Dark therapy
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- This article is about the medical uses for the absence of light. For alternative uses see Darkness (disambiguation).
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 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. (Page 223)
- [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. (Page 226)
Clinical pharmacology
Researchers hypothesize that benefits of being in the dark are due to melatonin production by the pineal gland, which occurs when the eyes are deprived of light,[1][2] as shown during controlled light-dark cycles, even for some blind subjects, indicating that melanopsin is responsible for circadian entrainment in humans.[3]
Bipolar disorder treatment
A single small scale study done in Hospital San Raffaele of Milan, Italy, concluded that chronobiological interventions and control of environmental stimuli can be a useful add-on for the treatment of acute mania in a hospital setting. [4] Further examinations were done on single patients, and are reported on the link regarding 24hr biological clocks [5]. A study regarding 48 hour cycles has also been reported [6]
Other conditions
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.[7]
Melatonin secreted is preventative in cancer, and supportive of bone metabolism, immune function and detoxification.[8]Melatonin has also been cited to reduce hypertension, produce better sleep for those with insomnia, and acts as an antioxidant.[9]
Virtual darkness
By using amber lenses, researchers were able to block blue spectrum light, which affected "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". PMID 17637502
Side effects
No side effects have been officially reported for dark therapy.
Treatment constraints
When having dark hours at home or in hospital, patients will often be exposed to fewer light hours than in their usual environment, 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.
References
- Dark therapy for bipolar disorder using amber lenses for blue light blockade. PMID 17637502
- Wirz-Justice, Anna. Chronobiological strategies for unmet needs in the treatment of depression. MEDICOGRAPHIA, VOL 27, No. 3, 2005 p. 223-227 [10]
- Human circadian rhythms: physiological and therapeutic relevance of light and melatonin. PMID: 17022876
- Human pineal physiology and functional significance of melatonin. PMID: 15589268
- Light-dark cycle synchronization of circadian rhythm in blind primates. Journal of Circadian Rhythms 2005, 3:10 (6 September 2005)
- Dark therapy for mania: a pilot study. Bipolar Disord. 2005 Feb;7(1):98-101. PMID: 15654938
- Neurobiological Findings Before and During Lithium of a Bipolar Patient with Rapid Cycling PMID: 11893872
- Magnesium depletion with hypo- or hyper- function of the biological clock may be involved in chronopathological forms of asthma. PMID: 15945613
- Therapeutic treatments potentially mediated by melatonin receptors: potential clinical uses in the prevention of osteoporosis, cancer and as an adjuvant therapy. PMID: 17014686
- Human pineal physiology and functional significance of melatonin. PMID: 15589268