Sunshine matters. Pollution, rain, the temperature... not so much. That's the takeaway from a new study from Brigham Young University that tracked the effects of a whole windsock full of atmospheric and meteorological conditions on our mental and emotional health.

The bit about the benefits of sunshine you probably could have predicted. We understand intuitively how a sunny day has a similar effect upon our dispositions. But you also likely guessed that dreary days dragged us down, in kind. And there you'd be wrong.

“That’s one of the surprising pieces of our research,” said Mark Beecher, clinical professor and licensed psychologist in BYU's Counseling and Psychological Services. “On a rainy day, or a more polluted day, people assume that they’d have more distress. But we didn’t see that. We looked at solar irradiance, or the amount of sunlight that actually hits the ground. We tried to take into account cloudy days, rainy days, pollution... but they washed out. The one thing that was really significant was the amount of time between sunrise and sunset.”

We are ringing up our therapists and counselors more frequently in the winter months not because it is damp and stormy, but because there are just fewer hours of sunshine. More hours of darkness make us more vulnerable to emotional distress, the researchers concluded.

BYU's is not the first study to look at the weather’s effect on mood, but Beecher believes it is the most meaningful to date due to the following four reasons:

• The study analyzed several meteorological variables such as wind chill, rainfall, solar irradiance, wind speed, temperature and more;
• The weather data could be analyzed down to the minute in the exact area where the clients lived;
• The study focused on a clinical population instead of a general population;
• The study used a mental health treatment outcome measure to examine several aspects of psychological distress, rather than relying on suicide attempts or online diaries.

The weather data came from BYU’s Physics and Astronomy Weather Station, and the pollution data came from the U.S. Environmental Protection Agency. Mental and emotional health data came from BYU’s Counseling and Psychological Services Center.

The study was published in the Journal of Affective Disorders.