Just as seasonal and non-seasonal depression can be treated with light therapy, mania and hypomania can be treated with darkness. This symmetry was not immediately apparent when light therapy was first demonstrated in the early 1980s. Twenty years later, two case studies (1,2) and one open label clinical trial demonstrated that as little as three extended nights of bedrest in 10-14 hours of darkness could subdue a manic episode.
With the discovery in 2000 of blue-sensitive melanopsin-based photoreceptors in the retina — which mediate various non-visual effects of light including pupil constriction, melatonin suppression, and increased alertness — the question arose how this particular part of the light spectrum might also have psychoactive clinical effects.
As with bright broad-spectrum white light 25 years earlier, attention first focused on the winter depression of seasonal affective disorder, using “blue-enriched” vs “blue-free” light therapy devices to determine whether the short-wavelength region of the visible spectrum shows heightened antidepressant potency. Standard broad-spectrum light therapy lamps are also effective, of course, but the blue vs blue-free comparison heightens the contrast between active and placebo conditions. CET authors Dan Oren and Manuel Spitschan further explain how the components of light contribute to the antidepressant response.
On the other hand, blue blocking glasses have been found to be helpful for patients with mania. There have been three case studies and two clinical trials, the most ambitious in a placebo-controlled trial by Tone Henriksen and colleagues, which compared blue-blockers and clear glasses (as a placebo). The glasses were usually worn for 14 hours starting in early evening. The benefit of blue-blockers was a strong advantage in reducing manic symptoms. Importantly, side effects were negligible.
While this initial work is promising, we need more research on both the efficacy and tolerability of blue blockers. The glasses have been well accepted by hospitalized patients, even those with psychotic symptoms. Home treatment is more likely for patients with hypomania, where there is no staff to monitor compliance, just like for bright light therapy as home treatment. The results may be more variable, since patients with hypomania sometimes don’t want to see it end.
Care is needed when selecting blue-blockers for purchase. While they all have an orange or amber color, one needs to be sure that they cut off light wavelengths below approximately 540 nanometers, including invisible ultraviolet radiation (UV) that is potentially dangerous to the eyes. Drugstores and sports shops that market blue blockers for controlling visual glare are very unlikely to specify whether their products completely control melanopsin stimulation, which may be critical for the antimanic effect. CET recommends a vetted line of protective eyewear.
Blue blockers have many potential uses beyond their clinical indications. One study demonstrated that blue blocking glasses minimize the alerting effects of evening LED screen exposure from smartphones and computer screens. Other applications are improved adaptation to night shift work and to improved sleep in athletes to achieve higher peak performance.
CET Board members Anna Wirz-Justice and Michael Terman have described dark therapy as “an inexpensive adjuvant treatment which is free of side effects — and almost absurdly simple to administer . . . a splendid example of translational psychiatry, a neuroscience-based therapy.” What an unexpected opportunity for manic and hypomanic patients — not to mention those around them — to have such a simple addition to conventional anti-manic pharmacotherapy!
Konstantin V. Danilenko MD, Institute of Neurosciences and Medicine, Novosibirsk, Russia, is a biomedical researcher focusing on light physiology in humans. He has conducted a series of basic and clinical studies on biological rhythms, melatonin, winter depression, and reproductive function. He serves on CET’s Board of Advisors and is a long-time member of the Society for Light Treatment and Biological Rhythms.