by Patricia McManus

Reprinted from MD Magazine - January 1984

 

Does your spirit wane with the shortening days? You may be suffering from sunlight withdrawal.

The syndrome appears with inevitable regularity. As summer pales into autumn, the victim feels an ominous sense of anxiety and foreboding at the mere thought of approaching winter. As days shorten from November into December, there's a gradual slowing down, a loss of energy, a need for more and more sleep, a longing to lie undisturbed in bed.

 

It becomes harder to get to work, to accomplish anything when there. Depression and withdrawal follow. As a Brooklyn, New York, woman described it, "Everything seems gloomier and more difficult. There is a sadness looming over everything. I can't concentrate at work and feel like going home afterward to hibernate like a bear."

 

Just as routinely, as spring approaches and days stretch out, the sufferer flips into high gear. "Once the warm weather arrives, I feel a burden lifted," says the Brooklynite. "I feel freer and happier."

 

This is more than a dislike of icy slush and raw winds. Psychiatric researchers at the National Institute of Mental Health (NIMH) have identified these complaints as a previously unrecognized clinical syndrome. They call its victims "winter depressives."

 

"It is much more common than we thought," says Dr. Norman Rosenthal of NIMH. "We expected to get a few replies from our description of this pattern. Instead, we received more than three thousand responses from all over the country. The symptoms described were one after the other very much the same."

 

Some of these winter depressives are being successfully treated, not with drugs or psychotherapy but with an element common to all our lives: artificial light. What scientists are learning from the use of light as it affects health and mood has implications for us all. It forces us to rethink the way we light up our lives, especially urban dwellers and workers who spend so much time indoors. Apparently artificial light does much more than enable us to read and work without benefit of sunlight. It affects our bodies.

 

"It is important to recognize that this is a distinct syndrome with a well-defined cluster of symptoms," says Dr. Thomas Wehr, an NIMH researcher. "We have measured some very interesting physiological changes specific to this kind of depression."

 

While typically depressed people have impaired sleep patterns and usually wake up early, winter depressives might sleep nine or 10 hours a night, wake up tired, and take naps. There is a 50% reduction in delta sleep, the deepest, most restful phase of the sleep cycle. Winter depressives gain weight, crave carbohydrates, and their libido pales. Their energy levels drop; monitors on their wrists show that they are less active than in summer.

 

Such symptoms begin earlier the farther north they live and abate. When they visit sunny southern climates in the winter. Symptoms peak and wane according to the length of days. In New York, for instance, on the shortest day of the year - December 21 - the sun rose at 7:17 A.M. and set at 4:32 P.M., contrasted to 5:25 A.M. and 8:31 P.M. at the height of summer, a six hour difference in light. Such a distinct seasonal pattern implicates the external environment as the culprit, the most obvious being sunlight.

 

Sunlight has already been shown to trigger cycles and seasonal behavior in animals, including reproduction, hibernation, migration, and molting. Animal behavior has been fooled by artificial light. Could it also fool humans? Apparently.

 

In a recent NIMH study, a group of these depressives were treated with amounts of light that simulated that of summer days. Short winter days were stretched by six extra hours of light. The subjects were awakened before sunrise to bask in three hours of light, and dusk was delayed for three more hours.

 

Since sunlight is thought to be the missing element, the subjects were flooded with an artificial light that most closely resembles the full broad spectrum of the sun, a fluorescent tube called "Vita-Lite." At 20 times the intensity of normal indoor lighting, the light approximated the sensation of sitting on a shady porch or under a tree in mid-summer. Fluorescent lamps are roughly three times more intense than ordinary light bulbs.

 

A bank of eight 40-watt fluorescent bulbs at eye level lit the participants' rooms as they read, worked, or moved around. Within days this group responded with measurable mood changes, says Rosenthal. Their symptoms eased and energy levels rose, while a control group with a different threshold of light showed no change in behavior.

 

"Something in the external environment caused these changes," says Wehr, "but we are not prepared to say exactly what it is at this point. It is true, though, that waking up these people and exposing them to this light treated their symptoms. Whether it is the break in sleep pattern, the wavelengths or intensity of light, or some other factor we can't say at this point. We don't know if the Vita-Lite is the essential element, although it may be."

 

The intensity of light used in the study may be well in excess of what is necessary to effect changes, stress the researchers. So they will continue to experiment with varieties of light therapy to determine the crucial element. The subjects themselves feel that sunlight is the missing ingredient. One said that she felt as if she were in a "lower state of evolution since I function by photosynthesis."

