Q&A on Bright Light Therapy

What is light therapy for winter symptoms, and how is it delivered?

Light therapy involves exposure to intense levels of light under controlled conditions. The recommended light therapy system consists of a set of fluorescent bulbs installed in a box with a diffusing screen, and set up on a table or desk top at which one can sit comfortably for the treatment session. Treatment consists simply of sitting close to the light box, with lights on and eyes open. Looking at the lights is not recommended; rather, people are free to engage in such activities as reading and writing, or eating meals. What is important is to orient the head and body toward the lights, concentrating on activities on the surfaces illuminated by the lights, and not on the lights themselves. Treatment sessions can last from 15 minutes to three hours, once or twice a day, depending on individual needs and equipment used. The average length of a session for a system delivering 10,000 lux illumination is, for example, much shorter than for 2,500 lux (30 minutes vs. two hours). In clinical trials at our institute, with over 100 SAD patients who used a 10,000 lux system with UV-filtered light diffusion and angular tilt, for 30 minutes each day, about 3/4 showed major improvement of depressive symptoms. In another experiment, we found that 30 minutes was an unnecessarily long exposure for some patients (who responded fully at 15 minutes), while several required 1-hour exposures to show the effect.

Early research studies used "full-spectrum" bulbs producing bright light similar in color composition to outdoor daylight, in contrast to the color of ordinary fluorescent or incandescent light. The technology is evolving rapidly, however, and manufacturers now offer effective systems using cool-white, triphosphor and bi-axial lamps. What appears to be critical is that the level of light produced match that of light outdoors shortly after sunrise or before sunset. Light intensity is a critical "dosing" dimension of the therapy: systems deliver varying amounts of light, and people vary in their response to light levels.

The time of day of light therapy is another important factor. Many people with winter depression respond best of all to treatment first thing upon awakening. Some, however, do better with evening light. It is necessary to determine the optimum time of day for each individual.

Is increased exposure to normal room light therapeutic, without the use of special apparatus?

Some very light-sensitive people, living and working in dim environments, may feel improvement with increased exposure to normal room light. Research studies show, however, that most sufferers of SAD and winter doldrums require exposure to light levels much higher than ordinary indoor lamps and ceiling fixtures provide. Such therapeutic levels are five to twenty times higher (as measured in lux or foot-candles by a light meter) than typical indoor illumination in the home or office.

If outdoor light intensities are what's critical, can the therapeutic effect be achieved by spending more time outdoors in winter?

Again, some individuals report improvement by spending more time in the sun. For most, however, the strongest therapeutic effect requires exposure to artificial bright light in early morning - at an hour (6:30 a.m., for example) when it is still quite dark outdoors during long winter nights.

Do the lights really work?

Researchers at more than 15 medical centers and clinics in both the U.S. and abroad have had much success with light therapy in patients with clear histories of SAD for at least several years. Marked improvement is usually observed within a week, if not sooner, and symptoms usually return in about the same amount of time when the lights are withdrawn. Most users, therefore, maintain a consistent daily schedule beginning, as needed, in fall or winter and usually continuing until the end of April, by which time outdoor light is sufficient to maintain good mood and high energy. Some people can skip treatments for one to three days, occasionally longer, without ill effect, but most start to slump quickly when treatment is interrupted.

How do the lights work?

The therapeutic level of illumination has several known physiological effects, though its therapeutic mechanism is still unclear. Blood levels of the light-sensitive hormone melatonin, which may be abnormally high at certain times of day, are rapidly reduced by light exposure. Depending on when bright light is presented, the body's internal clock--which controls daily rhythms of body temperature, hormone secretion, and sleep patterns--shifts ahead or is delayed when stimulated by light. These physiological time shifts may be the basis of the therapeutic response. Light may also amplify the day-night difference in these rhythms. Research into the possible mechanisms is currently underway, and the final answer is not yet in.

Are there any side effects?

Side effects have been minimal. While a small minority of patients experience headaches, eyestrain/irritation, or nausea at the beginning of treatment, these are usually mild and abate after a few days. The most dramatic side effect, which occurs quite infrequently, is a switch to an overactive state, during which one may have difficulty sleeping, become restless or irritable, and feel speedy or "too high." People who have experienced such states in late spring or summer are particularly vulnerable, and guidance by a skilled clinician in the use of light therapy is especially important. If eye irritation persists, it can be alleviated by sitting farther from the lights, using them for shorter periods, or by installing a humidifier. Some people report disturbing sensations of visual glare under bright light therapy, which can be alleviated by use of the tilted light box design described above. A major source of visual glare is short-wavelength blue light, which is a component of the white light used for therapy; such blue light can be screened out by use of special, recently-developed "See-More" eyeglass lenses (or clip-ons) that maximize transmission of longer wavelengths without significantly affecting lux levels (SphereOne, Inc.)

