Forest Therapy Gains Scientific Ground as Evidence-Based Mental Health Intervention

A growing body of scientific evidence is elevating forest therapy from a wellness trend to a clinically relevant mental health intervention. A 2021 systematic review published in the International Journal of Environmental Research and Public Health, which examined studies on forest therapy spanning 1990 to 2020, found that the practice was consistently associated with improvements in depression (search)Search disease and anxiety (search)Search disease symptoms—both in healthy individuals and in people diagnosed with these conditions. While the authors note that more research is needed to clarify mechanisms, the findings signal that forest therapy may offer meaningful, accessible mental health benefits.

What Defines Forest Therapy

Forest therapy is an umbrella term encompassing a range of activities—meditating, walking, playing games, or socializing—conducted in a forest environment with the explicit goal of promoting well-being. What distinguishes it from simply being outside is a deliberate, sensory-aware engagement with the natural surroundings.

"Simply going for a walk in a forest isn't going to yield the most meaningful outcomes," said Stephanie Freitag, PhD, a licensed clinical psychologist. "We need to pair the activity of forest bathing, walking, or hiking with mindfulness, which is to be truly present with our sensory experiences."

Jessica Meers, a clinical psychologist, underscored the contrast with modern daily life: "Many people spend their days in a constant state of stimulation, notifications, traffic, deadlines, screens, and endless demands on their attention. Time in nature gives the nervous system a chance to settle."

The Neuroscience of Nature

Susan Abookire, a Harvard Medical School assistant professor of medicine at Brigham and Women's HospitalView company profile, guides monthly forest therapy walks for medical residents and faculty—a population at elevated risk of burnout. Her two-hour sessions at the Arnold Arboretum draw on the Japanese practice of shinrin-yoku, or "forest bathing," immersing participants in nature to counterbalance the high-stress hospital environment.

Research has demonstrated that engaging with nature activates the parasympathetic nervous system—the "rest and digest" state—which counterbalances the sympathetic nervous system responsible for the body's fight-or-flight response. "When you're busy working all day on a screen and have emails and problems to solve and using your frontal cortex, basically, that is subject to fatigue," Abookire said. "You are exhausted even though you haven't moved out of your chair all day and that kind of exhaustion can be restored when you go outside and pay attention and just sit and smell the grass."

Meers added that natural light plays a critical role in circadian rhythm regulation, supporting healthy sleep and relaxation. She also noted that nature "gently captures our attention, without demanding anything from us. Unlike scrolling through a phone or responding to emails, it allows the brain to engage without becoming overloaded."

Fractals, Terpenes, and the Healing Environment

Abookire highlighted the role of fractals—infinitely complex, self-similar patterns found throughout nature in snowflakes, crystals, and leaf veining—in promoting physiological resonance. "If I showed you a picture of a cube and ask you, 'Is this nature?' you would say no because nature doesn't have those sharp square edges," she said. "But when we are experiencing fractals, whether it's sound or sight patterns, our bodies resonate with that."

Plants also emit fragrant compounds called terpenes that have drawn scientific interest for their therapeutic potential. Studies have demonstrated anti-inflammatory properties of d-limoneneView drug details, found in rosemary, coniferous trees, and citrus rinds. CarvacrolView drug details, a terpene in oregano and thyme, has shown cancer-fighting potential. BorneolView drug details, present in ginger and some cannabis strains, has been studied for its anti-inflammatory and neuroprotective effects and as a potential Alzheimer's treatment.

Although research into nature's effects on cancer outcomes is only recently emerging, Abookire noted that multiple studies have established that nature exposure improves cancer patients' quality of life. Even indirect exposure appears beneficial: one study found that patients viewing nature from a hospital window recovered faster than those facing a brick wall, while another showed that participants looking at a green roof exhibited higher attention spans than those viewing concrete.

Building a Sustainable Practice

Experts agree that consistency outweighs intensity. "A single walk in the woods can boost mood, but the real benefits come when spending time in nature becomes a regular practice," Meers said. Starting with just 5 to 10 minutes of mindful outdoor time daily can compound into meaningful mental health gains over time. Research suggests that as little as 20 mindful minutes in nature three times a week can yield benefits, though Abookire emphasized that "the more the better."

Both Freitag and Meers stressed the importance of disconnecting from devices during forest therapy. Freitag also recommended bringing a notebook to record thoughts, feelings, and sensory reactions that arise during the experience. "Substantial research suggests that mindfulness plus gratitude are the key to well-being," Freitag said. "Notice how you perceive the environment through the five senses while acknowledging the joyousness and beauty of nature, which is so easy to take for granted."

Abookire also runs a six-month program accredited by Mass General Brigham (search)Search term that trains medical professionals as Nature as Medicine Practitioners, signaling growing institutional recognition of nature-based interventions within mainstream healthcare.