In many parts of the world, there’s a deeply ingrained belief that sunny days make us feel more cheerful. It seems like common sense, but the scientific evidence is surprisingly equivocal.
Yes, there are individual studies supporting the link – for instance, in 2013, researchers at the Freie Universität Berlin reported that people surveyed on exceptionally sunny days felt more satisfied with life than people surveyed on cloudier days. However, an earlier and larger influential paper led by Humboldt-University in Berlin involving over 1,000 volunteers found no evidence that people enjoyed more positive moods on sunnier days (although they did tend to feel less tired).
Flipping things around, even the idea that many of us are more prone to depression in the gloomier the winter months (known as ‘seasonal affective disorder’) is controversial. For instance, a US study involving over 38,000 participants failed to find any link between sunlight exposure and risk of depression. In short, the evidence for the mood-enhancing effects of sunshine are not as robust as you might think.
When it comes to sunshine and health, however, the scientific evidence is more clear cut. While too much sunshine is undoubtedly bad for your unprotected skin, sunlight exposure is also beneficial in many ways because it allows the body to create more vitamin D, which can reduce the risk of cancer and lower blood pressure among other health benefits.
Morning exposure to sufficient daylight is also important for entraining the circadian rhythm, which is important for healthy sleep. So, while excessive sunbathing is unwise, so too is closeting yourself indoors without any sunlight at all.
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