 

Although these winter depressives showed an abnormal response to light, each of us responds to it in varying degrees. External light travels on a direct pathway from the retina to the part of the hypothalamus believed to be involved in running our biologic clock, the suprachiasmatic nuclei. The path continues to the tiny, cone-shaped pineal gland, which secretes the hormone melatonin. It is thought that melatonin affects the regulation of behavioral changes in animals, but this has not been clearly shown in humans. Sufficiently intense light suppresses the secretion of this chemical, making it a useful marker in determining light's physical effect on behavior.

 

The secretion of melatonin reflects light's effect on the hypothalamus, itself highly sensitive to light. This complex part of the brain regulates a multitude of body functions, playing a vital role in reproduction, thirst, hunger, satiation, temperature, emotions, and sleep patterns. Depression is associated with disturbances in the hypothalamus.

 

"By stimulating the hypothalamus with light we may be correcting these disturbances in this group," explains Rosenthal.

 

Most artificial light differs from natural sunlight in wavelength (color) and intensity. Sunlight is very intense electromagnetic energy in a continuous spectrum of colors ranging from the short wavelengths of invisible ultraviolet light (UV) through blue, green, yellow, and into the infrared waves. The majority of our homes are lit by incandescent bulbs that light through heat. They lack the intensity of sunlight and produce light that is heavily infrared.

 

"We don't like the incandescent lights," says Wehr. "It's conceivable for this purpose that they are not the safest. You can get burned from the heat and the infrared radiation.

 

Although some fluorescent lamps are described as "broad spectrum," they do not have the same distribution of colors as sunlight. Widely used fluorescent lights peak in the yellow-green portion of the spectrum, wavelengths to which the eye is most sensitive. That makes them energy efficient but different from natural sunlight, notably in the blue-green spectrum where the sun's emission or radiant energy is strongest. Additionally, conventional indoor lighting lacks the proper proportion of near-UV radiation of the sun that advocates claim to be vital to health and well-being.

 

This is a pivotal point in the world of lighting. The Vita-Lite bulb purports to be healthy for plants, animals, and people because it is so close to natural sunlight. Skeptics say that the need for an indoor equivalent of sunlight has yet to be proved, especially given that UV radiation has been linked to skin cancer. Believers in Vita-Lite say that sunlight is essential to living creatures and that the large blocks of time we spend indoors deprive us of sufficient amounts, including UV.

 

Just as overexposure can be unhealthy, regulated doses of sun and UV can be therapeutic. UV is currently used to treat psoriasis and, experimentally, genital herpes and some forms of cancer in the early stages of the illness. Full-spectrum artificial light is widely used to cure a potentially fatal type of infant jaundice. We need sunlight with its UV rays to metabolize vitamin D, necessary for the absorption of calcium, especially in growing children and the elderly.

 

Some studies show that working under true full-spectrum lights enhances productivity and reduces fatigue. Even critics concede that many people who are deprived of natural light, such as night or shift workers, suffer undue emotional stress.

 

Whether or just how we should alter our indoor lighting is a question being raised by these studies. As Dr. Richard Wurtman, professor of endocrinology and metabolism at the Massachusetts Institute of Technology, has been saying for years, we should not take artificial lighting for granted. Lined up in the pro-sunlight camp, he has written, "Light is potentially too useful an agency of human health not to be more effectively examined and exploited."

 

As researchers isolate the specific part of the sun's spectrum that is related to health and well-being, we could eventually create the perfect indoor environment with artificial lighting, says E. Woody Bickford, environmental engineer with Duro-Test, manufacturers of Vita-Lite. "Until we know," he points out, "Vita Lite, with its complete range of visible and invisible light, is what we have to work with."

 

For ordinary indoor lighting, two to four 40-watt lamps would provide some health benefits, he says. "The benefits seem to be proportional to the amount of light," he adds. "We may need higher intensity in all our work levels. Perhaps the cutoff point is what you can afford." Vita-Lite tubes are expensive, and most of our homes are not equipped with fixtures that can accommodate them.

 

Although many lighting experts are skeptical of the entire concept of light affecting our health, some light manufacturers are beginning to support research in the field, and one trade association has just established a new branch devoted to light and health.

 

As the relationship between light and health becomes publicized, NIMH's Rosenthal worries that people will try to treat themselves. "With the winter depressives it's a matter of risks outweighing benefits. Bright light can damage the retina; UV can be dangerous. But depression can be dangerous for them, too!"

 

Rather than attempting to cure themselves, people who think that they are winter depressives should contact the NIMH, Bethesda, Maryland 20205, for literature and specific recommendations as they become available. As Dr. Wehr puts it, "we are not telling people to hurry and turn lights on - not yet."