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

Ann MacDonald

Contributor, Harvard Health

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?


  1. Sophie

    I worked as a ski patroller for many years and was outside all days and in all weather. I retired a few years ago and basically became a poster child for SAD depression, weight gain, etc In the summer when I am outside all day the symptoms go away.

    Tried a light box, but it didn’t do much good. My best cure has been a puppy. Puppy needs to get walked every day, regardless of how I feel. Of course a dog lifts your spirits just by being a dog, but for me part of it is getting out of doors and into the fresh air every day without fail.

  2. Anonymous

    I think there is some truth to this. Summer always seem happier and you wear colorful dresses. But during winter I tend to wear browns and blacks and wish spring would hurry along!

  3. Bob

    Is there a reverse? I love the Summer months and can’t wait till they get here. I know many people that are the reverse – can’t wait to see the snow and go skiing. Me – if I never went outside in the Winter I would be happy. I live in upstate NY so we can get some pretty brutal winters.

  4. Kelly Morris

    The snow makes everyone happy. As long as you have warm clothes lol. I like the blog.

    [URL removed by a moderator.]

  5. kingzrule2

    Exercise also helps. Living on the West Coast for years and then moving to the Northeast again brought on my SAD during the winter. The cold weather makes is difficult to really enjoy being out in the sun.

    • Ann MacDonald
      Ann MacDonald

      Good point! Regular physical activity helps boost mood and is often recommended for people with mild to moderate depression (including SAD). And there are physical benefits as well! Thanks for writing.

  6. Online Health Guy

    Does SAD varies from country to country. For example in a country spring is responsible for SAD and in another winter is responsible?

    • Ann MacDonald
      Ann MacDonald

      Interesting question! An article published in the Journal of the American Medical Association, and posted on the Society for Light Treatment and Biological Rhythms website, reports that SAD is more common in people living in the northern latitudes, such as the United States, Canada, and countries in the northern part of Europe. And while most people who develop SAD do so in the winter months, some also have a “summer” version that is not well understood. You can read more in the JAMA article. Thanks for writing.

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