5. The Forest as a Therapeutic Environment: What Does the Evidence Establish?

5.1. Introduction: Understanding the Therapeutic Potential of Forest Environments

A substantial and expanding body of scientific literature has examined the relationship between natural environments and human health. Over recent decades, research in environmental psychology, environmental physiology, public health, neuroscience, immunology, and related disciplines has contributed to understanding how exposure to natural environments may influence human functioning. Within this broader field, forests have received particular attention because they provide complex combinations of sensory, physical, atmospheric, biological, and ecological conditions that may be associated with psychological restoration, physiological stress regulation, and subjective well-being.

Despite the increasing number of studies reporting favourable outcomes following forest exposure, the question of what makes a forest environment therapeutic remains considerably more complex than identifying measurable physiological or psychological changes. Evidence that individuals experience improvements in selected health-related indicators after spending time in forests does not necessarily establish that the forest functions as a clinical treatment, that particular environmental mechanisms are responsible for the observed outcomes, or that professionally organised experiences produce greater benefits than independent engagement. Furthermore, forests are not uniform environments, and individuals do not enter them with identical physiological conditions, psychological expectations, sensory preferences, cultural backgrounds, or personal relationships with nature.

The distinction between the therapeutic potential of an environment and the demonstrated effectiveness of a particular intervention is therefore fundamental. It requires examining not only what happens to individuals during forest exposure, but also which environmental characteristics may contribute to their responses, how individuals interact with these conditions, and what conclusions can reasonably be drawn from the available scientific evidence. This distinction is particularly important in the context of Shinrin-Yoku, forest bathing, and forest therapy, where environmental exposure is frequently combined with intentional attention, physical movement, contemplative activities, social interaction, and professional facilitation.

In previous conceptual work concerning the modalities of forest engagement, Guziak (2026) proposed that spending time in forests may be understood across a continuum of experiences differing in intention, structure, depth, continuity, and personal meaning. Individuals may encounter forests through incidental exposure, everyday recreation, contemplative practice, professionally guided sessions, or formally designed nature-based interventions. Although these modalities may overlap substantially, they raise different questions concerning the relationships among environmental conditions, individual responses, professional facilitation, and therapeutic outcomes.

The present section critically examines the scientific literature through this broader perspective. Rather than assuming that forests possess a single identifiable therapeutic mechanism, it considers the possibility that health-related outcomes emerge through interactions among environmental conditions, physiological regulation, attention, perception, emotional processes, behaviour, social relationships, and personal meaning. Particular attention is given to the distinction between effects that may arise through relatively ordinary environmental exposure and those potentially introduced or modified through conscious engagement and professional guidance.

5.2. Environmental Psychology: Theories of Restorative Environments

Two influential theoretical approaches have contributed substantially to the scientific understanding of restorative environments: Attention Restoration Theory (ART) and Stress Recovery Theory (SRT). Although both frameworks address potentially beneficial responses to natural environments, they emphasise different psychological and physiological processes and should not be regarded as interchangeable explanations.

Attention Restoration Theory, developed by Kaplan and colleagues, proposes that particular environments may facilitate recovery from fatigue associated with sustained directed attention. Directed attention is involved in activities requiring individuals to maintain concentration, inhibit distractions, and deliberately organise cognitive resources. Although these processes are essential for everyday functioning, prolonged demands may contribute to attentional fatigue and reduced cognitive performance.

Kaplan (1995) identified four environmental qualities associated with restorative experiences: being away, fascination, extent, and compatibility. Being away refers to the experience of psychological distance from ordinary demands; fascination describes environmental features that attract attention without requiring substantial deliberate effort; extent concerns the coherence and scope of an environment that allows individuals to experience immersion; and compatibility refers to the relationship between environmental opportunities and an individual’s purposes, needs, and capacities. According to this framework, restoration is facilitated when environmental characteristics allow directed-attention resources to recover while attention remains engaged in less demanding ways.

The concept of soft fascination is particularly relevant to forest environments. Observing moving leaves, shifting patterns of sunlight, flowing water, or distant landscapes may attract attention without imposing the sustained cognitive demands associated with complex tasks. Importantly, this theoretical perspective does not require individuals to undertake a formally organised activity. Rather, the restorative potential of a natural environment may arise partly through its characteristics and the relationship between those characteristics and an individual’s existing attentional demands.

Experimental findings reported by Berman et al. (2008) provide support for this perspective. Their research compared interactions with natural and urban environments and found improvements in selected measures of directed attention following nature exposure. Related benefits were observed in an experimental condition involving natural images. These findings are relevant because they suggest that certain cognitive benefits may arise through environmental exposure without requiring professionally guided therapeutic activities. Nevertheless, the results should not be interpreted as demonstrating that all natural environments consistently restore attention or that every cognitive function responds similarly.

The restorative qualities proposed by ART are also dependent upon individual circumstances. A forest characterised by unfamiliar sounds, difficult terrain, dense vegetation, or uncertain navigation may demand substantial directed attention, particularly when an individual is concerned about safety. Environmental features that are restorative for one person may therefore be distracting, demanding, or uncomfortable for another. The potential for restoration is not determined exclusively by the presence of vegetation but also by the relationship between environmental conditions and the person experiencing them.

Stress Recovery Theory provides a complementary explanation by focusing more directly on affective appraisal and physiological responses to environmental conditions. Ulrich et al. (1991) investigated emotional and physiological responses to natural and urban scenes following exposure to a stressful experience. Their findings suggested that particular natural environments may facilitate relatively rapid stress-related recovery, as reflected in physiological and emotional measures. This framework emphasises the importance of environments perceived as relatively safe, pleasant, and non-threatening.

