With the end of daylight saving time on Sunday, the nation’s after-work commutes will soon be cloaked in darkness. The good news is that, come spring, it’ll start getting sunny again. The bad news is that, according to a big new study, hours of sunshine — not temperature, pollution, or rain — has a significant effect on the way people feel.
Lead-authored by Brigham Young University psychologist Mark E. Beecher and published in the Journal of Affective Disorders this month, the study makes use of a deep, detailed, and somewhat narrow data set: 16,452 students who came to BYU’s counseling services over a six-year period.
The researchers matched client’s ratings on a 45-item self-reported mental-health questionnaire at the start of each counseling session with data on sunrises, sunsets, rainfall, wind, pollution, and other weather variables collected by the university’s physics department and the National Weather Service. They found that the more hours of sun there was in a given day, the less psychological distress people had.
“We were surprised that many of the weather and pollution variables we included in the study were not significantly correlated with clients’ scores on the distress measure once we had accounted for sun time (the time between sunrise and sunset),” Beecher explained to Science of Us in an email. “People tend to associate rainy days, pollution, and other meteorological phenomena with sadness or depression, but we did not find that.” While he’s not sure what’s so special about sunshine, it does seem, at least according to the therapy clients in this study, that the amount of sunshine in a day is crucial to emotional well-being.”
The paper adds a degree of clarity to a field with lots of contradictory findings: Another 2016 paper found no link between seasonality and depression, while a 2013 paper found that people people have higher life satisfaction when the weather is nice. There are limits to this study, since it only surveyed a relatively homogeneous sample of students at a religious school in the American west; similar work would have to be done in populations in different cities with different locations to see if it would hold up as a replicate across contexts.
What data seems to suggest is that seasonal affective disorder, which the American Psychological Association describes as a depression lasting through the winter months, may be the extreme form of something everyone experiences: As the days darken, so do moods. So gather ye koselig while ye may.