Dark therapy is a branch of chronotherapeutics that uses the absolute absence of light to improve psychological health and re-adjust circadian rhythms, specifically the sleep-wake cycle. Functions of the human body naturally follow a 24-hour cyclical period that mirrors the sunrise-sunset pattern; when too much stimuli disturbs this rhythm, insomnia, depression, and mood swings can result. People with mania, schizophrenia, or bi-polar disorder are especially susceptible to skewed circadian rhythms and can have their conditions worsened by body clock disruptions. By blocking blue light, which is a potent, visible, short-wavelength light, dark therapy can restore the body to its natural rhythm, often within three days.
Giving the sky its characteristic blue hue, blue light radiates in wavelengths that reach 468 nm. This light, more than any other light in the entire spectrum, can stifle the body’s production of melatonin, a hormone that induces the feeling of sleepiness. Studies show that blue light’s negative effect on melatonin is the primary factor the shifts circadian rhythms and diminishes the ability to sleep. The goal of dark therapy is to remove blue light for at least 10 hours to 12 hours a day for several days, allowing the pineal gland to increase the body’s production of melatonin and re-associate slumber with darkness and sunset.
Therapy often takes place in a window-less, lamp-less room with no surfaces capable of reflecting light. Patients are shrouded in pitch blackness to induce sleep, usually around the time of sunset. In the absence of a dedicated, pitch-black dark therapy room, patients may be given special glasses or goggles with yellow lenses capable of filtering out blue light. Blocking the eyes from any light is crucial since the retina of the eye, upon detecting light or the absence of light, sends messages to the hypothalamus region of the brain, which regulates the body’s sleep-wake cycle.
Considered the antithesis of light therapy, dark therapy is often practiced in conjunction with light therapy, which uses bright artificial light to mimic sunlight and uplift moods. Candidates for dark therapy include those with psychiatric disorders as well as those suffering from mild circadian rhythm disturbances like long-distance travelers suffering from jet lag or new mothers whose body rhythms have been interrupted by the demands of newborns and night feedings. Dark therapy may be administered for up to 14 days at a time in cases of severe disruption, such as is often the case with mania. Users of dark therapy report a range of benefits, including less anxiety, an end to depression, and more mental clarity. Some users are able to lower or end the use of prescribed antidepressants.