How Seasonal Affective Disorder Twists Our Decisions

Seasonal affective disorder doesn’t just affect you–it affects the whole economy. We shine some light on why you’re depressed in the darkest months and what we can do about it.

How Seasonal Affective Disorder Twists Our Decisions
[Image: Flickr user D. Sharon Pruitt]

Consider Stockholm, London, Frankfurt, and Toronto. Each of them has stock exchanges, each of them have dark winters. Weirdly enough, you can see the weather in the stocks.


As University of Toronto professor Lisa Kramer and her colleagues have found, seasonal affective disorder doesn’t only show up in your mood–it’s also present in the stock markets. For as the days grow shorter, we feel less and less like taking risks. As Kramer’s research has found, the further you–or a stock exchange–is from the equator, the more likely your behavior’s going to show risk aversion.

Used with permission of the American Economic Association

As Kramer explained to us, the stock markets show behavioral patterns that have a long, long inheritance:

Our brains are these interesting combinations of stuff that affect the way we make decisions, so as the seasons change, our moods can also change, and some of us experience very extreme changes in mood with changes of the seasons.

As the exposure to daylight diminishes, we respond in a biological way to the change in exposure to daylight. We’re not that different than ancestors who would retreat in the winter time. When the seasons changed they had to become a lot more conservative, they had to adopt a lot more conservative practices. We’re still those same people.

What this shows is that our psychology and behavior is super influenced by our environments. Studies have shown that we’re more creative in the dark and less productive in the cold. As anyone who has felt drained by overexposure to fluorescent lights can tell you, light is a major driver of the way we feel. The most profound of these may be what was causing those Swedish markets to get risk averse: Seasonal Affective Disorder.


First put into psychological language in 1984, seasonal affective disorder (with the unfortunately fitting acronym of SAD) is a way of capturing the way that 10% of Americans are intensely affected by their exposure to sunlight.


How do you know if you have SAD?

As University of Rochester psychiatry professor Michael R. Privitera told us, you may experience symptoms of depressive moods during the fall and winter that are frightening for you, your waistline, and your colleagues.

On top of weight gain and excessive sleepiness during the daytime he says, SAD can cause your mood to swing, which can alter your productivity. Plus, he notes, decreased energy and disrupted sleep can compound those difficulties.

But do not lose hope: there’s lots you can do to work better with the dimly lit seasons. Privitera’s recommendations include:

  • To avoid dark environments
  • To get as much daylight as possible during the winter
  • To take a walk outside as soon as possible after waking up
  • To exercise daily, preferably outside
  • To sit near a window when possible, whether in an office, classroom, or restaurant
  • To consider setting up a light device if you can’t get to a window
  • To improve your sleep hygiene
  • To wake up at the same time every day
  • To travel to a sunny, warm climate if possible

But as Kramer, the economics professor, would remind us, we shouldn’t just be aware of seasonal affective disorder in ourselves or in the markets: we should also consider it in the people we interact with.

The Bottom Line:

“Just about every decision we make is something based on risk,” she says. “I write research papers. The work I do is controversial in my field. I noticed I often submitted in the fall when (editors) were least likely to take a risk. Fall and winter–these are not good times to take a risk. If you’re pitching something that’s new and a little crazy, you want to think about the timing.”


About the author

Drake Baer was a contributing writer at Fast Company, where he covered work culture. He's the co-author of Everything Connects, a book about how intrapersonal, interpersonal, and organizational psychology shape innovation.


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