Our species spent most of its evolutionary history in equatorial regions, where dawn and dusk came gradually at much the same time all year around. Countless centuries later, our brain is still geared to expect a similar daily pattern of light and darkness, even though we have largely migrated to latitudes where the days are longer in summer and shorter in winter. This displaced position on earth still overwhelms the influence of man-made interferences: streetlights, room lights, and late-night TV and computer light. Human migratory patterns have produced predictable but often unrecognized effects on our mood, energy, and sleep.
One such effect presses on us now as we move toward winter. Winter blues and its more severe relative, seasonal affective disorder (SAD), are marching in. The symptoms of SAD—gloom and despair, excessive sleep, food cravings, pervasive anxiety, among others—add up to a major depression. Yet there is one big difference from unpredictable depressions: its timing, with the clear link to light deprivation in winter. Getting too little light, or getting enough but not at the right point in the day, puts you at risk for up to half a year of relative agony.
Fortunately, the cause implies a cure. Getting enough light, and at the right time, offers a way of dealing with the problems created by light deprivation. By restructuring the amount and pattern of our daily light exposure, we can achieve remarkable therapeutic results, even in cases of severe depression or sleep disorders. Best of all, the intervention is environmental, not pharmaceutical. The most widely known method is bright light therapy. This involves sitting in front of a therapeutic light box of a particular brightness, for a particular length of time, at a specific time of day (usually in the early morning). Each user needs to experiment at the start to find his or her optimum settings.
The therapeutic technology is evolving, bringing the light signal more toward the equatorial ideal. Of course, daylight and nighttime do not turn on and off with the flick of a switch. Rather, the eyes and brain received the signals gradually, at levels well below full daylight.
Dawn (and dusk)
Michael under a broad light diffuser, with graphs of simulated summer and winter dawns.
Terman lab, Columbia University
simulation, or DDS, is the translation to the bedroom. In Michael’s early research, volunteers with SAD placed a contraption next to their beds that made the light level gradually rise just as it would if they had been camping out under the open sky in springtime. Very quickly, they were sleeping through the first light of dawn and waking spontaneously when the level reached that of sunrise. And their depression lifted, sometimes in as little as a week. In other studies, people with insomnia at bedtime found it easy to go to sleep during simulated dusk, to sleep through the night, and to wake refreshed at simulated dawn, about eight hours later.
Dawns and dusks throughout the year, halfway between the equator and the north pole.
Terman lab, Columbia University
Our new book, Reset Your Inner Clock
, describes the next steps being taken with DDS technology and applications. A new class of precision device is under development, and on the docket for availability to the public. First it will undergo testing in a residential facility where researchers will be able to take data on mood and sleep. The device includes a computer-chip controller with flexible dawn-dusk adjustments, hooked up to a large, diffused-light source that gradually floods the entire top of the bed with light at a time that simulates morning at a particular latitude and time of year. At bedtime, the light level just as gradually declines into darkness. The speed of the naturalistic signal varies according to the choice of seasonal pattern and geographic location. The optimum speed of the up-and-down transitions will vary from person to person just as the duration of a bright light therapy session needs to be individually dosed.
Meanwhile, entrepreneurs have jumped on the dawn simulation wagon, without paying attention to the need for research and verification. You can easily buy a “dawn alarm clock,” with built-in lights that gradually get brighter over some preset length of time, usually shorter than any sunrise on earth. Some of these even come with radios, MP3 players, and built in bird sounds, not to mention aromatherapy. If you like the idea of being awakened gradually by a bedside lamp that plays music, smells like spruce or lavender, and trills like a lark, you might enjoy using one of these gadgets. But you should not expect to get the same results that bright light therapy or clinical dawn simulation offer. For that, you’ll need equipment and an approach that has been tried and validated in clinical research. You can learn more from the recommendations in our book or at our website.
Michael and Ian are co-authors of the 2013 Penguin paperback, Reset Your Inner Clock. They invite you to follow them on Twitter for news updates, opinions, and challenging Q-and-A’s. If you want to stay on top of body-clock matters, light therapy, and more — and take advantage of confidential, online self-assessments of inner clock time, depression, and seasonality — you should become part of the nonprofit Center for Environmental Therapeutics community. Email PTuser@cet.org so we can stay in contact.