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Should light therapy be recommended for depression in general — not just in winter?

Light therapy effective for treating depression, not just winter blues

Our Review Summary

light therapyThis brief story gives a tantalizing glimpse into a small study of 122 people with major depression, but it leaves us wanting a bit more.

The randomized controlled study divided patients into groups with some receiving light therapy alone, some receiving light and antidepressant, and others received sham therapies imitating light and placebo medication. The most improvement was seen in the groups receiving light alone or light-plus-antidepressant. Paraphrasing the researchers, the story concludes that “enough clinical evidence now supports mental health professionals recommending light therapy as a treatment for depression.” But the story never really backs up that statement. It doesn’t make the case for why this one rather small study puts the evidence squarely beyond doubt. Nor does it delve very deeply into the study’s limitations.

We would have welcomed more metrics and a clearer explanation for how this one study could change practice going forward.


Why This Matters

Major depression is the second-ranked cause of disability in the world, and estimates say it strikes 1 in 20 people in the United States. If light therapy, which is relatively low-cost, could improve the treatment of major depression it would help millions. It might also be an economic boon by helping relieve the lost wages and crippling disability of those who remain diminished for years.


Does the story adequately discuss the costs of the intervention?


The story squeaks by on this with mention that light therapy is “cheap” and easy to use. We would have preferred some numbers giving prices for the light sources that patients typically use at home and some estimate for a therapeutic course of psychotherapy (which is often provided in combination with light therapy).

Does the story adequately quantify the benefits of the treatment/test/product/procedure?

Not Satisfactory

The only attempt to describe benefits is vague.

Here it is, with italics by editors:

“Although the light therapy helped many patients, it provided the most benefit to those who were also taking the antidepressant. About 60 percent of those using light therapy with the antidepressant reported feeling almost back to normal, Lam said.”

Quantifying means we’d like to know some metric or measure that researchers used to compare the different groups of patients. In the original journal article, the authors said they used MADRS (Montgomery-Asberg Depression Rating Scale) changes from baseline to 8 weeks into the different therapies. It would be useful to know where they started on that scale and where they ended up — and whether that difference was meaningful.

Does the story adequately explain/quantify the harms of the intervention?

Not Satisfactory

The short story does not mention potential harms of light therapy., and it doesn’t say there are few or none known. Either way, we would have liked the story to address the notion of harm I [Editor’s note: As pointed out by a commenter, the story does note that light therapy “comes with few side effects compared to medication such as antidepressants.” That’s more than we gave the story credit for initially, but we decided to keep the Not Satisfactory rating because the story does not say what any of those side effects are or how frequently they occur.]

Interestingly, if you look at the table on adverse effects in the original study, it shows that close to 1/4 of those on light therapy experienced diarrhea. We can’t exactly explain that strange finding but it was worth mentioning.

Does the story seem to grasp the quality of the evidence?

Not Satisfactory

The story establishes this was double-blind randomized controlled study with a high quality of evidence. But it doesn’t comment on the fact that there were only 122 participants and that this was not a large sample. The small size of the study is puzzling since the study used three centers over five-plus years. It also was conducted in Canada, which has shorter days in the winter and long ones in the summer compared with the U.S. The relation of the treatments to these cycles was not discussed. In short, there were a number of questions about this study that could have received more thorough attention, but the story didn’t address any limitations and was unwaveringly positive in its description. Especially for a U.S. audience, it would be important to see this study replicated at U.S. latitudes and in a larger study sample to say that light therapy is unquestionably effective for non-seasonal depression.

Does the story commit disease-mongering?


There was no disease mongering.

Does the story use independent sources and identify conflicts of interest?


The story included a quote from an independent source other than study authors, so we’ll award a Satisfactory. However, it would not have taken much to find someone who would have raised some questions about the study and offered a note of caution or two.

Does the story compare the new approach with existing alternatives?


Even in a short word count, this story did convey that there are alternatives, including antidepressants and psychotherapy.

Does the story establish the availability of the treatment/test/product/procedure?

Not Applicable

Since these lights probably aren’t very difficult to find, we’ll rate the story Not Applicable here. The story doesn’t specifically address availability and it could have noted what kind of light is needed and whether these lights are widely available. But we won’t ding the story for not mentioning this.

Does the story establish the true novelty of the approach?


The story does not say this was the first randomized trial about non-seasonal depression and refers to previous research. It does imply that this study reinforces a change in practice to include light therapy as another alternative. We wish the story had explained perhaps why this study could lead to a conclusive change in practice.

Does the story appear to rely solely or largely on a news release?


Because an independent source is quoted, we can be reasonably certain that this story went beyond any news release.

Total Score: 6 of 9 Satisfactory

Comments (2)

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Diane Heditsian

November 30, 2015 at 9:16 am

Although the story doesn’t say what the harms of light therapy may be, it DOES SAY, that the side effects are few: “Light therapy is cheap, easy to use and comes with few side effects compared to medication such as antidepressants, said lead author Raymond Lam, a professor of psychiatry at the University of British Columbia.”


    Kevin Lomangino

    November 30, 2015 at 12:45 pm


    Thanks for pointing this out. I have updated our comments under the “Harms” section of the review to reflect this information.

    Best regards,

    Kevin Lomangino
    Managing Editor