Dark Therapy

Sleep hygiene

Dark therapy is an experimental treatment which involves eliminating all light in the subject’s environment, for a period of six to sixteen hours per day, in combination with a regular sleep schedule. Dark therapy manipulates circadian rhythms acting on hormones and neurotransmitters. It has been proposed recently (2005) to combine the chronobiological manipulations of light/dark and/or sleep/wake therapies with psychopharmacological medication.

In the words of Swiss neuroscientist Anna Wirz-Justice: ‘Light therapy has undergone widespread controlled randomized clinical trials, and wake therapy has been so widely studied over decades that the efficacy data are strong. These nonpharmaceutical, biologically based therapies are not only powerful adjuvants, but also antidepressants in their own right… [P]ilot studies suggest that the simple measure of promoting long nights (more rest, more sleep, no light) can stop rapid cycling in bipolar patients, or diminish manic symptoms — intriguing findings that require replication.

Researchers hypothesize that benefits of being in the dark are due to melatonin (sleep hormone) production by the pineal gland, which occurs when the eyes are deprived of light, as shown during controlled light-dark cycles, even for some blind subjects, indicating that melanopsin (a retinal photopigment) is responsible for circadian entrainment in humans. Dark therapy has also been tried (in combination with bright light therapy, etc.) for other conditions where seasonal exacerbation of symptoms are notable, such as nocturnal asthma and associated depression, migraine, dyssomnia, chronic fatigue syndrome, and fibromyalgia. Melatonin is preventative in cancer, and supportive of bone metabolism, immune function and detoxification. It has also been cited to reduce hypertension, produce better sleep for those with insomnia, and acts as an antioxidant.

By using amber lenses, researchers were able to block blue spectrum light, which affected the ‘physiology of human circadian rhythm … suggesting a circadian effect.’ This effect was previously noted with ‘amber-tinted safety glasses’ which ‘preserve normal nocturnal melatonin levels in a light environment which otherwise completely suppresses melatonin production.’ No side effects have been officially reported for dark therapy. However, when having dark hours at home or in a hospital, patients will often be exposed to fewer light-hours than in their usual environment, thus requiring a ‘light tight’ environment. Light from most sources could disrupt dark therapy. Also, it is necessary to have dark therapy hours at specified times during each day.

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