Sun exposure can help suppress an overactive immune system, which could explain why sunlight is used to treat autoimmune diseases like psoriasis. And since white blood cells—which play a key role in fighting diseases and defending the body against infection—increase with sun exposure, moderate amounts of time in the sun are very helpful for your immune system.
But how important is the weather to your happiness, health and mood?
After reading all my nerdy science reasons why we tend to overflow with awesomeness during the summer, you might assume then that people are happier when they are in warmer, sunnier places, right? Well, don't buy your one-way ticket to a tropical destination, just yet. One study found that people were no happier in southern California than in the cold, cloudy, snowy and rainy Midwest (gasp, I know it's hard to believe Los Angelenos). Even though the Midwesterners complained more about the weather, they were overall no less unhappy than the southern Californians.
Other studies point to the fact that while indeed suicide rates are higher in the Arctic circle, they are actually higher in warmer South Korea than in icy Scandinavian countries. Speaking of Scandinavians, they are listed as some of the happiest people in the world, despite their gloomy cold weather, comparatively. Must be all the hygge.
Another factor may be the genetics of different populations, such as genes that play a role in vitamin D metabolism. Seeing hundreds of patients with methylation gene impairments and people with VDR (vitamin D receptor cite) gene changes tend to have lower vitamin D levels and are more prone to mood disorders. Another thing to consider is the diet of very happy people who live in colder, cloudier parts of the world, as traditional diets consist of a lot of wild caught fatty fish—rich in vitamin D.
So does the weather play in a role in your mood, energy and health? Absolutely. But it's actually not nearly as important as what you eat, your social ties, your outlook on life, and your activity levels.