An earlier contribution by Ulrich (1984) examined postoperative recovery among surgical patients whose hospital rooms provided different window views. Patients whose rooms overlooked natural scenery were reported to have shorter postoperative hospital stays and to receive fewer potent analgesics than matched patients whose windows faced a brick wall. Although the study was small and observational, it became influential because it suggested that environmental characteristics might influence health-related outcomes even when individuals were not intentionally participating in nature-based activities.

The significance of these findings lies partly in their implications for passive environmental exposure. Individuals do not necessarily need to walk through forests, practise mindfulness, or consciously direct attention toward natural elements for aspects of the surrounding environment to influence their experience or physiological functioning. Visual exposure, environmental appraisal, and other sensory processes may contribute to responses without being incorporated into a formal therapeutic protocol.

Nevertheless, neither ART nor SRT establishes that natural environments are universally restorative. Their explanatory value depends upon environmental characteristics, individual perceptions, the outcomes being measured, and the conditions under which exposure occurs. Both frameworks therefore provide important theoretical foundations without resolving all questions concerning the therapeutic effectiveness of forest environments.

Table 5.1. Comparison of Attention Restoration Theory and Stress Recovery Theory

Note. Both theories offer explanatory frameworks rather than evidence that all forests are therapeutic or that professionally guided experiences are necessary to produce restoration.

5.3. Beyond Restoration: Multiple Pathways Linking Nature and Human Health

Although Attention Restoration Theory and Stress Recovery Theory have significantly influenced research on nature and human well-being, the relationship between natural environments and health is unlikely to be adequately explained through either framework alone. Human responses to natural settings involve complex interactions among environmental exposure, physical activity, psychological processes, social relationships, and broader living conditions. Consequently, understanding the potential health-related effects of forests requires consideration of multiple interacting pathways.

Hartig et al. (2014), in their comprehensive review of nature and health, identified several relevant pathways, including air quality, physical activity, social cohesion, and stress reduction. Their analysis demonstrated that natural environments may influence health through both direct and indirect processes. Access to green spaces may encourage walking, recreational participation, and other forms of physical movement, potentially influencing cardiovascular functioning, physical fitness, sleep, and psychological well-being. Natural settings may also provide opportunities for interpersonal contact and community participation, while environmental characteristics such as vegetation, shade, acoustic conditions, and local climate may influence experience independently of deliberate activity.

Kuo (2015) further expanded this discussion by reviewing a wide range of mechanisms potentially connecting nature contact with human health. The review identified 21 possible mechanisms or contributing processes spanning environmental, psychological, physiological, and behavioural domains. It also examined the possibility that improved immune functioning could represent an important connecting pathway. However, this proposed relationship should be understood as a hypothesis concerning interacting mechanisms rather than an established explanation for all observed health benefits.

The significance of these broader approaches is that they challenge the assumption that an observed improvement must originate from one identifiable element of a forest experience. During a relatively ordinary forest visit, an individual may simultaneously engage in physical movement, experience changes in atmospheric and acoustic conditions, direct attention toward the environment, encounter other people, and undergo changes in emotional state. These processes may reinforce, modify, or counteract one another.

For example, a pleasant forest environment may encourage a person to walk for longer than they would in a less appealing setting. A sense of environmental safety may facilitate relaxation, which may influence attentional processes and emotional experience. Social companionship may contribute to feelings of support, while the surrounding environment provides the context within which interaction occurs. Alternatively, difficult terrain, uncomfortable weather, perceived threats, or unwanted social interaction may reduce the potential benefits of the encounter.

The existence of multiple plausible pathways introduces a central methodological challenge. When a study reports improved well-being following a forest visit, it may be difficult to determine whether the change resulted primarily from the environment, physical movement, opportunities for rest, expectations, attentional shifts, social interaction, or the combined influence of these components. Without appropriate comparison conditions, attributing an observed outcome to one specific mechanism remains uncertain.

This complexity becomes particularly relevant in professionally guided Shinrin-Yoku sessions, where environmental exposure is frequently combined with sensory invitations, movement, stillness, contemplation, reflective activities, and group interaction. Evidence concerning the effects of forest exposure must therefore be distinguished from evidence concerning the additional contribution of specific guiding techniques. The observation that a guided session produces beneficial outcomes does not, by itself, establish which components of the experience were responsible.

5.4. Physiological Responses to Forest Environments

The investigation of physiological responses represents one of the most influential contributions to the scientific development of Shinrin-Yoku. Research conducted in Japan, particularly through work associated with Yoshifumi Miyazaki and colleagues, helped establish experimental approaches for comparing human physiological responses under forest and urban environmental conditions.

Park et al. (2010) reported findings from field experiments conducted across 24 forest environments in Japan, involving 280 young male participants. The experimental design included short periods of walking and viewing under forest and urban comparison conditions. The investigators examined physiological indicators including salivary cortisol, blood pressure, pulse rate, and heart rate variability, thereby exploring several dimensions of stress-related physiological regulation.

Compared with the urban conditions, forest environments were associated with lower salivary cortisol concentrations, lower pulse rates, lower blood pressure, increased indicators of parasympathetic nervous system activity, and reduced indicators of sympathetic activity. These findings suggest that relatively brief exposure to selected forest environments may influence physiological processes associated with stress regulation.

The inclusion of both walking and viewing conditions is especially significant in the context of therapeutic attribution. Physiological differences were observed during comparatively simple forms of forest engagement rather than exclusively following elaborate therapeutic exercises. Consequently, the findings support the investigation of forest environments as potential contributors to physiological regulation independently of formal professional facilitation.

