[added 2/2016]

This page provides details on one of the biggest and most sophisticated studies of light therapy so far.  The  study was conducted  by Raymond Lam and colleagues, across various regions of Canada.Lam



  • Light therapy outperformed fluoxetine/Prozac
  • Both together was better than light alone

Conclusion: for people who are interested in light therapy, and believe that it can help their depression, it is very effective, perhaps even better than an antidepressant. This is not just for Seasonal Affective Disorder, it’s for depression at any time of year.

But…the study had one big problem — fluoxetine alone was no better than placebo.  So is some doubt about whether the set-up was fair to the medication approach. To understand that, you’ll need to see the details.

Study Details

Here are the results (click on the graph to enlarge).  Scores going down reflect decreasing depression.  That’s placebo in green, fluoxetine in yellow, light therapy in red, and combination in brown.


Light Study Lam 2016


These are big reductions.  Combination treatment (brown) was clearly best of all.  Interestingly, fluoxetine barely beat placebo, and, as you’ll see below, in another way of looking at the results, it came in behind placebo.  So look more closely now at the placebos used.

Everyone in the study received a pill, and everyone in the study received a treatment device.   This is a little tricky;  try this guide:

Which Pill?
Fluoxetine Placebo

Light box

Group A:

light therapy

Group B:

light therapy
placebo pill

Inactive ion
Group C:

placebo device

Group D:

placebo pill
placebo device

Although this is an amazing advance compared to prior research on light boxes, there’s a problem with this design.  Participants were told that “half the treatment devices were inactive”, which was true: half were inactive ion generators! But all the light boxes were active, emitting light.  So essentially the light therapy was not “blinded” (no pun intended): the participants knew if they were getting active light therapy. And this is Canada: who there does not know that light therapy is regarded as a treatment for seasonal depression, i.e. an “antidepressant”?

Thus you see, this is not exactly a fair trial:  participants knew there was a 50% chance the pill they were taking was a placebo.  But if they were using a light box, there was almost certainty that they knew they were on an active treatment. These differences really matter: it’s like the light box had a huge head start on fluoxetine, because the pill had a 50/50 chance of  being a placebo, whereas the light box was rather obviously a working light box!.

That might partly explain why fluoxetine was not really better than placebo. Okay, in the above graph it was slightly better, but not much (the yellow line falls farther than the green one).  But  if you compare the number of people who reached “remission” ( they were so much better, they weren’t depressed anymore), then fluoxetine was clearly not better than placebo, maybe a bit worse:

placebo fluoxetine light therapy combination
Patients in remission 30% 20% 45% 60%


So now what? Is light therapy really effective for non-seasonal depression, or was this result a really good double-placebo response?  Well, one way to figure it: a 60% remission rate is almost unheard of in antidepressant studies. Even response rates (patients whose depression scores went down by half or more) are not usually that high.  Remission rate is usually more like 15-30%.  So, in a patient who is really set up to believe light therapy is going to help (as the subjects in this study very likely were), a light box alone is a very reasonable treatment approach.   Using a light box instead of a pill, like fluoxetine or some other antidepressant, is fully justified by this study.

But don’t forget that bipolar depression appears to be different, at least in terms of the timing and dose of light required. See that section of the Light Therapy page for cautions for people with bipolarity!