The students of Gradale Academy in midtown Toronto are on their way to a place they call "Mud Mountain" for some outdoor time that may offer an antidote to everyday problems affecting their physical and mental health.

Situated near their school around the trails of the Don Valley, "Mud Mountain" is, yes, dirty and mucky. Armed with clipboards, the students, who range from kindergarten to Grade 6, examine the foliage and wildlife of an early spring day.

But researchers believe nature offers more than just its beauty; it offers serious academic and mental-health benefits.

A recent review of hundreds of studies has found mounting "evidence of a cause-and-effect relationship": Experiences in nature led to improvements in attention span, self-discipline and physical fitness, all while reducing stress.

Researchers also found that children with attention deficit hyperactivity disorder (ADHD) who take a 20-minute walk in a park can improve their symptoms as effectively as if they took a dose of prescription stimulant medication.

Dr. Melissa Lem is a family physician in Vancouver. She believes in the power of greenery.

"There are two different major theories as to why nature is good for your brain, and one of them is called Stress Reduction Theory. Essentially, it speaks to how humans evolved in nature," she said.

Because we humans have been surrounded by forests, flowers, and fauna for most of our existence, scientists believe there may be an evolutionary reason that nature feels to us like a comfortable, familiar place.

There's also what's called the Attention Restoration Theory, first developed in the 1980s, which proposes that exposure to nature is not only enjoyable, but can also help us improve our focus and ability to concentrate. Nature, says Lem, is simpler and less taxing than the crowds, lights, traffic, and noise of city life.

Michelle Gradish, who runs Toronto's Gradale Academy, believes even an hour a day spent outdoors can help children learn. (Craig Chivers/CBC)

"It doesn't tire out your concentration. It just lets you kind of enjoy and restore your brain."

Michelle Gradish, who's been running the Gradale Academy for 18 years, is a firm believer in outdoor education. She says even an hour a day spent in nature can teach students how to cope with the unexpected.

"They don't even realise that they're learning at that point, as opposed to when they're inside and at their desks and they're almost told what to do and how to do it."

Nature and mood

Meanwhile, a group of students at Toronto's Ryerson University has found that nature breaks reduce their stress and make it easier for them to handle their workload.

Every week, they participate in Mood Routes, a program run in partnership with the Canadian Mental Health Association. They visit parks, greenhouses and nature trails all over Toronto, with the goal of boosting health and fitness, as well as improving their state of mind.

"[Nature's] green. I guess I equate that with [feeling] happy and with healthy," said Natalie Pavlovich, a 26-year-old psychology student at Ryerson who has joined the Mood Routes.

"I think when you're [immersed] in green, your troubles go away and you feel pure."

A recent study backs that up. Researchers at the University of Michigan say that taking at least 20 minutes out of your day to take a walk somewhere close to nature can lower your stress hormone levels.

"For the greatest payoff, in … efficiently lowering levels of the stress hormone cortisol, you should spend 20 to 30 minutes sitting or walking in a place that provides you with a sense of nature," said lead author MaryCarol Hunter in a news release.

Hunter is a landscape architect and ecologist with an interest in the effect that experiences in nature can have on mental well-being.

Deena Shaffer runs Mood Routes, a program at Ryerson University whereby students who are stressed and lonely take revitalizing walks in parks, greenhouses and nature trails around Toronto. (Craig Chivers/CBC)

Participants in the experiment were asked to spend 10 minutes or more in nature at least three times a week over eight months. Hunter's team took saliva samples to measure cortisol levels before and after the leisurely walks, which were taken without conversation or smartphone interruptions.

Deena Kara Shaffer, the coordinator of student transitions and retention at Ryerson, runs the weekly Mood Routes. She's seen students who are stressed, lonely, and exhausted become revitalized after visiting a garden, forest, or park.

"They connect with a perspective of something larger than themselves, which can be really helpful if you're studying, really fixed on one thing," she said.

Back at Mud Mountain, Gradish's students are noting the nests and plants that are part of the Don Valley ecosystem.

Gradish believes that learning in natural settings promotes warmer, more co-operative relationships, and teaches lessons that will last a lifetime.

"They have matured in ways with their leadership skills, with their teamwork, and with their confidence."