However, several limitations must be recognised. The study population consisted of young male participants, which restricts the extent to which the findings can be generalised to women, older adults, children, or individuals with particular health conditions. Furthermore, forest and urban environments differ across numerous environmental characteristics, including vegetation, traffic exposure, noise, air quality, temperature, and other contextual variables. The observed differences therefore cannot be attributed exclusively to vegetation or to any single environmental component.

An additional distinction concerns the interpretation of physiological measurements. Lower blood pressure, pulse rate, or cortisol concentration under particular experimental conditions may indicate short-term physiological differences, but they do not independently establish long-term disease prevention, clinically meaningful recovery, or treatment efficacy. The duration and clinical relevance of these responses require separate investigation.

The contribution of Park et al. (2010) should therefore be understood in relation to the specific question their research addressed. The findings provide experimental evidence that selected forest and urban environments are associated with different short-term physiological responses. They do not establish that every forest environment produces equivalent effects, that all individuals respond similarly, or that professional guidance is necessary for such responses to occur.

5.5. The Autonomic Nervous System, the HPA Axis, and Stress Regulation

Research investigating physiological responses to forest exposure frequently examines the autonomic nervous system and the hypothalamic–pituitary–adrenal (HPA) axis. Both systems participate in the regulation of physiological responses to changing environmental and internal conditions, although their functioning is considerably more complex than a simple distinction between stress and relaxation.

The autonomic nervous system contributes to the regulation of cardiovascular activity, digestion, and numerous other bodily processes. Its sympathetic and parasympathetic divisions are involved in different aspects of physiological regulation, but their activities should not be interpreted as representing universally harmful and beneficial states, respectively. Both contribute to adaptive functioning according to the demands placed upon the organism.

Similarly, the HPA axis plays an important role in responses to stress through the regulation of hormones, including cortisol. Cortisol is involved in energy metabolism, circadian regulation, immune processes, and adaptation to environmental demands. Consequently, lower cortisol concentrations should not automatically be interpreted as indicating better health. The relevance of a particular measurement depends upon factors such as timing, physiological context, baseline conditions, and the purpose of the response.

McEwen (2007) emphasised the central role of stress-related biological systems in adaptation while examining the potential consequences of excessive or prolonged regulatory demands. This perspective is particularly valuable in interpreting forest-bathing research because it discourages simplistic assumptions that a single physiological indicator can adequately represent an individual’s overall state of health or nervous system functioning.

Antonelli et al. (2019) conducted a systematic review and meta-analysis examining salivary cortisol responses associated with forest bathing. The review included 22 studies, eight of which contributed to the quantitative meta-analysis. The pooled findings indicated lower cortisol concentrations under forest conditions compared with urban comparison conditions, suggesting potentially favourable short-term stress-related responses.

However, the review identified important methodological complications. Cortisol concentrations differed between the forest and urban groups even before exposure in the pooled comparisons, complicating the attribution of subsequent differences exclusively to the immediate environmental experience. Such baseline differences may reflect participant characteristics, expectations, prior environmental exposure, or other factors unrelated to the intervention itself. The authors also reported substantial heterogeneity in post-intervention findings, indicating that the effects were not consistent across all included studies.

Heart rate variability is another commonly investigated physiological measure. It provides information about variation in the intervals between consecutive heartbeats and can contribute to the assessment of aspects of autonomic regulation. Nevertheless, heart rate variability is influenced by breathing patterns, posture, physical activity, age, health status, and measurement procedures. Interpretation therefore requires more precision than assuming that an increase necessarily demonstrates improved nervous system balance.

For example, an individual walking slowly through a forest and pausing regularly may display different cardiovascular or autonomic patterns from someone navigating a noisy urban street. These differences may reflect combinations of physical activity, environmental conditions, breathing, psychological appraisal, and attentional demands. Without suitable controls, the contribution of each element cannot be established.

The available findings provide scientific support for investigating the relationship between forest exposure and short-term physiological regulation. However, they do not justify universal claims that forest bathing restores autonomic balance, reduces cortisol in every individual, prevents stress-related illness, or produces comparable outcomes regardless of the conditions of exposure.

5.6. Phytoncides, Forest Atmospheres, and Biological Exposure

The potential biological significance of plant-derived airborne compounds represents another important direction within forest medicine research. As discussed in the preceding historical section, the concept of phytoncides emerged through research associated with Boris P. Tokin and subsequently became relevant to investigations of forest atmospheres and their possible relationships with human physiological functioning.

In contemporary scientific discussions, phytoncides are commonly associated with biologically active volatile compounds emitted by plants, including certain terpenes and related substances. However, forest atmospheres contain complex mixtures of compounds whose concentrations and compositions vary according to tree species, temperature, season, climatic conditions, and ecological characteristics. Their biological and ecological functions include participation in plant defence, chemical signalling, and interactions with other organisms.

Some laboratory investigations have demonstrated biological activities associated with particular plant-derived compounds, while studies within forest medicine have examined whether exposure to forest atmospheres may be related to changes in human immune or stress-related indicators. These different forms of evidence must nevertheless be distinguished because laboratory findings concerning isolated compounds do not necessarily demonstrate equivalent outcomes following ordinary environmental exposure.

Li (2010) reviewed investigations examining the relationship between forest bathing trips and measures of human immune functioning. The studies considered indicators including natural killer cell activity, selected immune cell populations, the expression of immune-related proteins, and urinary adrenaline concentrations. Some findings suggested increased natural killer cell activity following forest visits, with changes observed beyond the immediate exposure period.

