The science of why the sun makes us feel so happy

Alice Hall
·6 min read
Are you happiest with some sun on your skin?
Are you happiest with some sun on your skin?

Step outside and what is the first thing that you notice? Maybe it’s the groups of six sat chatting happily in the park, or the cheery chirping of the birds. But one thing that everyone seems to have in common this week is a good mood – which could be down to an unexpected but very welcome spell of spring sunshine.

This week, the UK is basking in a mini spring heatwave, with the Met Office predicting that temperatures could rise to up to 24C in south-east England. This conveniently coincides with the gentle easing of lockdown restrictions, the “stay local” message being scrapped and the rule of six coming into place. After months of being stuck inside our homes during one of the bleakest winters on record, this sunny spell is just what the doctor ordered.

But what is it about the sunshine that makes us feel so happy? Here is the science behind why those rays are so good for us.

It boosts our mood

Most of us will agree that it’s hard to feel unhappy in the sun. This is down to the link between sunlight and our serotonin levels – the hormone that makes us feel happy. It’s also why people are more likely to develop Seasonal Affective Disorder (SAD) when the shorter autumn days arrive and we creep into winter with fewer daylight hours.

There is plenty of research to back up this idea. One study undertaken in Australia found that people had higher levels of serotonin on bright sunny days than cloudy ones. Increased levels of this hormone generally lead to greater feelings of satisfaction and calmness and lower levels of depression and anxiety.

There is even research to show that people who use tanning beds may experience more frequent feelings of euphoria, which could explain why people develop a dependence on regular sessions. Although the connection isn’t entirely established yet, researchers speculate this could be down to the way UV light forces melanocytes, the cells that produce dark pigment in skin, to release endorphins. However, most experts also agree that the increased sun cancer risk negates the feel good factor.

Sun improves our sleep

Regular exposure to sunlight encourages the production of melatonin – the hormone which helps to regulate the body's sleep-wake cycle. This encourages feelings of drowsiness, allowing us to drift off easier at night, which leads to us feeling happier in the day. Melatonin also helps to regulate our circadian rhythms – the body's internal clock that signals when to be alert and when to rest – which can be thrown out of sync by exposure to blue light from technology, disrupted work patterns and light pollution.

In turn, this allows us to feel happier. Research shows that our amygdala – the emotional part of the brain – is significantly more reactive after a bad night’s sleep, meaning we are more likely to feel cranky throughout the day if we have spent the night tossing and turning. Time spent in the sun can help us sleep soundly.

Our sex drive is given a lift

Believe it or not, even our sex drive is affected by time spent in the sun, so a spring heatwave is good news for those who have found their libido dampened somewhat in lockdown. Researchers at Medical University of Graz in Austria found that spending just one hour in the sun can boost a man’s testosterone levels by 69 per cent. In turn, this helps to balance mood, sex drive and cognitive function. The experts put this down to the role of vitamin D, which is produced after exposure to sunlight.

It’s the same situation for women. Researchers in China, who conducted a study on post-menopausal women, identified a link between low levels of vitamin D and low levels of oestrogen, the female sex hormone.

Your bones will be given a boost

Vitamin D is also crucial for helping our body to absorb calcium, which is responsible for strengthening your bones. A lack of vitamin D has been associated with both osteoporosis, rickets and autoimmune diseases, such as rheumatoid arthritis (RA).

A review by the Cochrane Library found that the rates of falls in elderly people – which are partly down to the effects of brittle bones – could be cut by more than a quarter if the elderly were given supplements of vitamin D. However, in recent years many studies have questioned how effective supplements are in reducing rates of osteoporosis.

That's not to say that sunlight can't help though: more than 90 per cent of a person’s vitamin D requirement tends to come from casual exposure to sunlight, making it the best source of the nutrient. So how much exposure do we need to boost our health? On average, experts believe we should be aiming for 10–30 minutes of midday sunlight, several times per week. So make sure you head outside for a walk today to get a boost of bone-strengthening vitamin D.

It improves midlife brain health

While most of the research around sunlight and the brain has focused on serotonin levels, a dose of vitamin D could also be good for our intellect. In 2009, scientists from the University of Manchester found that higher levels of vitamin D are linked with improved mental ability in middle-aged and older men. Men in the study were tested for memory and speed recollection, as well as for mood and physical activity levels, before their blood samples were taken. The researchers found that men with higher levels of vitamin D performed consistently better than those with lower levels.

Your eyes need sunlight

Dr Rangan Chatterjee, GP and author of Feel Great, Lose Weight, explains that light is measured in a unit called lux: if we spend 20 minutes outside – even on a cloudy overcast day – we are exposed to around 10,000 lux, compared with 500 lux if we spend time indoors. This is particularly important for children. Researchers at King’s College London, the London School of Hygiene and Tropical Medicine, found that regular exposure to sunlight lowered the risk of nearsightedness – or myopia – in children and young adults by helping the eye produce dopamine, which aids in healthy eye development.

Exposure to natural light can also help to reduce adult eyestrain, which is on the rise during the pandemic due to more screen time and fewer natural breaks in the working day. A poll of 2,000 adults who are working from home found that one in three have eye strain complaints by the end of each day, despite a tenth having three or more lights on in their home office.

It can lower blood pressure

Research conducted by the University of Southampton in 2018 exposed participants with a normal range of blood pressure to ultraviolet light. They found that after exposure, the participants saw a modest decrease in their blood pressure levels, which could be down to the role of nitric oxide stored in the top layers of the skin. When it reacts to sunlight, it causes the blood vessels to widen – moving the oxide into the bloodstream. Long term, having lower blood pressure can reduce your risk of cardiac arrest or a stroke – so even more of an excuse to soak up the rays.