A study has shed some light on why many of us feel happiest during the summer months.
They found mental health distress increased among the population during times of the year with reduced hours of sunlight, but improved during the lightest seasons.
They suggested this finding applies to the population as a whole, not just those diagnosed with Seasonal Affective Disorder (SAD).
To analyse links between mental health and the weather, three scientists joined forces to bring data from their individual fields.
Mark Beecher, clinical professor and licensed psychologist in BYU Counselling and Psychological Services, was able to provide insight into the times emotional distress was most reported using emotional health data from clients.
Meanwhile, Lawrence Rees, a physics professor at BYU, had access to weather data.
Finally, they were joined by BYU statistics professor Dennis Eggett to identify links.
The study took weather variables into account such as wind chill, rainfall, solar irradiance, wind speed, temperature and more.
The trio concluded that “seasonal increases in sun time were associated with decreased mental health distress”.
Notably, they found that days with a high amount of sunshine, even when they were interspersed with cloudy or stormy moments, appeared to have the most positive impact on our wellbeing.
“That’s one of the surprising pieces of our research,” said Beecher.
“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.”
He urged therapists to be aware that winter months may bring a high demand on their services.
“With fewer sun time hours, clients will be particularly vulnerable to emotional distress,” he said.
“Preventative measures should be implemented on a case-by-case basis.”
The study only looked at trends in data between sunshine and mental health, rather than analysing the reasons behind the link.
However, previous studies have suggested our vitamin D levels may influence our mental health.
A report by the Isfahan University of Medical Sciences in Isfahan, Iran, found that people who had vitamin D deficiencies were also more likely to suffer from mental health conditions than those with good levels.
In particular, they found that 65% of participants who had schizophrenia had “significantly” lower levels of vitamin D in their blood compared to people without the condition.
The latest study is published in the Journal of Affective Disorders.