These findings contributed to scientific interest in the possibility that forest environments might influence aspects of immune regulation. The investigators also considered potential relationships involving airborne plant-derived compounds and changes in stress-related hormonal activity. However, the interpretation of these findings requires several important qualifications.

First, changes in natural killer cell activity or other immune-related biomarkers do not demonstrate protection against cancer, infectious diseases, or other clinical conditions. Second, some early studies involved relatively small samples and particular exposure circumstances, limiting their generalisability. Third, because forest visits involve simultaneous exposure to multiple environmental and behavioural influences, observed immune-related changes cannot automatically be attributed to phytoncides or any other isolated atmospheric component.

The ecological significance of plant-derived compounds also deserves consideration. These compounds are not produced by trees for the purpose of improving human health; rather, they arise through biological processes involved in the functioning and survival of plants within ecological systems. Their potential influence on human physiology therefore represents one possible consequence of interactions between organisms and environmental conditions.

This distinction has broader implications for how the forest is conceptualised within therapeutic discourse. Scientific evidence may demonstrate biological interactions between human organisms and forest environments without establishing that forests intentionally produce therapeutic outcomes. Biological influence does not require purposeful healing agency.

Equally, the identification of potentially active airborne compounds should not encourage the reduction of forest experience to atmospheric chemistry alone. A forest encounter also includes visual, auditory, tactile, thermal, behavioural, psychological, and relational dimensions that may influence the overall experience. Research concerning phytoncides therefore contributes an important, but incomplete, perspective on the potential health-related effects of forest environments.

5.7. Psychological Outcomes: Mood, Anxiety, Depressive Symptoms, and Emotional Regulation

The psychological effects of forest exposure and nature-based activities have become a substantial focus of contemporary research. Investigations have examined perceived stress, anxiety, depressive symptoms, tension, fatigue, mood, emotional regulation, and related psychological outcomes. Although many studies report favourable findings, their interpretation requires attention to differences in intervention characteristics, participant populations, research designs, outcome measures, and the certainty of the underlying evidence.

Bratman et al. (2015) investigated the psychological and neural responses associated with a 90-minute walk in a natural environment compared with an urban setting. Participants assigned to the natural condition reported reduced rumination and exhibited changes in activity within a brain region implicated in self-referential thought processes. The findings suggested that nature exposure may influence cognitive and emotional processes relevant to psychological well-being. However, changes in rumination or neural activity following a single exposure do not establish that nature contact constitutes an effective treatment for depressive disorders.

Broader evidence concerning structured nature-based interventions was synthesised by Coventry et al. (2021), whose systematic review and meta-analysis included 50 studies. The interventions encompassed gardening, green exercise, and other structured outdoor activities. The review reported improvements in several psychological outcomes, including depressive mood, anxiety, and aspects of positive and negative affect. Nevertheless, the considerable diversity in intervention content, duration, study design, and participant characteristics complicates the identification of common mechanisms.

This distinction is particularly important when evidence from broad nature-based intervention research is used to support claims concerning forest therapy. Although different activities may share exposure to natural environments, their psychological and behavioural components may differ substantially. Improvements observed after gardening, physical exercise, or community-based outdoor activities cannot automatically be attributed to forest environmental exposure alone.

More specifically, Qin et al. (2026) conducted a systematic review and meta-analysis of forest therapy interventions examining psychological stress, depressive symptoms, and anxiety. The review included 25 studies involving 1,876 participants and reported pooled standardised mean differences of approximately −0.71 for stress, −0.68 for depressive symptoms, and −0.77 for anxiety symptoms. These findings suggest potentially meaningful psychological benefits across the included interventions.

However, substantial heterogeneity was identified, with I² values exceeding 74%. The certainty of evidence was rated moderate for psychological stress and low for depressive and anxiety symptoms. Furthermore, the review relied on validated self-report measures rather than establishing corresponding physiological changes across all included participants. The findings therefore support further investigation but should not be interpreted as providing definitive evidence of clinical treatment efficacy.

A second systematic review and meta-analysis published in 2026 illustrates the importance of distinguishing favourable outcomes from confidence in the evidence. Andrade et al. (2026) examined short-term cardiovascular and mental health responses to Shinrin-Yoku across 11 studies. Although the review reported favourable findings for outcomes including heart rate, tension–anxiety, and depressive mood, the overall certainty of evidence was classified as very low, primarily because of risk of bias, inconsistency, and imprecision.

These differences between reviews are scientifically important. Statistically significant pooled findings do not necessarily indicate that the evidence is methodologically robust, clinically meaningful, or sufficiently consistent to justify universal recommendations. Differences in eligibility criteria, outcome measurements, intervention characteristics, and statistical approaches may also contribute to variation among review conclusions.

Table 5.2. Selected Evidence Concerning Psychological Outcomes Following Nature-Based and Forest-Based Activities

Note. These findings concern different interventions, populations, measurements, and levels of evidence certainty. The existence of favourable results does not imply equivalent effectiveness across all forms of forest engagement.

Taken together, the literature supports the potential value of forest-based experiences as complementary approaches to psychological well-being. However, the evidence does not establish that every forest experience produces comparable psychological outcomes, that all reported improvements are clinically significant, or that professionally organised interventions necessarily outperform independent nature engagement. More precise research is needed to determine which components contribute to particular outcomes and under what conditions these effects may persist.

5.8. Everyday Nature Recreation and Mental Health

An important limitation of research focusing primarily on professionally organised forest therapy is that it may overlook the potential significance of ordinary nature engagement. Individuals frequently visit forests, parks, gardens, and other natural environments without defining their activities as therapeutic or participating in structured interventions. Nevertheless, these experiences may still be relevant to psychological functioning and subjective well-being.

