How Bright Light Therapy Helps with Low Mood, Sleep Problems and Jet Lag
By Daniel F. Kripke, M.D.
Last Revised April 2013
Bright Light for Depression: The Scientific Evidence
Bright light treatment for winter depression has been supported by dozens of studies demonstrating beneficial results (though there have been a few studies with unsuccessful results). The Clinical Practice Guidelines issued by the U.S. Department of Health and Human Services recognize bright light as a generally accepted treatment for winter depression.
Regarding the more-common non-seasonal depression, a formal Cochrane Collaboration meta-analysis showed that bright light is effective for non-seasonal depression. Cochrane reviews are the international gold standard for evaluating the clinical evidence for various treatments. In an abstract, Tuunainen expanded this analysis. A formal American Psychiatric Association Review found that bright light was effective for SAD but questioned the value for non-seasonal depression. However, the Psychiatric Association authors later admitted that they had made an error in computing their meta-analysis, so the benefit was greater than they had concluded. A more recent French review concluded that bright light therapy was useful for nonseasonal depression, at least combined with antidepressant drugs.
Recent studies emphasize the usefulness of bright light in treating depressed elderly individuals in the home and in treating pregnant and postpartum women with depression. Interest has been renewed in “chronotherapeutics,” a combination of morning bright light treatment with wake therapy, sometimes combined with moving the sleep interval a bit earlier as well. As yet, we do not have adequate randomized comparisons of the effectiveness of combined chronotherapy versus morning light treatment by itself, but the combined benefits appear relatively large
5.A. Is bright light only good in winter?
The earliest controlled report of bright light treatment for seasonal affective disorder (SAD) described remarkable 52% net benefits within one week; however, the bright light–treated patients were given high expectations which were not matched in the placebo-treated group. Patients with high expectations often report improvement through the power of positive thinking, but benefits of positive thinking need to be separated scientifically from the effects of bright light. Later and larger studies of SAD treatment have indicated that bright light may not be dramatically more useful than antidepressant drugs, and it is not clear whether SAD patients respond better to bright light than other people with depression.
Even if we were sure that SAD patients responded better to light than other depressed patients, it would often hard to tell what type of depression a person has. Follow-up of SAD patients by Dr. Rosenthal’s research group showed that the majority of patients first defined as SAD eventually displayed summer symptoms, if their illnesses continued to recur, and many needed antidepressant drugs. Over follow-up, such patients may be perceived as nonseasonal according to accepted criteria. Many SAD patients eventually require both bright light treatment and antidepressant medications outside the winter months. Because of controversial criteria and complex clinical course, it may often be impossible to define whether a depressed patient does or does not have SAD, so restricting light therapy to SAD would not be practical.
Even when seasonal pattern can be distinguished, there is no assurance that light treatment will work better than in nonseasonal patients, nor does seasonality exclude the usefulness of antidepressant medication in addition to bright light.
In conclusion, in my opinion, bright light is useful for people who are depressed, whether or not we think that they have SAD or winter depression. It is likely that for both nonseasonal and SAD patients, a combination of bright light, antidepressant drugs, and wake therapy is advisable.
5.B. More perspective on antidepressant medication
To have perspective on the results of bright light treatment, it is useful to understand the benefits which result from antidepressant drugs. Hundreds or perhaps thousands of controlled trials of antidepressant medications have been reported, with a great preponderance of evidence that medicated patients improve somewhat faster than comparison patients given placebo. Placebo means an inactive, dummy treatment. Nevertheless, many physicians suppose that the benefits of antidepressant drugs are greater than such trials actually demonstrate.
Because antidepressant medications may require six to 16 weeks to achieve substantial benefit, patients given placebo (dummy pills) for the same interval often display spontaneous remission. They get better by themselves, perhaps helped by hope and by encouragement from the researchers. The alleviation of symptoms attained during antidepressant drug treatment in most studies is due more to this spontaneous remission than to medication benefits. The benefits of antidepressant drugs are only clearly understood when the percentage remission of symptoms achieved with placebo is subtracted from the remission accompanying medication.
Only recently have overall and unbiased assessments of antidepressant drug effects become available. A compendium of antidepressant drug trials in thousands of patients reported to the U.S. Food and Drug Administration provided a general summary of antidepressant drug effects. The advantage of this report over previous compendia was the inclusion of rather unsuccessful studies which the pharmaceutical manufacturers were obliged to report, though they may not have wished to see such results published. In these studies, the eight-week net benefit of antidepressant drugs on the Hamilton Depression Rating Scale was only 8–12% better than the result with placebo. Another analysis of some of the same data found that the placebo groups had improved 58% percent at the last measurement and the drug-treated groups had improved 69%, a drug-related benefit of only 11%. An analysis of fluoxetine results reached similar estimates, even though some of the authors were employees of the makers of Prozac. Incidentally, this analysis found only seven clinical trials comparing fluoxetine to placebo, whereas we have at least 15 comparing bright light to placebo in nonseasonal depression. A comprehensive meta-analysis using response criteria obtained rather similar results and also demonstrated that there has been a bias to publish more successful results and to leave less successful results unpublished. Although these meta-analyses certainly demonstrate that antidepressant drugs have significant benefits for nonseasonal depression, the size of the antidepressant net benefit after eight weeks or more (approximately 8 to 19%) certainly does not appear superior to the one-week benefit of bright light treatment (approximately 12 to 35%). Moreover, very recent analyses have argued that antidepressant benefits are most impressive with the most severe depressions (often requiring hospitalization), whereas with relatively mild depressions, the benefits may be small or absent 
Incidentally, when antidepressant drugs fail to work well, addition of lithium treatment may be helpful. Also (particularly for young women), addition of thyroid hormone (T3 or triiodothyronine) may be helpful.
It is not wise to emphasize comparison of antidepressant drug benefits with bright light benefits, because there have been no direct randomizing comparisons of the two treatment approaches. Although the benefits of bright light might be greater and are almost certainly more rapid than benefits of medication, much more is known about the long-term benefits of antidepressant drug treatment, which has been much more extensively studied. Moreover, there really is no reason to inquire whether one treatment of depression is better than the other. The important point is that bright light and antidepressant drugs are best used in combination, probably also combining at least a half-night of wake therapy.
Endnotes for Chapter 5
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56. Bech, P et al. Meta-analysis of randomised controlled trials of fluoxetine v. placebo and tricyclic antidepressants in the short-term treatment of major depression. Brit.J.Psychiat. 2000;176:421-428. [return]
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