Insomnia is often a disharmony in the circadian rhythm and our biological clock. Our bodies’ natural sleep-wake cycle is stimulated chemically by changes, or cues, in the lightness and darkness of our surrounding environment. For most animals and humans, the darkness that night brings stimulates a release of melatonin in the brain. This subsequently provides the natural effect of drowsiness.
Our circadian rhythms and sleeping rhythms can easily become disturbed due to stress, intoxication, allergies, eating habits, various diseases/disorders, and other lifestyle factors. Our circadian rhythms are driven by light. Light over 5000 lux can impact our rhythms so that it can change the onset and timings of our rhythms. This is literally what sun light does to our body clocks. As soon as we get enough light (note: even the cloudiest day light exceeds artificial light) into our body system (through our eyes), signals are sent throughout the body. This in turn changes the timing for the release of hormones and neurotransmitters which drive our metabolic cycles. As a summary, light has a key role adjusting our body clock. This also means that light therapy – either sunlight or electrical lights – can be used to balance our disturbed circadian and sleeping rhythms.
Bright light therapy
Sunlight therapy consists of sitting/walking/spending time outdoors for a sufficient duration at a certain time of the day. Electrical light therapy consists of using ultraviolet and/or infrared therapy sun lamps. Both sunlight and electrical light therapies have shown good results in adjusting sleeping latency and quality with no negative side effects. This assumes that short-term use of electric sun lamps or sensible exposure for natural sun light (not taken during mid-day and not burning the skin).
In the management of circadian rhythm disorders such as delayed sleep phase syndrome (DSPS), the timing of light exposure is critical. For DSPS, the light must be provided to the retina as soon after spontaneous awakening as possible to achieve the desired effect, as shown by the phase response curve for light in humans. Some users have reported success with lights that turn on shortly before awakening (dawn simulation). Morning use may also be effective for non-24-hour sleep-wake syndrome, while evening use is recommended for advanced sleep phase syndrome.
Bright light therapy, as it’s called, is the practice of exposing a patient to a bright light source as a biological clock stimulus. The theory is that this brighter light mimics the effects of normal daylight, but is more intense.
DSPS patients (delayed sleep phase syndrome, ie waking too early) can be treated successfully with bright light when they awaken.
ASPS patients (advanced sleep phase syndrome, ie much earlier sleep cycle than normal) can be treated before they go to sleep and to keep them from sleeping too early in the afternoon or evening.
Your biological clock is tricked into responding to bright light, either to stave off sleep or induce waking earlier, therefore prompting a more normal release of melatonin and time appropriate sleep-wake cycle.
The light therapy products available range from sunlight visors you wear like a hat to a whole room full of spectrum lighting and even high-tech dawn simulators. Each has a particular application, so consult with your doctor. In many instances a light therapy product prescribed by a doctor will be covered by your insurance plan.
Many ancient cultures practised various forms of heliotherapy (classical term for light therapy), including people of Ancient Greece, Ancient Egypt, and Ancient Rome. The Incan, Assyrian and early German settlers also worshipped the sun as a health bringing deity. Indian medical literature dating to 1500 BC describes a treatment combining herbs with natural sunlight to treat non-pigmented skin areas. Buddhist literature from about 200 AD and 10th-century Chinese documents made similar references.
Light therapy requirements
In fixed light therapy we expose our bodies to direct light at particular times. We simply go outdoors regardless of the weather: it can be sunny or cloudy. Timing depends on the kind of adjustment we want to make to our body clock. The more skin is exposed, the better.
By exposing the face to early morning light resets our body clock to the earlier part of the day. When we repeat this for days or even weeks we start to affect our cortisol and melatonin release cycles – together with many other hormone and neurotransmitter cycles. As a consequence we become sleepier earlier in the evening and more awake earlier the next day.
Full-spectrum laps can also partially reset the body clock. However, the amount of light needed to perform this task is between 5,000-10,000 lux. This said, full spectrum bright light boxes can be a good investment for someone who has trouble getting outside or lives in an extreme northern or southern location.