Rosa et al. (2025) investigated associations between nature-based recreation and depressive symptoms in a cross-sectional study involving 1,492 adults from the United States, Spain, and Brazil. The study examined different forms of nature-based recreational engagement, including forest activities, gardening, and nature-based adventure. Participants reporting recreational engagement at least monthly generally exhibited fewer depressive symptoms than those participating less frequently.

The investigators also reported that individuals who did not engage in any nature-based recreational activity at least monthly had a 73% higher prevalence of PHQ-9 scores of 10 or greater compared with participants who engaged in such activities at least monthly. This finding suggests a potentially important association between everyday nature recreation and depressive symptom burden.

However, the cross-sectional design does not permit conclusions concerning causality. Individuals experiencing depressive symptoms may have reduced motivation, fewer opportunities, or greater difficulty participating in recreational activities. Conversely, nature-based recreation may contribute to psychological well-being. Both relationships may operate simultaneously, potentially alongside other social, economic, environmental, and behavioural influences.

The significance of the study therefore lies not in demonstrating that ordinary nature recreation treats depression, but in extending the discussion beyond formally organised interventions. It suggests that associations between nature engagement and psychological functioning may also be present within activities undertaken independently and for purposes unrelated to therapy.

This distinction has implications for understanding the contribution of professional guidance. If independent engagement with natural environments is associated with aspects of well-being, it would be inappropriate to assume that the entire therapeutic value of a professionally guided forest experience originates from its structure or facilitator. A guide may introduce additional opportunities for learning, attention, reflection, social interaction, or support, but these contributions must be evaluated in relation to the potential influences already present within the environment and the participant’s own engagement.

5.9. The Forest as a Dynamic and Multisensory Environment

Forest environments provide complex combinations of visual, auditory, olfactory, tactile, thermal, spatial, and other sensory conditions. Vegetation produces changing patterns of form, colour, movement, and contrast, while the surrounding acoustic environment may include birdsong, insects, flowing water, wind, and other biological or physical sounds. Forest atmospheres contain mixtures of airborne compounds, and variations in temperature, humidity, light, terrain, and canopy structure influence bodily and perceptual experience.

These environmental components do not operate in isolation. The experience of hearing birdsong, for example, may be influenced by the surrounding landscape, perceived safety, familiarity with the sound, personal memories, and the presence of competing noises. Similarly, the scent of vegetation may evoke different emotional responses according to cultural associations and previous experiences. The same environmental stimulus may therefore contribute to different experiences among individuals, even when exposure occurs under similar physical conditions.

Forest environments also vary considerably in their ecological characteristics. Dense evergreen forests, open woodlands, subtropical forests, temperate deciduous forests, and urban forest parks may differ in vegetation structure, biodiversity, microclimate, acoustic conditions, accessibility, and levels of human disturbance. Seasonal and weather-related changes introduce further variation, meaning that the same forest may provide substantially different environmental conditions during different periods of the year.

Consequently, the expression forest exposure does not identify one uniform environmental experience. Two studies may classify their interventions as forest bathing while exposing participants to environments that differ substantially in ecological characteristics, sensory conditions, and environmental demands. These differences may influence outcomes, although their relative contributions often remain insufficiently investigated.

This variability complicates attempts to establish standardised relationships between forest exposure and particular health outcomes. Unlike a precisely controlled clinical substance, a forest cannot be administered under identical environmental conditions across all individuals and settings. The forest is a dynamic ecological environment within which human biological, psychological, behavioural, and social processes unfold.

Recognising environmental variability does not diminish the potential value of forests for human well-being. Rather, it encourages more accurate descriptions of environmental conditions and greater attention to the possibility that different settings support different forms of experience. The scientific challenge is to investigate the characteristics and combinations of conditions associated with particular outcomes without assuming that all forests possess equivalent therapeutic properties.

5.10. Sensory Reception, Conscious Attention, and the Meaning of Sensory Engagement

The expression engaging the senses is frequently used in Shinrin-Yoku and forest therapy education. Guides may invite participants to listen to surrounding sounds, observe changes in light, feel different textures, become aware of the surrounding air, or attend to bodily sensations while walking or remaining still. Such invitations are commonly intended to encourage a more attentive relationship with the environment.

However, the terminology requires conceptual clarification. Human sensory systems continuously receive and process information from the external environment and the body itself. Vision, hearing, olfaction, touch, proprioception, vestibular perception, and interoception contribute to ongoing perception and physiological regulation. These processes do not begin when individuals consciously direct attention toward them.

A person sitting quietly in a forest continues to receive auditory, visual, thermal, and other sensory information even when attention is occupied by thoughts, memories, or concerns. Environmental conditions may also influence physiological processes without becoming the primary object of conscious awareness. Variations in ambient temperature, for example, may contribute to thermoregulatory responses without deliberate observation, while auditory information may continue to be processed when attention is directed elsewhere.

This does not imply that every stimulus produces a significant physiological effect or that non-conscious processing necessarily leads to therapeutic outcomes. Rather, it establishes that sensory reception, conscious attention, and therapeutic response are different processes that should not be treated as equivalent.

A guided sensory invitation therefore does not activate sensory systems that were previously inactive. Instead, it may influence the direction, duration, selectivity, and interpretation of attention. For example, a participant may hear birdsong without deliberately attending to it, subsequently focus consciously on the sound following an invitation, and then experience a memory or emotional association related to it. Although these processes may occur in close succession, they represent distinguishable dimensions of human experience.

Table 5.3. Distinguishing Sensory Reception, Conscious Attention, Interpretation, and Emotional Response

Note. These processes may interact continuously. The table distinguishes their conceptual roles rather than suggesting a fixed or universal sequence.

