Apart from making music, what do Hank Williams jnr, the Beatles, the Violent Femmes and more than a hundred other musicians and bands have in common? For the purposes of this column, the answer is they’ve all recorded songs with the word “sun” in the title (All for the Love of Sunshine, Here Comes the Sun and Blister in the Sun, respectively).
Physiologically, exposure to sunlight is associated with the production and regulation of various chemicals – most notably melatonin (involved in regulating sleep) and vitamin D (which we synthesise from cholesterol and need for regulating calcium and phosphate levels). Exposure to sunlight is important as it helps us regulate our internal timekeeping – take away the sun and we start to lose our sense of day and night. And it’s not just us. Other mammals appear to detect seasonal change through the changing number of daylight hours. For mammals (think hibernation, fertility and foraging behaviours), this is important for survival.
On the quirky side, look no further than “Extraocular circadian phototransduction in humans”, written by Scott Campbell and Patricia Murphy and published in the journal Science in 1998. The pair sought to demonstrate that, as with some other organisms, circadian cycles aren’t influenced just by our seeing sunlight but also via the circulatory system. They did this in experiments by shining light on the back of the knee. Sadly, more recent research suggests this fascinating finding may be the result of spill of light from behind the knee to the eyes (their eyes weren’t perfectly shielded from the light). Pity, because it led to a great media frenzy.
Sunshine is also about temperature, of course. If it’s too low, we die. And if it’s too high? Well, we die as well. If, like me, you have ever suffered as a result of a dodgy air-conditioning thermostat in your workplace, you’ll know 14°C isn’t conducive to productivity. The occupational safety and health information about “temperature at work” for people in sedentary occupations recommends that for “thermal comfort”, temperatures should be between 19°C and 24°C (in summer) and 18°C and 22°C (in winter). Interestingly, research suggests cognitive performance peaks at about 22°C.
Sunshine is also important for our psychological well-being, the most obvious example being the slightly contentious concept of seasonal affective disorder, the depression-like symptoms that seem to affect some people more than others in winter. Even those of us who don’t experience this kind of extreme seasonal mood fluctuation typically show some effects at different times of the year – we just tend to feel happier and more optimistic as the days get longer. But – and it’s a big but – this doesn’t mean travelling the globe to avoid winter will make Jack a happier, healthier and wealthier boy. It turns out the mood-elevating effects of sunshine occur because they follow winter’s dearth of sunlight – a contrast effect.
One of the side effects of walking on sunshine is that we tend to be slightly less risk-averse than we might otherwise be – and this translates into a variety of fascinating results. For instance, shares bought on unusually sunny days tend to bring higher returns not because of some mysterious solar influence on their value, but rather because the nature of trading on such days is different. Conversely, we tend to overindulge more when the sun doesn’t shine – our self-control is “depleted” and so we’re more likely to splurge on chocolate, alcohol and even lottery tickets.
Of course, too much careless sun can have serious effects; it’s hard to work and concentrate when it’s 40°C, and the mood also dips as the heat goes on. Once again, things just can’t be simple and it all becomes a matter of finding the perfect balance. Darn it.