Shining A Light On Seasonal Affective Disorder

To get you through the dark days until springtime, psychiatrist Dr. Edwin Tam at the University of British Columbia’s mood disorders centre explains how seasonal affective disorder works.

1. What is it?

Seasonal affective disorder is a subtype of major depressive disorder or bipolar disorder, wherein those afflicted only experience symptoms during autumn and winter. Those include oversleeping, extreme fatigue, difficulty concentrating, changes in appetite with carbohydrate craving and weight gain. With more severe episodes comes a sense of worthlessness or guilt, and people may have suicidal thoughts.

“We would diagnose it the same way we would diagnose a depression, which is that basically you’ve got two weeks in a row of feeling either down or just losing interest, a lack of joy,” Tam said. “Are you slowed down, kind of fidgety? It’s hard to get to work, you’re not socializing as much.”

If any five of those symptoms persist, it could be SAD.

2. What causes it?

Research has shown that light has an effect on brain chemistry and function.

“Animals who hibernate are actually cued in on how long the days are,” Tam said. “You can fool an animal in the lab into thinking it’s wintertime by making the days artificially shorter — by turning out the lights earlier (in the evening), turning them on later in the day.”

Tam said they believe some people respond similarly to the length of the day.

“Other people, it could be the jet-lag hypothesis; you get up in the morning, and in the winter it’s dark out. So even though your alarm clock is saying 7 a.m., you’re looking outside and your eyes may be saying no, my body clock is telling me get back to bed, it’s dark outside,” he said. “There’s something about the morning light in particular … in the winter, because it’s so dark, we’re not getting that morning signal. You always feel out of synch.”

Others find that it’s not about the length of daylight, but how bright it is. “I’ve had some patients report that if it’s really sunny in the winter, it eliminates (depression) for them.

“I don’t know there’s one model that fits everybody,” Tam said.

3. Is it worse in rainy, cloudy Vancouver than elsewhere?

“They haven’t been able to find that strict pattern of correlating rainfall with more SAD,” Tam said. “Anecdotally, just in my practice, I’ve had people who swear that it was harder for them when they came out to B.C. or Vancouver in particular, from let’s say Ontario. Back east, it was a lot more sunny, and there’s lots of snow on the ground, so it’s double bright. Snow reflects the light.”

Tam said surveys have indicated that while fewer than one per cent of Florida residents suffer from SAD, as many as 10 per cent of Alaskans show symptoms. Canadian studies put the number of sufferers somewhere in the middle, at between one and three per cent.

As many as 15 per cent of Canadians suffer from milder forms of winter depression. “A lot of people will just tough out a winter depression themselves.”

4. Most common treatment?

“Using a light box or a light book, bright-light therapy in the morning time,” Tam said. “First, it makes the day longer, and it also gives you that morning signal.”

Tam said some patients who don’t have the time to take half an hour a day under the lights are prescribed antidepressants.

The specially designed light boxes alleviate symptoms in 60 to 70 per cent of those who use them, and they cost between $100 and $300.

“They’re much brighter than room lights,” Tam said. Indoor lights have an intensity of between 600 and 700 lux, while the light boxes used in SAD treatment put out 10,000 lux.

Doctors don’t recommend that you build your own light. The lights are screened so that they don’t emit ultraviolet light. “We want it bright, but not tanning your skin.”

Summer sunshine at noon can be as high as 100,000 lux, Tam said.

5. What should I do if I think I have SAD?

Everyone who is significantly depressed should be assessed by a family doctor, because some physical problems (such as thyroid disease) can show up as depression. People with SAD can be treated by the family doctor, referred to a psychiatrist, or (in Vancouver) referred to Tam and his colleagues at UBC for further assessment. People should not treat themselves with light exposure until after assessment by a qualified health professional.

People are cautioned not to use suntanning studios to treat SAD. The effect of light therapy is through the eyes, not through skin exposure, and people should not open their eyes in tanning booths because of the harmful effects of ultraviolet exposure.

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