The distinction between sensory reception and conscious attention has particular relevance to claims concerning the mechanisms of forest bathing. If environmental conditions can influence certain physiological processes without deliberate attentional activity, then the effects of forest exposure cannot automatically be attributed to structured sensory exercises. At the same time, conscious attention may contribute additional experiential dimensions, including greater awareness of environmental detail, opportunities for contemplation, emotional recognition, and changes in personal meaning.

The relevant scientific question is therefore not merely whether sensory invitations can be beneficial, but whether they produce outcomes that differ from, extend beyond, or interact with those associated with environmental exposure alone. This question requires appropriate comparison conditions and clear distinctions between physiological, psychological, and experiential outcomes. It remains insufficiently resolved across the full range of outcomes commonly associated with Shinrin-Yoku.

5.11. Nature Contact and Nature Connectedness: Related but Distinct Concepts

Another important distinction concerns the relationship between exposure to natural environments and the development of nature connectedness. Although these concepts are frequently discussed together, they refer to different dimensions of human relationships with the natural world.

Nature contact broadly describes exposure to, or interaction with, natural environments and elements. It may involve walking through forests, observing vegetation, gardening, spending time in parks, or encountering natural features within everyday surroundings. Nature connectedness, by contrast, concerns an individual’s perceived relationship with nature, including emotional affiliation, identity, meaning, and a sense of belonging.

These dimensions may influence one another, but they are not interchangeable. An individual may spend considerable time outdoors without developing a strong emotional relationship with the natural world. Conversely, someone with limited opportunities to visit forests may experience substantial nature connectedness through memories, cultural traditions, gardening, observation, or relationships with particular places and organisms.

Lumber et al. (2017) identified contact, emotion, meaning, compassion, and beauty as important pathways associated with the development of nature connectedness. Their findings suggest that the quality and character of engagement may be relevant alongside the frequency or duration of nature contact. Consequently, approaches that encourage emotional engagement, recognition of beauty, reflection, and personal meaning may contribute to aspects of connectedness that are not necessarily captured by measurements of environmental exposure alone.

This perspective is particularly relevant to professionally guided Shinrin-Yoku sessions, which may intentionally provide opportunities for participants to observe environmental details, reflect upon emotional responses, and explore their perceived relationship with nature. However, such processes are not exclusive to professional guidance. Individuals may experience meaningful encounters spontaneously, develop attachments to familiar places through repeated visits, or cultivate nature connectedness through independent contemplative practices.

The distinction also has implications for research examining physiological restoration. A brief forest visit may be associated with favourable changes in stress-related indicators without necessarily producing a lasting increase in nature connectedness. Conversely, an individual may maintain a profound relationship with a particular forest while experiencing discomfort, sadness, or heightened alertness during certain visits.

Physiological restoration and nature connectedness should therefore be treated as related but distinct potential outcomes. Neither can be assumed to demonstrate the other, and their relationship requires investigation rather than conceptual equivalence.

5.12. Horizontal and Vertical Dimensions of Forest Engagement

Building upon the distinction between nature contact and nature connectedness, Guziak (2026) proposed horizontal and vertical dimensions of forest engagement as a conceptual framework for examining differences in continuity and subjective experience. This distinction is intended as a heuristic model for organising inquiry rather than an established physiological classification or validated measure of therapeutic effectiveness.

The horizontal dimension concerns the frequency, continuity, and integration of forest engagement into everyday life. It includes how often individuals visit natural environments, whether access is available throughout ordinary routines, and how patterns of contact develop over time. Repeated exposure may create opportunities for physical movement, familiarity, environmental learning, and the development of habitual relationships with particular places.

The vertical dimension concerns the perceived depth and quality of an encounter, including conscious attention, contemplation, emotional engagement, personal meaning, and nature connectedness. An experience may become subjectively significant through reflection, perceived beauty, memory, curiosity, or an altered sense of relationship with the surrounding environment.

These dimensions may interact, but neither necessarily determines the other. An individual may visit a forest every day while primarily engaging in physical exercise or practical activities, whereas another person may experience a deeply meaningful encounter during a relatively brief visit. Both forms of engagement may be valuable, but the nature of their possible contributions differs.

Regular forest contact may provide repeated opportunities for movement, environmental exposure, and psychological respite. A subjectively meaningful encounter may contribute to emotional reflection, personal interpretation, or a developing relationship with nature. However, it would be scientifically premature to assume that greater subjective depth necessarily produces larger physiological benefits or that frequent exposure always generates stronger nature connectedness.

The distinction is therefore relevant partly because it allows different outcomes to be examined without establishing a hierarchy of experiences. Some physiological responses may occur following relatively brief exposure under particular environmental conditions. Other outcomes, including place attachment, enduring nature connectedness, and patterns of self-directed engagement, may develop through repeated experiences and personal significance.

This framework also generates questions concerning professional guidance. A guide may support a participant in approaching a familiar environment differently, developing confidence, or exploring personal meaning without necessarily producing stronger immediate physiological changes than an independent visit. Similarly, repeated unguided visits may contribute substantially to an individual’s relationship with nature without requiring structured intervention.

The relationship between the horizontal and vertical dimensions remains an empirical question. Their conceptual value lies in encouraging researchers and practitioners to distinguish frequency of contact from perceived depth of experience, while recognising that different patterns of engagement may be associated with different forms of well-being.

5.13. Guided and Unguided Forest Experiences: What Does Guidance Change?

The distinction between guided and unguided forest engagement is central to understanding the additional contribution of professional facilitation. If certain psychological and physiological responses may arise during independent forest exposure, it becomes necessary to investigate whether guidance produces different outcomes, influences different experiential processes, or primarily modifies how participants encounter the environment.

