The one weather variable that really matters to mental health is the amount of sunlight hours, new research finds.
Rain, air pollution, wind and high or low temperature have relatively little effect.
It is the amount of time between sunrise and sunset that is linked to people’s mental health.
The study’s authors explain the results:
“Seasonal changes in sun time were found to best account for relationships between weather variables and variability in mental health distress.
Increased mental health distress was found during periods of reduced sun time hours.”
Professor Mark Beecher, the study’s first author, elaborated:
“That’s one of the surprising pieces of our research.
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.”
The researchers drew on data from 16,452 people’s emotional health, along with advanced weather information.
They looked at rainfall, solar irradiance, wind speed, wind chill and so on.
But in the end it all came down to daylight hours.
It also didn’t matter if people had seasonal affective disorder or SAD, the results were the same.
Professor Lawrence Rees, a study co-author, explained the genesis of the research:
“Mark and I have been friends and neighbors for years, and we often take the bus together.
And of course you often talk about mundane things, like how are classes going?
How has the semester been?
How ’bout this weather?
So one day it was kind of stormy, and I asked Mark if he sees more clients on these days.
He said he’s not sure, it’s kind of an open question.
It’s hard to get accurate data.”
The study was published in the Journal of Affective Disorders (Beecher et al., 2016).