Light therapy appears to be efficacious for seasonal affective disorder
(SAD) and for nonseasonal depression, according to a meta-analysis of
randomized controlled trials.
The analysis was reported in the April American Journal of
Psychiatry. The lead author was Robert N. Golden, M.D., who led a work
group charged by APA's Council on Research and Committee on Research on
Psychiatric Treatments to use the principles of evidence-based medicine to
examine the efficacy of light therapy.
Golden and colleagues found that many of the studies in the literature on
light therapy did not meet selection criteria for the meta-analysis,
reflecting methodological problems inherent in the study of light. Prominent
among these is the difficulty of defining parameters of active versus placebo
"There is an unavoidable challenge in setting up a placebo condition
that subjects cannot distinguish from active treatment, although this usually
applies to pharmacotherapy research as well, whenever active treatments have
side effects and placebos do not," Golden told Psychiatric
Small sample size also characterized some studies that did not meet
criteria, reflecting the lack of industry support for research on light,
But those studies that did meet selection criteria for the meta-analysis
demonstrated a significant reduction in depression symptom severity following
bright light therapy in SAD and in nonseasonal depression. The analysis also
showed a significant effect with "dawn simulation" in SAD. (Dawn
simulation uses a light that comes on very slowly in the early morning, to
imitate a natural sunrise. Standard light therapy typically makes use of a
light box that provides persistent bright light.)
"When the `noise' from unreliable studies is removed, the effects of
light therapy are comparable to those found in many antidepressant
pharmacotherapy trials," Golden and colleagues wrote.
They systematically searched PubMed for articles published between January
1975 and July 2003 on light therapy for mood disorders. Included studies were
required to be randomized, controlled trials of patients in the acute phase of
treatment and to have a credible placebo-control condition.
For bright light treatment of SAD, minimum treatment dose was defined as
four days of at least 3,000 lux-hours (for instance, 1,500 lux for two hours
or 3,000 lux for one hour). Placebo comparison groups were required to receive
a maximum of 300 lux.
For dawn-simulation studies, active intervention was required to consist of
increasing light exposure from 0 lux to 200-300 lux over one hour to 2.5
hours, and the placebo condition had to consist of an increase that was less
than 5 lux and/or less than 15 minutes in duration.
Golden and colleagues found that only 23 of 173 studies (13 percent) met
the selection criteria. But those 23 studies showed a significant reduction in
depression symptom severity associated with bright-light treatment and dawn
simulation in SAD.
Significant reduction in symptoms was also demonstrated with bright-light
treatment in nonseasonal depression. Bright light as an adjunct to
pharmacotherapy was not found effective, according to the report.
Norman Rosenthal, M.D., a psychiatrist who pioneered SAD research and
treatment using light therapy, told Psychiatric News that the
findings confirm that light is extremely effective in the treatment of
patients with mood disorders and should help to push the treatment into the
mainstream. He emphasized the finding that effect sizes for light therapy were
comparable to those found for antidepressant medication.
He underscored the finding that light therapy was also found effective for
nonseasonal depression. "I don't think if you asked 100 psychiatrists
that even 5 percent would have endorsed that," he said. "So it's a
very interesting finding."
He added that the finding should not be surprising given that light is
known to impact fundamental neurotransmitter systems.
Rosenthal is a clinical professor of psychiatry at Georgetown University
School of Medicine and author of Winter Blues. (The book was
originally published in 1989 under the title Seasons of the Mind; it
was republished under the new title in 1993, and a second edition was
published by the Guilford Press in 1998. The third edition is due out this
Rosenthal believes the finding that light was not effective as an adjunct
to pharmacotherapy is an artifact of the small number of studies that have
been conducted on the subject.
It would be "extraordinary" for an antidepressant that is
effective "in its own right not to be effective as an adjunct to
something else," he said. "That would be almost unprecedented, and
my guess is that this is because the quantity of data is
Rosenthal said that research on light therapy today has come to a virtual
standstill because of a lack of funding, and thus the therapy has been
marginalized. Federal funding that had once been generous has dried up, and
since equipment used for light therapy does not hold the promise of yielding
huge profits for manufacturers, other sources of funding have not
"There is no money in light, and nobody has a lot to gain from it
economically," he said.
The study, "The Efficacy of Light Therapy in the Treatment of
Mood Disorders: A Review and Meta-Analysis of the Evidence," is posted
Am J Psychiatry2005162656