Sitting by a window doesn’t generically do the trick. Staying too long in the direct sun light can expose to skin cancer. Experts seem to agree that 20-30 minutes in the morning would be a good amount of sun light treatment. It has been thought that light actually has to penetrate the retina in order to have an effect. Further study revealed that even blind people got the benefits of light therapy.
Rotational Light Therapy
A person can move his/her sleeping schedule and patterns with clock rotation therapy in a few days. The easiest way to do this is to forward several hours per day until one’s clock is rotated to the desired cycle.
If we wish to sleep sooner in the evening and wake up earlier in the morning, we could start so that we stay up until 2-3 am the first night followed by 6-8 hours normal sleep. The next night we would stay awake until 5-6 am and again sleep our normal 6-8 hours. The following night we would stay awake until 8-9 am followed by our normal sleep hours. And so on until the sleeping rhythm is at the desired spot. This rather well-tested progression of the sleep cycle adjusts the body clock forward allowing us to completely reset our daily sleep patterns.
The brightness and colour temperature of light from a light box are quite similar to daylight.
The production of the hormone melatonin, a sleep regulator, is inhibited by light and permitted by darkness in the retina. To some degree, the reverse is true for serotonin, which has been linked to mood disorders. Hence, for the purpose of manipulating melatonin levels or timing, light boxes provide very specific types of artificial illumination.
Light therapy may use a light box which emits up to 10,000 lux of light, much brighter than a customary incandescent lamp. Newer light therapy devices use LED technology, making them much smaller and more convenient for users.
In treatment, the patient’s eyes are to be at a prescribed distance from the light source with the light striking the retina. This does not require looking directly into the light.
Considering three major factors – clinical efficacy, ocular and dermatologic safety, and visual comfort – CET recommends the following criteria for light box selection
- Light boxes should have been tested successfully in peer-reviewed clinical trials.
- The box should provide 10,000 lux of illumination at a comfortable sitting distance. Product specifications are often missing or unverified.
- Fluorescent lamps should have a smooth diffusing screen that filters out ultraviolet (UV) rays. UV rays are harmful to the eyes and skin.
- The lamps should give off white light rather than coloured light. “Full spectrum” lamps and blue (or bluish) lamps provide no known therapeutic advantage.
- The light should be projected downward toward the eyes at an angle to minimize aversive visual glare.
- Smaller is not better; when using a compact light box, even small head movements will take the eyes out of the therapeutic range of the light.
Risks and complications
Ultraviolet light causes progressive damage to human skin. This is mediated by genetic damage, collagen damage, as well as the destruction of vitamin A and vitamin C in the skin and free radical generation. Ultraviolet light is also known to be a factor in the formation of cataracts. Researchers have questioned whether limiting blue light exposure could reduce the risk of age-related macular degeneration.
Modern phototherapy lamps used in the treatment of seasonal affective disorder and sleep disorders either filter out or do not emit ultraviolet light and are considered safe and effective for the intended purpose, as long as photosensitizing drugs are not being taken at the same time, and in the absence of any existing eye conditions. Light therapy is a mood altering treatment, and just as with drug treatments, there is a possibility of triggering a manic state from a depressive state, causing anxiety and other side effects. While these side effects are usually controllable, it is recommended that patients undertake light therapy under the supervision of an experienced clinician, rather than attempting to self-medicate.
There are few absolute contraindications to light therapy, although there are some circumstances in which caution is required. These include when a patient has a condition that might render his or her eyes more vulnerable to phototoxicity, has a tendency toward mania, has a photosensitive skin condition, or is taking a photosensitizing herb (such as St. John’s wort) or medication.
Side effects of light therapy for sleep phase disorders include jumpiness or jitteriness, headache, and nausea. Some non-depressive physical complaints (such as poor vision and skin rash or irritation) may improve with light therapy.