Tom Court invites me to bend down and crawl through a holly bush. As the waxy leaves scratch at my arms, I feel this is a slightly prickly introduction to the Japanese practice of Shinrin-yoku, or forest bathing. Tom is from Hill Farm, a yoga and wellbeing retreat centre in Tintern, on the Welsh side of the Wye valley, and he explains to our small group that the holly tree acts as a gateway to the woods and is all part of experiencing the forest on a new level.

The woods in question are glorious: tumbling in layers across the steep hills above Tintern Abbey. The roots of beech trees clamber over moss-covered dry stone walls and ferns line rain-washed gullies.

We settle down in a glade and learn that while the practice of forest bathing only began in Japan in the 1980s, it is a natural development from the Shinto religion. Shinto devotees believe human life and nature are linked through the transferral of energy, and trees and rocks are inhabited by kami spirits.

In Japan there are 62 designated forest-bathing woodlands, and doctors prescribe sessions to patients suffering from high blood pressure, anxiety and depression. Forest bathing is also thought to boost the immune system.

For those sceptical of the power of rock gods, scientists have proven that spending time beneath the trees does have measurable benefits.

Trees give off chemicals called phytonicides, which they use to ward off disease and insect attack. Two hours’ walking in the forest is thought to be more beneficial than antidepressants, with the effect lasting up to 30 days. It is like Radox for the mind, and perhaps the perfect antidote to these troubled times.

We start our session with a short meditation before being asked to remove our walking boots and stroll barefoot up a rocky path. Tender-footed city dwellers inch forward gingerly, tiptoeing through the prickly beech mast on the forest floor.

“It certainly puts you in the present,” one of the group says. “I’m not thinking about anything else at the moment other than where I should place my feet.”

The leaf litter is crumbly underfoot, like slightly damp coffee grounds, and mud squishes between my toes but my feet are thanking me. Suddenly they are released to enjoy the warmth of the soil and the soft water in a puddle, sensations they are usually denied. They begin to zing with pleasure, little bolts of electricity zipping through them, as if they are on holiday.

“Walking barefoot is thought to be one of the best antioxidants there is,” Tom says.

I can believe it, and decline to put my shoes back on when we are given the option.

Later, as I sit in the lap of a pine tree while Tom encourages us to listen in to the sounds of the forest, I can feel myself slowing down, becoming more centred. I hear two flies fighting, and the deep sigh of the woman next to me, who confesses that she really needs this after months of being stuck inside. The wind picks up, a soft pillow of sound and raindrops fall from the leaves, sounding like the feet of marching ants. As we grow quieter, the forest grows louder and birds approach to within feet of us, curious as to why these humans are suddenly silent.

Tom then leads us through a series of games. We partner up and eyes closed, are led through the woodland, before snapping our eyes open to reveal tiny details – a starry clump of moss, the light filtering through birch bark. We play, “meet a tree” and run our hands around the chunky warmth of gnarled trunks.

For those wanting something more in-depth, Hill Farm runs weekend retreats, which include yoga, gong showers, an open-air spa and longer meditation sessions, where guests can connect with the trees more deeply.

However, even this introduction is having an impact. My feet feel supercharged with cushiony warmth and my other senses have awoken too. I notice for the first time the toffee-apple scent of old pine needles. I taste the lemony zest of wood sorrel; even the colours of the woodland flowers seem more intense.

I am not the only one feeling the benefit. By the end of the session, Carla, a marketing manager, is making new plans. “I haven’t felt this calm in weeks,” she says. “It’s made me realise I really want to live closer to the countryside. My children are young, I want them to grow up near the woods.”

It seems beneath the loamy and dappled beneficence of the trees, life-changing things can occur.

• Three-hour forest bathing sessions with Forest Retreats cost £30pp. It also has full-day retreats including yoga, forest bathing, vegetarian lunch and an outdoor spa from £70; and weekend retreats including camping, yoga, gong meditation and vegetarian meals, from £225