If light is an antidepressant (true) and antidepressants can make bipolar disorders worse (true), can darkness make bipolar disorders better? Might darkness be anti-manic?
This idea was explored over 2 decades ago, with a stunningly successful case report from the National Institute of Mental Health (NIMH) demonstrating that in at least 1 patient, darkness was indeed a mood stabilizer.1 But the protocol was arduous: 14 hours of enforced darkness every night.
It was so effective, they backed off to 10 hours, from 10 pm to 8 am, which kept the patient well with no medications for over a year. Yet, as clinicians know, patients still resist giving up their electric light, especially their TVs, tablets, and phones.
Hold that thought; and consider a completely separate line of research, which found that all wavelengths of light are not created equal. Blue light is by far the most powerful in setting circadian rhythm.
A new retinal photoreceptor, not a rod or cone, was discovered in 2001; it is sensitive primarily to blue light.2 These receptors connect not to the visual cortex but to the suprachiasmatic nucleus of the hypothalamus, wherein resides the primary biological clock. They are “circadian photoreceptors.”
Now put these 2 lines of research together. At night, when evolutionarily we should have 8 to 14 hours of darkness, one can create “virtual darkness” by blocking just the blue wavelengths of light. This can be done at the source (F.lux for Windows; NightShift for recent Apple products; and lowbluelights.com for no-blue bulbs and nightlights) or by simply donning a pair of amber-colored safety glasses.
The latter are available as fit-over-glasses, # S0360X; or a stylish version for young people with good eyes, # 3S1933X (purchase from Amazon—or, in a fun twist, from your local Airgas welding shop, ~$9). These safety glasses have been shown to preserve melatonin production at night even in a fully lit environment.3 About 50% of patients responded to wearing the amber lenses with reduced sleep latency and improved sleep quality.4
But now the acid test: if darkness is a mood stabilizer, and if amber lenses produce physiologic darkness, then can the lenses treat acute mania?
This has just been shown quite conclusively5 (to the extent that a single randomized trial is conclusive; but note this is a replication of another small inpatient study that used real darkness and found similar, though slightly less robust results6).
In the new study from Norway, patients being admitted with bipolar mania were randomized to wear amber lenses or control clear lenses whenever they were not in real darkness during the 14-hour period from 6 pm to 8 am.
Dr Phelps is Director of the Mood Disorders Program at Samaritan Mental Health in Corvallis, Ore. He is the Bipolar Disorder Section Editor for Psychiatric Times. Dr Phelps stopped accepting honoraria from pharmaceutical companies in 2008 but receives honoraria from McGraw-Hill and W.W. Norton & Co. for his books on bipolar disorders.
1. Wehr TA, Turner EH, Shimada JM, et al. Treatment of rapidly cycling bipolar patient by using extended bed rest and darkness to stabilize the timing and duration of sleep. Biol Psychiatry. 1998;43:822-828.
2. Brainard GC, Hanifin JP, Greeson JM, et al. Action spectrum for melatonin regulation in humans: evidence for a novel circadian photoreceptor. J Neurosci. 2001;21:6405-6412.
3. Kayumov L, Casper RF, Hawa RJ, et al. Blocking low-wavelength light prevents nocturnal melatonin suppression with no adverse effect on performance during simulated shift work. J Clin Endocrinol Metab. 2005;90:2755-2761.
4. Phelps J. Dark therapy for bipolar disorder using amber lenses for blue light blockade. Med Hypotheses. 2008;70:224-229.
5. Henriksen TE, Skrede S, Fasmer OB, et al. Blue-blocking glasses as additive treatment for mania: a randomized placebo-controlled trial. Bipolar Disord. 2016;18:221-232.
6. Barbini B, Benedetti F, Colombo C, et al. Dark therapy for mania: a pilot study. Bipolar Disord. 2005;7:98-101.