What if I'm pregnant?

Although no hazard is suspected, and some pregnant patients have used the treatment successfully, light therapy has not yet been systematically evaluated during pregnancy. However, three relevant clinical trials (in Connecticut, New York, and Ohio) are underway, covering a variety of interventions for antepartum depression (depression during pregnancy), whether or not the depression occurs in winter.

Do the lights cause tanning?

They should not. Most light therapy systems shield out (or substantially reduce) the ultraviolet light that causes tanning. Occasionally, a person with very sensitive skin shows reddening under full-spectrum lights, in which case complete UV-blocking, with filters, alternate bulbs, or a sun screen lotion is needed. This should not influence effectiveness, however, since the adult eye does not pass UV light to the retina.

When are the lights contraindicated?

Research studies exclude patients with ocular or retinal pathology (for example, glaucoma, cataracts, retinal detachment, retinopathy) and those who might be at risk (for example, predisposing factors of diabetes). No adverse effect of light therapy has been found in ophthalmologic examinations of SAD patients, but because this is a new technology, such caution is warranted.

How did this treatment develop? How long has it been in use?

The first demonstration of clinical effect was at the National Institute of Mental Health in the early 1980's. Soon after, several research centers initiated clinical trials, and more than 2,000 SAD patients have been studied to date. The method has also been used in private practices, mostly by psychiatrists, but also by family doctors and psychologists. The number of clinicians offering light therapy is increasing dramatically year by year, though compared to drug treatments or psychotherapy, the method is not yet in widespread use.

Are the lights medically approved? Is a prescription needed? Does insurance cover their cost?

In the sense that your doctor suggests and supervises the treatment, the method is approved. The Food and Drug Administration, however, has not ruled one way or another, and in this sense the lights are not being considered as a new "medication." People don't need a prescription for lights, but anyone suffering serious depression should certainly seek a doctor's recommendation before obtaining a unit, and use it under the doctor's supervision. Insurance reimbursement for the cost of light therapy apparatus is not consistent. Some people have made successful claims, based on their physician's statement that the lights are medically indicated and effective for the individual. Medicaid does not yet cover this expense. If the insurance policy covers psychiatric care or psychotherapy, it is very likely that it will reimburse for clinical sessions involved in diagnosis of SAD, evaluation for light treatment, and follow-ups.

How much do the lights cost? Can individuals build them for personal use?

This technology is young, and several manufacturers are coming out with new models each year. Prices have ranged from approximately $360 to $500. Design breakthroughs, however, may reduce this price in the future.

We do not recommend home construction of the apparatus. Output must be specifically calibrated for the proper therapeutic effect. A danger of creating electrical or heat hazard exists. Apparatus on the market should have been evaluated for output intensity, visual comfort, maximum transmission with minimal heat build-up -- and, importantly, clinical efficacy in documented research trials. These factors should be carefully checked before purchasing any light system.

What other treatments are available for SAD?

Recently, using a special electronic device, negative ion therapy has been shown to help alleviate symptoms associated with SAD. A negative ion is a molecule that contains an extra electron. These negatively-charged particles are created naturally by the sun, wind, and moving water. Such molecules, in high enough concentrations, are capable of making the air cleaner and fresher. This has been shown to reduce irritabililty and depression in people with SAD, while improving their energy level.


Dawn simulation is another type of light therapy that is currently being investigated. In this treatment, one receives light exposure during the final period of sleep. A lamp is turned on by a computerized timer, which simulates an actual outdoor springtime dawn. This light, which is much less intense than that delivered by light boxes, has been shown to affect the body's biological clock, suppress melatonin secretion, and to have an antidepressant effect. Both negative ion therapy and dawn simulation therapy can be administered while one is asleep. Because of this convenience, these treatment options may be preferable to some.

Although an early study comparing light exposure to the eyes and to the skin found that light to the eyes has the greatest therapeutic effect for people with SAD, a recent study indicates that circadian rhythms (the body's biological clock) can be affected by light exposure to the back of the knee. While this finding will certainly lead to further research, it would be premature to draw conclusions about the potential effects of skin illumination on SAD symptoms. Also, people should take note that exposure to ultraviolet (UV) light, given off by the sun and by tanning lamps, can lead to other health problems, such as skin cancer. People with SAD should definitely not try to "self-medicate" by exposing their skin to potentially hazardous UV illumination.

Aside from these environmental treatments, some sufferers find that standard antidepressant medications provide relief, even if they do not reach their normal level of well-being until spring or summer. Many patients have been in psychotherapy and found it to be helpful to them in many ways -- but unfortunately, not in relieving their SAD symptoms.

photos courtesy of SphereOne, Inc.

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