Light therapy in an experimental subject

Leslie Lammie in the New York Times

By now the question is settled. Light therapy for depression and delayed sleep phase can achieve remarkable improvement. In speed of action and ultimate outcome, it can beat antidepressants and sleeping pills. But where some see progress, others see potential profits … big and fast profits. What could be easier? The technology is elementary, it is easy to come up with design variations that look unique (or at least special), low-cost production overseas is by now standard, Amazon is there to provide an inexpensive combo of advertising and sales… Best of all, there is virtually no oversight by federal regulatory agencies such as the FDA and Federal Trade Commission. Prices keep falling, but sell enough units and your profits are safe. And many consumers are understandably curious to try any new cool-looking gadget that might give them symptomatic relief without the burden of medical expenses.


Does light therapy work? The basis for saying it does dates back to ambitious controlled clinical trials sponsored by the National Institute of Mental Health in the 1980s and 1990s. The work began at major university research centers – and within the NIMH itself – right after the initial pilot study was presented at a psychiatry meeting. An international network quickly formed among researchers excited by this breakthrough. Their goal was to replicate and expand on the initial finding, using a standardized protocol to permit comparison of outcomes. To achieve this, they agreed to:

  • use systematic psychiatric screening for seasonal affective disorder (SAD) in research volunteers (who were unpaid, to reduce bias)
  • review medical and psychiatric history to restrict the study to healthy patients without multiple psychiatric issues
  • measure symptom severity during the depressive episode, before treatment began
  • administer broad-field, large-screen, bright white light from specially constructed light boxes
  • independently give comparison treatments (dim light, colored light, different times of day of treatment sessions, non-light treatment) to determine if bright light did best
  • monitor depressive symptoms weekly, with interviewers who were kept unaware of the treatment assignments and who used a set of common questions to ensure generalizability
  • continue monitoring after the treatment period ended, to document the rate of relapse
  • compare patients’ expectation ratings for improvement with their actual improvement (another way of measuring possible placebo effects)
  • and, when funds permitted, measure physiological changes before and after light therapy (especially the timing of melatonin production by the pineal gland, which is a basic index of circadian rhythm)

All told, hundreds of patients volunteered for these trials. Taken together, the results made a very promising case that light therapy is both safe and effective. The cost of these clinical trials (none of which had industry sponsorship)?  Tens of millions of dollars.  The potential benefit?  Relief for tens of millions of patients with seasonal depression (and, as  we now know, nonseasonal depression too).  Not a bad payoff…


Once news of the positive research results started to spread beyond the little circle of researchers, many entrepreneurs spotted an opening for commercial exploitation. Well more than a dozen companies started manufacturing and selling light therapy devices. Their motives may have been impeccable, but their situation created a large problem. To be competitive, each had to offer something to distinguish their product from others. One way was to make it less expensive. And one obvious way to do that was to skip costly controlled clinical trials. Manufacturers of antidepressants and sleeping pills are legally and ethically required to conduct such tests, but a light box is not considered a medication and is free of such requirements.

Companies rationalize this lapse in various ways. For one, by not making explicit medical claims for their novel, untested devices: “Lighten your blues (we’re not treating your disorder),” etc., etc.  For another, by trumpeting consumer testimonials (was there ever a product that didn’t have at least a few satisfied users?).  And still another, by engaging a clinician to try out the device on a few patients and rate their improvement. Needless to say, this is very far from meeting the standards of a controlled clinical trial, and is rife with placebo potential.

Notice, too, that it is practically impossible to say that these devices are ineffective. That, too, would require a real clinical trial. So even those that may be totally useless can stay on the market as long as the maker can find ways to convince people to buy them.

So here we are. Given this situation, what should you — or anyone who thinks light therapy might help them — do? Our advice is straightforward: Go for a device that has undergone kosher clinical testing. In our book, Chronotherapy, we discuss the criteria you should use in selecting one. And in our next blog post, we will raise some of the specific concerns to keep in mind.

About the Authors

Ian McMahan, Ph.D.

Ian McMahan, Ph.D., is a Professor Emeritus of Psychology at Brooklyn College, CUNY, and a lifelong writer.

Michael Terman, Ph.D.

Michael Terman, Ph.D., is a professor of clinical psychology in psychiatry at Columbia University.

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