Research on light therapy shows that it is effective for different kinds of depression. For example, a 2016 meta-analysis of nine varied clinical trials of nonseasonal depression concluded that the treatment significantly reduced symptoms.
A study by psychiatrist Ray Lam and his colleagues, published around the same time in JAMA, reached similar conclusions. This head-to-head comparison of light therapy with an antidepressant, fluoxetine (Prozac), and two control groups, found light therapy had an effect size of .8. This is officially considered large. In contrast, fluoxetine had a small effect size of .2, which did not differ statistically from placebo. Together, light therapy and fluoxetine had an effect size of 1.1. (See the bar graph below.)
Clearly, in this carefully-designed, multi-site study, light therapy was the winner by a large margin. So why didn’t psychiatrists grab their prescription pads and start recommending light therapy for patients who were depressed?
The Pill Paradigm
We live in a culture where taking pills is second nature. According to a recent study in JAMA, 15% of a nationally representative sample of the US population uses five or more prescription drugs. Further, the use of these drugs is increasing even when age is taken into account.
We asked some psychiatrists whether they thought light therapy might someday replace this reliance on pills. They were skeptical. Psychiatrists don’t change unless everybody else is doing it, they said.
“What if a celebrity, like Queen Elizabeth, were doing light therapy?” we asked.
A British psychiatrist laughed. “Queen Elizabeth,” he said. “That would work.”
Without Queen Elizabeth, however, it seems that a paradigm shift is not in our immediate future. As Thomas Kuhn, probably the world’s most influential philosopher of science, noted, major advances in science do not occur because practitioners are persuaded another view is correct. Rather, they take place because the proponents of the old view die out, and the adherents of the new paradigm take over.
Lost in Translation
With medicine, there is another stumbling block to progress, and it has to do with the funding sources for the public, medical schools, residencies, and beyond. In almost all states, physicians must take continuing medical education (CME) programs to maintain their licenses. These programs are often funded by pharmaceutical companies.
In theory, the pharmaceutical companies do not influence the content of the programs they fund; they just pay continuing medical education companies to produce material. However, many experts believe that such an ideal relationship does not exist in practice, and he who pays the piper calls the tune.
Let’s look at what this means for light therapy, which is not championed by pharmaceutical companies because it is a competitor.
From Conference to Clinic: What’s New in [Major Depressive Disorder] in 2015 discusses the study by Lam and colleagues that we describe above. The educational program, funded by pharmaceutical giants Takeda and Lundbeck, is free. You can access it at Medscape when you click on the link above if you register as a Medscape member–a quick and painless procedure.
However, nowhere in the discussion do the two presenters say that light therapy beat the antidepressant hands-down. This is rather strange, since in a head-to-head comparison, you would expect to find out which treatment did better. Leaving out that information is like describing a race, but not saying who won.
Instead, the slide says light monotherapy is superior to placebo. This is damning light monotherapy with faint praise; light monotherapy was superior not just to placebo, but to fluoxetine, the active comparator, and by a large margin!
Perhaps the effectiveness of light therapy was minimized because of the next subject: vortioxetine (Trintellix), an antidepressant from Takeda and Lundberg. The presenters, who have multiple financial ties to Takeda or Lundbeck, or both, state that vortioxetine is “fascinating,” and has a “robust” effect size of .5 for its effect on cognition.
An Uphill Battle
A culture of pills, backed by the power of Big Pharma.
While treatments derived from circadian rhythms are impressive, our pill culture, and the power of pharmaceutical companies, support the status quo. Unfortunately, this means that it will be a long time before physicians, and patients with depression, can see the light.