Light Therapy

The Science of Natural Light’s Healing Properties

The Science of Natural Light’s Healing Properties

Background & History

Many people will be surprised to learn that light therapy has been used in clinical settings for almost 60 years. Since the 1950s, medical practitioners have used light panels to treat patients with depression, sleeplessness, and other mood disorders.

In the early days, to avail themselves of the healing properties of bright light, patients had to go into hospitals, doctors’ offices, or convalescent spas and stand in front of a wall length panel of light. Treatments were generally long, up to several hours. The results were good but use was limited. There was innovation in the field and by the 1980s, light therapy devices were smaller boxes, but there were still unattractive and unwieldy. And treatment sessions still lasted as long as two hours.

Through new technology and updated design, light therapy can now be administered at home or in the office. It’s possible to gain the benefit of the soothing and uplifting properties of light in brief sessions of just 15–30 minutes using an attractive table lamp designed to emit the right light frequencies. When you consider where we’ve come from, you could certainly say, we’ve come a long way.

What Is Light Therapy?

Light therapy or phototherapy consists of exposure to specific wavelengths of light using lasers, LEDs, fluorescent lamps, dichroic lamps or very bright, full-spectrum light, for a prescribed amount of time. It has proven effective in treating seasonal affective disorder, sleep problems, low mood, jet lag, shift work problems, and skin conditions. It has recently also been shown effective in treating non-seasonal depression.

How Do You Get S.A.D.?

Because sunlight is limited in winter, often people experience low mood, feelings of depression, sadness, or the “blues.” This condition is said to affect at least 3% of the population in northern countries like Canada, and is also widely experienced in Scandinavia and other European countries and northern states in the US. This has an effect on productivity and self esteem and has become a more widely recognized problem in recent years. With exposure to bright light, individuals can experience a significant shift in as little as a few days.

Is It True that Light Therapy Can Really Help Seasonal Affective Disorder (SAD)?

Physicians have long been advising their patients to seek adequate light as a necessary component of health. It was only in more recent years though that scientific research has been able to show how important bright light exposure can be to our physical and mental health.

Over 20 years ago, Dr. Norman Rosenthal and colleagues published their seminal theories describing the use of artificial bright light to alleviate symptoms of Seasonal Affective Disorder (SAD). Their work hypothesized that by lengthening the daily exposure to light in Northern latitudes--in essence recreating summer length days—would bring about the reduction of depression symptoms in the darker winter months.

While they may have pioneered the way, subsequent studies around the world have continued to experiment with bright light as a treatment for winter depression and mood disorders. As studies became more refined, researchers discovered that it is not essential to replicate the precise length of summer daylight. They found that if a patient received a photic pulse, of as little as 30 minutes, that would emit the necessary signal to the nervous system and boost spirits.

Generally this treatment is highly safe although patients with eye abnormalities or conditions should always consult with their physicians and regularly repeat eye examinations to ensure safe exposure conditions are met.

A breakthrough for light therapy occurred in 2005 when an American Psychiatric Association work group concluded that light could be used as a “first-line” treatment for both seasonal and non-seasonal depression. This was significant, marking light’s emergence as a viable alternative or addition to drug therapy for depression.

Another area where bright light therapy has proven beneficial is in the treatment of certain sleep disorders. There are several types of sleep disorders: advanced sleep phase syndrome (ASPS) and delayed sleep phase syndrome (DSPS). In ASPS, there is premature sleep onset and early morning awakening. In delayed sleep phase syndrome (DSPS) individuals have trouble getting to sleep before 1 a.m. and have a hard time getting up at a regular workday time. This type of sleep disorder is often associated with disturbed circadian rhythms, which effect both body temperature and the level of melatonin secreted by the pineal gland. When bright light therapy is applied in the morning it can correct phase delayed patients. When applied in the evening it can adjust phase advanced patients. In both cases it has proven to be very effective in “resetting” patients’ internal clock enabling them to adjust to normal living schedules.

There are numerous applications of bright light therapy which are being tested for effectiveness. Any symptoms which recurs seasonally, are more heightened in the winter, or could be related to low outdoor light exposure are prime candidates for light treatment. Several symptoms and conditions that show promise in early research studies include: depression during pregnancy, premenstrual depression, adult attention deficit hyperactivity disorder, bulimia nervosa, binge eating disorder, shift work fatigue, jet lag, and behavioral disruptions of Alzheimer’s disease including sleep and daytime agitation.

What Is Dawn Dusk Simulation (DDS) Therapy?

Dawn and dusk simulation (DDS) therapy provides a major departure from standard bright light therapy in the following ways:

  • DDS therapy is used while in bed, during normal sleep hours. By contrast, bright light therapy is used during waking hours.
  • DDS therapy presents gradually changing light levels to mimic outdoor dawn and dusk transitions (when the sun is below the horizon). The maximum required light intensity is around 300 lux. By contrast, bright light therapy presents constant light at supra-sunrise levels (say, 10,000 lux).
  • DDS is a more practical, “automatic” treatment in that it hardly requires the user’s attention, and most of the signal is presented while the user is asleep. By contrast, bright light therapy requires scheduling waking hours for treatment.

It seems that Dawn Dusk Simulation therapy is very effective but to date there have been far fewer clinical tests than for other light therapy treatments. In general, most tests use a dawn signal (without the corresponding dusk signal). The preliminary results show: increased ease of awakening, with more alertness and energy, and an antidepressant effect. Combined dusk and dawn signals are more promising than a single application. Scheduling the dusk fade at bedtime, and the dawn at wake-up time has brought good results. People who have had difficulty falling asleep report having an easier time getting to sleep.

Light therapy lamps for DDS vary in design. You’ll want to choose a lamp and fixture that illuminates the sleeping area in a diffuse light and that touches the eyes as your sleeping posture varies.

DDS therapy was first tested in the late 1980’s by Drs. Michael Terman and David Schlager at Columbia*. They relied on a box that had a precision motor rotate a set of vanes, which were placed in front of a fluorescent light box. In essence, this operated like a computer-controlled Venetian blind. Although the mechanics were cumbersome, several important effects were noted:

  • The dim dawn signal cut the body’s production of melatonin in the morning hours. This likely contributes to ease of awakening.
  • One specific effect was shown that after a week of daily home exposure to a naturalistic dawn set for early May (but delivered in midwinter), the circadian rhythm of melatonin production shifted to an earlier hour. What does this mean? The dawn simulation had a physiological effect similar to an eastward time zone transition.

Terman and Schlager concluded that “twilight exposure appears able to promote circadian phase adjustments, morning melatonin suppression, regularized sleep patterns, and antidepressant responses. This represents the first indication in humans of physiological and/or behavioral sensitivity to such light signals.” Underscoring the logic of DDS vs. bright light therapy, the authors continued, “We hypothesize that non-modulated bright light constitutes a supernormal stimulus [that is, a stimulus with higher intensity than required under natural conditions]. The eyes may be primed at twilight hours for reception of changing intensities of low-level light.”

More contemporary DDS lamps, which can be used at home, rely on electronic controls and use more common incandescent/halogen lamps. Patients choose ideal times for simulated sunrise. In one popular strategy, patients choose their preferred sleep length (for example, 7.5 hours). Specialized DDS lamps include microprocessors which can locate a point on the earth that matches this nighttime duration at the summer solstice, and adjust the lamps accordingly. This sophisticated technology is a big advance on previous lamps. When users begin DDS therapy, they need to experiment and find the most effective combinations of light intensity, twilight duration, and timing. Most people choose a sunrise of around 300 lux, but others require lower levels to prevent premature awakening. Far lower levels are often preferred for the dusk signal.