Sunnier Day, Sunnier Disposition?

Do you feel cheerier on a sunny day? Or gloomier on a cloudy one? Many of us have the impression that sunlight affects our moods. For me, this was brought home some years back, when I spent a week in Portland, Oregon. As typical of the Pacific Northwest, it was cloudy the first few days, but I paid it little notice, while enjoying the casual laid-back pace of the city. Then, about the fifth day of my visit, I noticed my mood perking up. It soon occurred to me that for the first time that week, the sun was finally peeking through the clouds.

How people are affected by sunlight has become a focus of scientific study. We know, for example, that some people experience a diagnosable mood disorder, called seasonal affective disorder (appropriately abbreviated as SAD), during the fall and winter months and only bounce back as sunnier weather returns in the spring and summer. SAD is a type of major depression—technically, major depressive disorder with seasonal pattern. We don't know what causes SAD, but researchers suspect a reduction in ambient sunlight may disrupt the body's biological rhythms or perhaps reduce the availability in the brain of the mood-regulating neurotransmitter serotonin. People who suffer from SAD may be helped by moving to sunnier climes or by undergoing a form of treatment called phototherapy, in which they sit under intense artificial light for hours at a time during the fall and winter months.

Even people who don't suffer from SAD tend to experience weather-related changes in moods. Studies by environmental psychologists show that people are somewhat chipper in the spring than the winter. However, as the heat of summer wears on, people's moods tend to dampen a bit (Keller et al. , 2005). This may be why many people report feeling better with the arrival of fall weather. Although you can't control the weather or summon the winter sun to bathe you in a warm glow, you can adjust to changes in ambient light by spending time outdoors on sunny wintry days and limiting exposure to darkened indoor environments, such as avoiding long afternoons at the local multiplex.

Exposure to bright light can also have effects on the intensity of emotional expressions, and not necessarily in positive ways. As reported on ScienceDaily, Canadian management professor Alison Jing Xu notes that most people tend to report feeling better on sunnier days, but people who are prone to depression often report feeling more depressed. Xu believes that exposure to bright light intensifies emotions one way or the other, either boosting good moods or deflating negative ones. She points to evidence that suicide rates tend to peak during late spring and early summer months. She and colleague Aparna Labroo found in their own research that exposure to bright indoor light can even increase preferences for spicier foods. It seems that exposure to bright light may intensify emotional responses. One lesson to draw from this line of research is that if you want to keep a lid on a heated discussion with a spouse, it might be best to dim the lights a bit, or avoid stirring things up while walking down the aisles of brightly lit supermarkets.

References

Keller, M. C., Fredrickson, B. L., Ybarra, O., Côté, S., Johnson, K., Mikels, J., . . . Wager, T. (2005). A warm heart and a clear head: The contingent effects of weather on mood and cognition. Psychological Science, 16, 724–731

The way a room is lit can affect the way you make decisions. ScienceDaily, February 20, 2014.

Xu, A. J., & Labroo, A. A. (2014). Incandescent affect: Turning on the hot emotional system with bright light. Journal of Consumer Psychology, 24, 207-216.