Dr. Michael Terman has been studying how light effects behavior and mood in animals and humans for nearly forty years. He conducts scientific research into why millions of Americans experience Seasonal Affective Disorder (SAD) symptoms like intense carbohydrate cravings, weight gain, low energy and depressed mood in winter. He is an expert in light therapy for SAD. In September of 2009, I interviewed Dr. Terman.
Causes Winter Blues and Seasonal Affective Disorder (SAD)
LD: What is the cause of SAD?
MT: “Later and later sunrise as we go through fall toward winter. It’s as simple as that. For the
population-as-a-whole, people report feeling their worst months of the year starting at the fall equinox and peaking in January and February…
“Our internal circadian rhythm system is genetically designed to rely on the early morning light signal to stay in sync with local time. When that signal is delayed during the [fall and winter,] the rhythm drifts later… Yet our sleep-wake cycle stays fairly constant because workday hours don’t change.”
Circadian Rhythm, Light, and Sleep-Wake Cycles
LD: So you’re saying we still have to force ourselves to wake up at the same time to go to work even though, due to later sunrise, we would be naturally inclined to sleep later?
MT: “Yes. The result: we force ourselves to sleep out of sync with our circadian rhythm, which is a formula for depression.”
LD: If people could get up at whatever time they wanted, would that solve the problem?
MT: “It would reduce the problem to allow human life to swing with the seasons, but not eliminate it.”
Risk Factors for SAD: Genetics and Latitude
LD: Many people with SAD have to endure family members who roll their eyes and tell them it’s all in their heads. Why don’t seasonal light changes affect everyone that way?
MT: “One predisposing factor is genetic vulnerability in two domains: to depression per se, but also to seasonally changing light exposure.
“If you move to the equator, you won’t have seasonal changes in light exposure. The data indicate that the problem is entirely absent only below 18 degrees north latitude, the level of Mexico City. If you move from New York to Florida, the likelihood of SAD is greatly reduced, but not eliminated.”
LD:. A lot of people seem to hate that it gets dark at 4:30 p.m. in winter and find that depressing. But it sounds like you are saying that the problem is not it gets dark early, just that sunrise is later.
MT: “This would be the conclusion from an extensive set of research studies. Light supplementation in the early morning is very effective, while evening supplementation has far less benefit. Biologically, this relates to the internal circadian clock’s specific receptivity to morning light.”
The Link Between Carb Cravings and Depression
LD: But why does the sleep-wake cycle take its toll on mood and increase cravings for carbohydrates? Why doesn’t it show up as, I don’t know, aches and pains or a craving for celery sticks or something?
MT: “Biochemically, a carb load acts as a mild stimulant to the serotonin system. You could call it ‘nature’s Prozac,’ but at too low a dose to do much good. So the result is excessive intake with diminishing returns, and the side effect of weight gain — often 10 to 15 pounds each winter, but sometimes twice that amount.”
Light Therapy for SAD
LD: What can people do to help themselves when suffering from symptoms of SAD?
MT: “Light therapy, as described authoritatively by the non-profit Center for Environmental Therapeutics (CET) should be used as a self-treatment only by people with “winter blues” [a mild version of SAD.] Those with full-blown SAD should do so only under doctors’ guidance and monitoring…The CET developed an online, confidential self-test to measure the degree of seasonal cycling and its severity, and recommend that people get professional help if indicated.”
More information is available at CET, the not-for-profit organization founded by Dr. Terman, and The Center for Light Treatment and Biological Rhythms at Columbia University Medical Center that Dr. Terman directs. Columbia University Medical Center serves the tri-state area.
Millions of people dread the arrival of winter and the depressive symptoms it brings. But some who have discovered SAD light therapy, have a different outlook.
©Lisa C. DeLuca, all rights reserved. It is a violation of copyright law to reproduce this work on the web or for business use without permission from the author. This article was originally published on the web on September 24, 2009. Please contact the author with your reprint request.
This article is for information purposes only and is not a substitute for personal medical or mental health advice. If you are experiencing troubling symptoms please visit a medical or mental health professional in person.