Kim and Shin (2021) compared guided and self-guided forest therapy experiences among 37 university students. Through analysis of participants’ written reflections, the researchers identified both shared sensory themes and differences in the character of reported experiences. Participants in the self-guided condition more frequently described introspective experiences, whereas those in the guided condition more frequently reported emotional changes and social interaction.

These findings suggest that guidance may influence particular experiential dimensions of forest engagement. A professionally facilitated session may direct attention toward selected activities, create opportunities for group interaction, or encourage forms of emotional reflection that differ from those emerging during independent visits. However, because the study relied on written reflections, it did not establish that guided experiences produced superior physiological responses or clinical outcomes.

Zhang et al. (2026) conducted a pilot study comparing therapist-guided forest bathing, unguided forest exposure, and an urban outdoor comparison activity among graduate students in Beijing. The study examined changes in emotional states following three-hour outdoor experiences. Forest conditions generally demonstrated favourable patterns relative to the urban comparison condition, but the investigators did not identify a statistically significant additional short-term emotional benefit associated with therapist-guided exposure compared with unguided forest exposure.

The final analysis included only 26 participants, and the findings must therefore be interpreted as preliminary. Importantly, a statistically nonsignificant difference does not establish equivalence between the interventions or demonstrate that guidance has no additional value. Small samples may lack the statistical power required to detect differences, and the selected measurements may not adequately capture all potentially relevant contributions of professional facilitation.

Nevertheless, the study raises an important question concerning assumptions frequently encountered within forest therapy discourse. The presence of professional structure should not automatically be interpreted as evidence that an experience produces greater therapeutic effects than independent engagement. Whether additional benefits occur depends upon the outcomes measured, the characteristics of participants, the activities introduced, and the nature of the comparison condition.

Professional guidance may contribute through environmental preparation, safety assessment, accessibility, informed participation, attentional invitations, reflective opportunities, social interaction, and support for individuals unfamiliar with forest environments. Conversely, unguided experiences may allow greater autonomy, spontaneous exploration, independent contemplation, and flexibility in pacing.

These potential contributions are not mutually exclusive, nor do they establish that one modality is universally preferable. The value of guidance may depend upon individual needs, circumstances, preferences, and intended outcomes. For some participants, facilitation may increase confidence or support accessibility. For others, self-directed engagement may provide greater freedom and a stronger sense of personal agency.

Research concerning guided and unguided experiences therefore needs to move beyond a simple comparison of which approach is more effective. It should investigate what professional guidance changes, for whom those changes may be relevant, and whether they produce measurable differences in physiological, psychological, experiential, relational, or longer-term outcomes.

5.14. The Forest, the Participant, and the Problem of Therapeutic Attribution

The evidence reviewed throughout this section demonstrates the difficulty of attributing therapeutic outcomes to a single element of forest engagement. Human experiences in forests arise through interactions among environmental conditions, biological processes, attention, emotion, physical activity, social context, personal history, and interpretation. Although these influences may be distinguished conceptually, they often remain closely interconnected within lived experience.

Consider an individual who enters a forest feeling mentally fatigued, begins walking, observes surrounding vegetation, becomes absorbed in thought, pauses to watch a bird, and subsequently experiences a change in emotional state. The change may be associated with physical movement, environmental conditions, an opportunity for rest, an attentional shift, a personal association, or several interacting processes. Without an appropriate experimental design, it is difficult to determine their relative contributions.

Professionally guided experiences introduce additional elements. A guide may select a route, assess environmental risks, establish expectations, provide information, introduce invitations, coordinate group activities, or encourage reflection. Participants may respond differently to the same activity, however, because their experiences are influenced by individual circumstances and personal histories.

A particular natural sound may evoke calm in one participant while producing discomfort in another. A period of silence may encourage introspection for one individual but increase self-consciousness or anxiety for someone else. A guide may respond by adapting an activity, altering its duration, or providing additional support, thereby further modifying the conditions of the encounter.

Consequently, the therapeutic character of a guided forest experience cannot be understood exclusively through the environment or exclusively through professional facilitation. The forest provides environmental conditions; the participant contributes biological responsiveness, perception, behaviour, interpretation, and personal history; the guide contributes preparation and facilitation; and other participants may influence the experience through their presence and social interaction.

At the same time, acknowledging the role of the environment does not require assigning intentional therapeutic agency to the forest. Forests do not assess individual health needs, establish clinical objectives, select interventions, or deliberately regulate human physiology. They contain environmental conditions within which human biological and psychological processes may occur.

Likewise, the presence of a professional guide does not establish that every beneficial process within a session originates from professional intervention. A facilitator may create opportunities for particular forms of engagement, but the participant’s physiological responses, attentional processes, emotional experiences, and interpretations remain integral to the encounter.

A relational understanding of therapeutic experience therefore does not imply that causal attribution is impossible or that every contributing component is equally influential. Rather, it recognises that different elements may operate together and that their relative contributions require systematic investigation.

This perspective also calls for conceptual precision in the use of the term therapeutic. An experience may be perceived as meaningful, calming, restorative, or supportive of well-being without necessarily constituting a clinically validated treatment. The subjective therapeutic significance of an encounter and its demonstrated clinical efficacy represent different forms of evidence and should not be conflated.

5.15. Methodological Limitations and the Interpretation of Forest Therapy Research

Despite substantial growth in forest-related health research, several methodological challenges continue to limit the strength and generalisability of conclusions. These limitations do not invalidate the field, but they require careful interpretation of reported findings and greater precision in the design of future studies.

