The scientific reasons that gardeners are nicer than other people

Science proves that gardening makes you happier, healthier, calmer and smarter.

Science proves that gardening makes you happier, healthier, calmer and smarter.

OPINION: I edit NZ Gardener magazine and so I spend a lot of time meeting and talking to other gardeners. And I have long thought that gardeners are, on the whole, happier, smarter and less stressed than any other group of people I knew.

Up until now, I had only my own anecdotal experience to draw on, but it seems that there is real scientific evidence to back up this view.

I happened to be talking to Dr Heather Hendrickson, a senior lecturer in molecular bioscience at Massey University, who is an expert in the evolution of bacteria. She mentioned that there is a bacteria living in soil called Mycobacterium vaccae, commonly referred to as M. vaccae. When you come into contact with this bacterium the serotonin levels in your brain go up, she said, so effectively working with soil improves your mood. So gardening really does – scientifically – make you happy.

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Hendrickson told me there are thousands of bacteria in soil – there have been estimates of anything from between 2000 and 830,000 different species of microbes in every gram of dirt. M. vaccae is just one of those bacteria. It's closely related to Mycobacterium tuberculosis, which is the causative agent of tuberculosis, and the scientists wanted to find out if it could be used therapeutically, so they gave it to patients suffering from lung cancer. And the patients reported that not only had their symptoms eased, they felt a lot happier about everything too.

At that point, Hendrickson told me, these scientists started to wonder if this particular bacterium has the ability to improve people's moods. To find out, they did some tests on mice, and mice exposed to M. vaccae, Hendrickson says, were less stressed than mice that weren't. (Now I'm sure you, like me, immediately want to know how they measure stress responses in mice. Heather says they put the mice in tiny mouse-sized swimming pools and see how long they'll swim for – a stressed mouse will give up quite quickly.)

Eventually they managed to figure out that being exposed to this soil-dwelling bacteria stimulated a certain set of neurones in the mice's brains; which contributed to serotonin production. They also discovered that the mice were significantly better at solving mazes, even a couple of weeks after being exposed to these happy-inducing soil-dwelling microbes.

There's overseas examples too. Last week the BBC released a story calling gardening a new wonder drug, after a report by the independent charity The King's Fund, which works to improve health care in the UK, suggested it should be prescribed by the NHS. Gardening could be shown to reduce the risk of heart disease, cancer and obesity, the report found, and it improved people's balance, reducing the risk of falling for older people. Other studies have shown gardening reduces depression, stress and anxiety.

I think we can all see what the data is suggesting. Gardeners are happier, smarter, less stressed and healthier than other people. So, can I just say: well done science… but I knew that already.

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 - NZ Gardener

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