The best prescription is nature itself
"Here's your prescription, walk in the forest five times a week for an hour."
According to experts, it is not inconceivable that doctors will be giving health advice like this in the not too distant future.
After decades of research, the scientific world is moving closer to pinpointing how exposure to nature seems to promote well-being.
A recent US study found that being close to nature might soothe the mind by reducing rumination - when negative thoughts get stuck on repeat, playing over and over in the mind.
A team at Stanford University compared the effects of taking a nature walk through a greenspace with a stroll in an urban environment - in this case beside a busy road in Palo Alto.
Brain scans showed reduced activity in an area of the brain linked to risk of mental illness in participants who took a 90-minute walk among oaks, birds and squirrels.
They also reported lower levels of rumination.
Gregory Bratman of Stanford University, one of the researchers on the study, says moving to cities has "happened in a blink of an eye in terms of human evolution".
As he points out, never before have so many of us been removed from nature - already 50% of the global population lives in towns and cities; a figure that is projected to rise to 70% by 2050.
Some cities and nations are already thinking about the mental health benefits of nature when designing urban areas.
"There's an increasing body of evidence showing that natural versus urban areas benefit us at least emotionally with our mood and possibly also our cognitive development too," says Mr Bratman.
"You could think of these mental health benefits of nature as a psychological ecosystem service."
The Stanford University team is looking at ways to tease apart the "active ingredients" of the nature experience to find ways to bring nature into the city
Greening up towns
Meanwhile, Britain's Royal Horticultural Society is trying to encourage the public to bring nature into their own backyard, by replacing concrete with plants.
A garden at the Hampton Court Flower Show for the Greening Grey Britain campaign showcased ways to make urban environments rich in both vegetation and nature.
Plants from the garden are to be moved to Bristol to green-up a street for the community, including St Mungo's hostel for the homeless.
Nigel Dunnett, Professor of planting design and vegetation technology at the University of Sheffield, is behind the garden.
He says we "evolved with nature and it's completely unnatural for us to be separated from it".
He wants a shift in thinking to make developers invest in providing natural surroundings and for horticulturalists to get involved in green infrastructure projects.
"There is a big role for horticulture in this whole movement of greening cities," he adds.
"We have to be really radical, really innovative to get into places where you normally wouldn't get to see things growing."
One health trend that is popular mainly in Japan and South Korea is Shinrin-yoku, a term that means "taking in the forest atmosphere" or "forest bathing".
A study conducted in 24 forests across Japan found that walking among trees lowered blood pressure, the pulse rate, and levels of the hormone cortisol, which is released in response to stress.
According to psychologist Dr Mathew White of Exeter University, research into the link between nature and well-being is increasingly focussing on effects on the body and brain, such as how brain activity corresponds with the nature experience.
"It does start to tell us some of the cognitive elements that could be at play in why urban environments are so taxing to the brain," he says.
He says several projects are underway to try to develop "green prescriptions" for exposure to nature that would be of benefit people going through anxiety or depression.
The Stanford University research is published in the journal, Proceedings of the National Academy of Sciences.