“Dark Therapy”, in which complete darkness is used as a mood stabilizer in bipolar disorder, roughly the converse of light therapy for depression, has support in several preliminary studies.
Although data are limited, darkness itself appears to organize and stabilize circadian rhythms. Yet insuring complete darkness from 6 p.m. to 8 a.m. the following morning, as used in several studies thus far, is highly impractical and not accepted by patients. However, recent data on the physiology of human circadian rhythm suggests that “virtual darkness” may be achievable by blocking blue wavelengths oflight.
A recently discovered retinal photoreceptor, whose fibers connect only to the biological clock region of the hypothalamus, has been shown to respond only to a narrow band of wavelengths around 450 nm. Amber-tinted safety glasses, which block transmission of these wavelengths, have already been shown to preserve normal nocturnal melatonin levels in a light environment which otherwise completely suppresses melatonin production.
Therefore it may be possible to influence human circadian rhythms by using these lenses at night to blunt the impact of electrical light particularly the blue light of ubiquitous television screens, by creating a “virtual darkness”.
One way to investigate this would be to provide the lenses to patients with severe sleep disturbance of probable circadian origin. A preliminary case series herein demonstrates that some patients with bipolar disorder experience reduced sleep-onset latency with this approach, suggesting a circadian effect.
If amber lenses can effectively simulate darkness, a broad range of conditions might respond to this inexpensive therapeutic tool: common forms of insomnia; sleep deprivation in nursing mothers; circadian rhythm disruption in shift workers; and perhaps even rapid cycling bipolar disorder, a difficult- to -treat variation of a common illness.
A series of patients were given amber-tinted plastic safety glasses in the context of outpatient treatment for Bipolar Disorder. Those selected for this trial had initial insomnia at minimum; many had an additional evidence of circadian rhythm disruption, such as highly fragmented sleep.
Consecutive outpatients with a clinical diagnosis of Bipolar Disorder by DSM-IV [21] criteria (5% Bipolar I, 43 % Bipolar II, 52% BP NOS) were offered a trial of this approach. Given the simplicity of the intervention and the private outpatient setting, Institutional Review Board approval was not sought. Exclusion criteria included ongoing substance use, personality disorder as a primary diagnosis, and inability to understand the rationale behind the intervention. All patients continued their prior pharmacotherapy.
Amber-tinted lenses of the same design used in the study of melatonin preservation [18] were obtained from a light research team at John Carroll University (www.lowbluelights.com). A fit-over design allowed use of regular glasses if needed. Patients were instructed to begin use of the lenses around 8 p.m., removing them at bedtime after all artificial lighting was extinguished.
One of the most striking findings was patients’ willingness to try this approach once they understood the background research. None refused, suggesting that treatment using restoration of a more “natural” light environment has strong appeal. Although 0.5 mg of melatonin at dusk likely has the same biological effect and might be preferred by many patients (Alfred Lewy, personal communication, 2006), clearly the amber lenses are easily accepted; most patients were eager to try them.
This is an extract from James Phelps paper, Dark therapy for bipolar disorder using amber lenses for blue light blockade. Full reference: Phelps, J. (2008). Dark therapy for bipolar disorder using amber lenses for blue light blockade.’ Medical Hypothesis. 70, (2), p224-249.