mayo Clinic says to place a light box about 16 to 24 inches from your face. Carex rates its Day-Light Classic Plus ($169.99 on Carex’s own site) at 10,000 lux “at 12-14 inches.” Verilux’s popular HappyLight Luxe ($69.99) says it delivers “up to 10,000 Lux,” and its product page doesn’t list a distance at all. You have to open the manual to find out what “up to” is hiding.
The math on a lamp that sits a foot too far away
Here’s how the gap plays out at a real breakfast table. Light spreads as it travels, and the inverse square law gives a rough estimate: brightness falls with the square of the distance. Big flat panels fall off a little more gently than a bare bulb at close range, so read this as a ballpark figure.
Say you set the Carex at 20 inches, comfortably inside Mayo’s range, because that’s where the counter puts it. Its rating holds at about 13 inches. Thirteen divided by 20 is 0.65. Square that and you get roughly 0.42, so the 10,000 lux on the box becomes something like 4,200 lux at your eyes. The early studies paired 10,000 lux with 30 minutes, which researchers sometimes write as 300,000 lux-minutes. Getting the same total at 4,200 lux would take about 71 minutes, and nobody is sitting through that at 6:45 on a Tuesday.
Please don’t fix this by extending your sessions on your own. Fix it by moving the lamp. Find the distance in the manual, put a tape measure on the table once, and set it there. If the tested distance is so close that you’ll never use it, buy a bigger panel that holds its brightness farther out. For scale, the University of Vermont trial I’ll get to in a minute used a 23 by 15½ inch SunRay box, about the footprint of a carry-on suitcase. The HappyLight Luxe measures roughly 7.5 by 11.7 inches. Both get called a “SAD lamp,” but at 20 inches they’re not delivering the same thing.
When you use it matters more than which brand you buy
Mayo’s guidance is to use the box within the first hour after waking, for about 20 to 30 minutes, with your eyes open but not staring into the light. The morning timing has a reason behind it. NIMH notes that people with winter-pattern seasonal affective disorder tend to produce too much melatonin, the hormone that drives sleepiness, which is part of why the condition comes with oversleeping. (We covered how melatonin and other hormones shape your sleep in our guide to the sleep-hormone connection.) Bright light early in the day tells your internal clock it’s morning. The same lamp at 4 p.m. sends a different message.
So the lamp should live wherever your first hour already happens: beside the coffee maker, behind the laptop where you skim email, next to the bathroom mirror if that’s where you do your makeup. If you’ve read our piece on habit stacking, this is the same move. Attach the new habit to one you already do every morning without thinking.
The real failure point is February, and the research shows it
The study I keep coming back to is Kelly Rohan’s trial at the University of Vermont, published in the American Journal of Psychiatry in 2016. Researchers randomly assigned 177 adults with winter depression to six weeks of either light therapy or CBT-SAD, a version of cognitive behavioral therapy built for seasonal depression and run as twelve 90-minute group sessions. At the end of treatment the two groups were almost identical: 47.2% of the light therapy group and 47.6% of the CBT group were in remission.
The difference showed up later. Every September the team mailed reminders to the light therapy group and offered to lend them the same light box again. Even so, only 34.9% were still using light therapy the next winter, and 30.6% the winter after. In an earlier pilot, 2 out of 19 kept it up. By the second winter, 45.6% of the light therapy group had a recurrence, compared with 27.3% of the CBT group. The authors’ explanation is plain: light therapy suppresses symptoms while you use it, and it stops helping once the lamp goes back in the closet.
The top “best SAD lamp” roundups I read this week skip this entirely. They rank lamps by lux and glare, which is useful, but the trial says most people fall off at adherence, and you can put a price on that. Spread a $169.99 Carex over the roughly 150 mornings between mid-October and mid-March and it costs about $1.13 a morning in year one, or about 38 cents a morning over three winters. If you quit on December 1 after about 45 mornings, it comes to $3.78 a morning, and you’ve stopped right before the darkest weeks of the year. A $69.99 HappyLight you use every single morning is a better deal than either.
What the lamp can’t do, and who should check first
Seasonal affective disorder isn’t evenly distributed. A 1990 study in Psychiatry Research by Rosen and colleagues found rates of 1.4% in Sarasota, Florida, and 9.7% in Nashua, New Hampshire. NIMH also notes that SAD is much more common in women and usually starts in young adulthood. A formal diagnosis requires the seasonal pattern to show up for at least two consecutive years, and the symptoms go well past the winter blues: lasting low mood, losing interest in things you normally enjoy, oversleeping, carb cravings.
Before you plug anything in, know that Mayo Clinic points out that light boxes aren’t approved or regulated by the FDA for SAD, so look for one that’s made for SAD and filters out UV. (Lamps sold for skin conditions give off UV and can hurt your eyes.) If you have bipolar disorder, talk with your doctor before starting, because increasing light exposure too quickly can trigger manic symptoms. If you have glaucoma, cataracts, or eye damage from diabetes, check with your eye doctor first. If one winter with a lamp didn’t do enough, ask about CBT-SAD. The Vermont data suggests its benefits last longer.
So before you add a light therapy lamp to your cart this month, decide where it’s going to sit, measure that distance, and pick a lamp rated for it. Then set a calendar reminder for the first week of January asking whether you still use it. That reminder may end up doing more for you than the brightness rating. And if what you’re feeling is heavier than a winter slump, talk to your doctor. If you’re struggling, you can call or text 988 any time.