Harvard Health Publications

Feeling S.A.D.? Lighten up if it’s seasonal affective disorder

Posted By Ann MacDonald On January 26, 2011

This picture shows the view from my office window in Boston: dull, dreary, and depressing — at least on overcast days like today. Lack of light is one of the reasons that people feel mentally foggy. One of the bloggers I follow, Rachel Zimmerman of WBUR’s CommonHealth blog, recently wrote that she’s been drinking three times as much coffee as usual. In addition to imbibing more caffeine, I’ve been trying to boost my spirits and alertness with midday runs to the snack machine (not the best strategy, in case you’re wondering).

At this time of year, many people aren’t just foggy and sad—they’ve got S.A.D., or seasonal affective disorder. About half a million Americans — women more often than men — are diagnosed with seasonal affective disorder each year. Many others experience at least some of the symptoms, which include loss of pleasure and energy, inability to concentrate, feelings of worthlessness, and an uncontrollable urge to eat sugar and high-carbohydrate foods (in my case, chocolate chip cookies).

Bright white light therapy remains a mainstay of treatment for seasonal affective disorder. That’s because the light acts on cells in the retina, the tissue located at the back of the eye that sends visual information to the brain. The hypothalamus, which helps control the sleep/wake cycle, is one part of the brain that receives this information. During the winter months, when people tend to stay indoors more, days are shorter,  and the weather becomes overcast, our exposure to natural light diminishes. That disrupts the sleep-and-wake cycle, as well as other circadian rhythms. The result can be symptoms of seasonal affective disorder.

Fluorescent light boxes deliver traditional bright light therapy. People usually expose themselves to 30 minutes of light, at an intensity of 10,000 lux (a measure of illumination), upon arising each day. (By way of comparison, indoor light is about 100 lux, while a bright sunny day is 50,000 lux or more.)

But traditional light therapy doesn’t work for everyone; only about 50% to 80% of people get complete relief. Moreover, side effects of bright light therapy, while mild for many people, may be more of a concern for others. For example, bright light therapy may trigger hypomania or mania in people with bipolar disorder, which is why doctors recommend they take mood-stabilizing medications at the same time.

There’s also a small risk of retinal damage from light therapy. Some medications (such as melatonin and St. John’s wort) and medical conditions (diabetes or retinopathies) increase the risk.

The FDA does not test, approve, or regulate light box devices. Anyone considering buying a device should ask about the wavelengths it emits and check to see if it has been used in any reputable research facilities.

More information about seasonal affective disorder and its treatment is available through the Society for Light Treatment and Biological Rhythms. (Look for the tab called “Public Info” on the left column.) The Center for Environmental Therapeutics also provides information about seasonal affective disorder, and offers tips about how to find a good light box.

For people like me, who experience mild symptoms, the best strategy is to go outside during the day — morning is best — rather than hibernating indoors (or making endless runs to the snack and coffee machines). Exposure to natural light can also help to restore your body’s natural rhythms — and perhaps boost your mood and mental functioning as well.

What do you suggest? Do you have any other ideas or resources to share with readers of this blog?

Related Information: Improving Memory: Understanding age-related memory loss

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