One central challenge concerns intervention heterogeneity. Studies described as forest bathing or forest therapy may investigate short walks, seated viewing, guided sensory activities, contemplative practices, multi-day forest visits, or repeated programmes extending across several weeks. These activities may differ substantially in duration, physical demands, professional involvement, social interaction, and intended outcomes. Consequently, combining their findings under a single intervention category may obscure important differences.

Environmental heterogeneity introduces another challenge. Forest settings vary in vegetation, biodiversity, temperature, humidity, acoustic characteristics, air quality, terrain, accessibility, and levels of human disturbance. Comparisons between forest and urban environments may therefore involve numerous simultaneous differences, making it difficult to isolate the influence of specific environmental components.

Participant characteristics also affect interpretation. Age, health status, previous nature experience, cultural background, expectations, sensory preferences, and familiarity with particular environments may influence responses. Research involving relatively healthy university students cannot automatically be generalised to individuals experiencing chronic illness, older adults, children, or populations with different environmental circumstances.

A further limitation concerns the duration of observation. Many studies measure physiological or psychological outcomes immediately before and after relatively short experiences. Although such measurements may identify acute changes, they do not establish whether effects persist, whether repeated participation produces cumulative benefits, or whether observed differences translate into improved long-term functioning.

Blinding is also particularly difficult in environmental research. Participants generally recognise whether they are visiting a forest or an urban location, and expectations concerning the benefits of nature may influence their responses, particularly when outcomes rely on self-report measures. Such expectations do not necessarily invalidate a finding, but they complicate causal interpretation and require suitable methodological consideration.

Perhaps most importantly, forest-based studies frequently combine several potentially influential components. Walking, rest, sensory exposure, professional facilitation, meditation, and social interaction may occur simultaneously. Unless comparison conditions are designed to isolate particular elements, it remains uncertain which components contributed to the observed outcome.

Table 5.4. Major Methodological Challenges in Forest Therapy Research and Their Implications

These limitations also highlight the need to distinguish several levels of scientific inference. Evidence that forest exposure is associated with improved well-being is not equivalent to evidence that the environment caused the improvement. Evidence of a short-term physiological change does not necessarily demonstrate a clinically meaningful outcome. Similarly, evidence that a guided programme is followed by favourable changes does not establish that professional guidance was the component responsible.

Future research would benefit from designs capable of comparing guided forest experiences, unguided forest exposure, appropriate non-forest activities, and different combinations of attentional or social components. Such comparisons may help clarify whether professional facilitation contributes additional effects, whether those effects depend upon participant characteristics, and whether differences are evident in physiological measurements, psychological outcomes, subjective meaning, or longer-term patterns of engagement.

Greater methodological precision should not be understood as an attempt to reduce the complexity of forest experience to isolated variables alone. Rather, it provides a means of investigating which aspects of a complex encounter contribute to particular outcomes while recognising that experimental findings may not fully capture its experiential richness.

5.16. From Forest Exposure to Everyday Health and Public Access

The significance of research concerning forests and human health extends beyond the development of professionally organised interventions. If certain natural environments may support aspects of psychological and physiological well-being through ordinary forms of exposure, then questions concerning accessibility, environmental quality, and opportunities for everyday contact become central.

White et al. (2019) analysed data from 19,806 adults in England and reported that spending at least 120 minutes per week in nature was associated with a greater likelihood of reporting good health and high well-being. Although this finding attracted considerable attention, the observational design does not establish causality or demonstrate that 120 minutes represents a universally effective threshold. The association may reflect interacting influences involving individual characteristics, lifestyle, environmental access, and other circumstances.

Nevertheless, the study contributes to a broader understanding of nature contact as a potentially relevant component of everyday living conditions. Forests, parks, gardens, and other green environments may provide opportunities for physical activity, solitude, social interaction, attentional restoration, and meaningful engagement without necessarily requiring formal therapeutic organisation.

An individual may develop a routine of visiting a familiar park, walking through nearby woodland, sitting beneath a tree, or observing seasonal changes. These activities may be undertaken for recreation, curiosity, companionship, contemplation, or personal enjoyment rather than for an explicitly therapeutic purpose. Their potential contribution to well-being does not necessarily depend upon professional supervision.

However, access to natural environments is not equally distributed. Geographical location, financial resources, transport availability, mobility, environmental safety, working conditions, and the accessibility of suitable spaces may influence opportunities for regular nature contact. Consequently, the potential contribution of forests to population-level health cannot be considered independently of social and environmental inequalities.

Professional and community-based programmes may help address some barriers by providing information, accessible activities, organised opportunities, or supportive social environments. Their contribution may be particularly relevant for individuals who feel uncertain about entering unfamiliar natural settings or who benefit from assistance in participating safely.

Nevertheless, improving access to nature should not be understood exclusively through the expansion of therapeutic services. Urban planning, environmental protection, public transport, accessible pathways, community education, and the preservation of local green spaces may also play essential roles in supporting opportunities for engagement.

This raises an important question concerning the future direction of forest therapy and related practices. If ordinary nature contact may contribute to aspects of well-being, should the development of the field focus exclusively on refining professionally guided programmes, or should it also contribute to creating conditions in which more people can establish meaningful and sustained relationships with natural environments?

These objectives are not mutually exclusive, but they reflect different approaches. One emphasises professional organisation and the investigation of specific interventions, while the other addresses the broader environmental and social conditions that enable nature engagement to become part of everyday life.

5.17. Synthesis: What Does the Evidence Ultimately Establish?

The scientific literature reviewed in this section provides credible support for the proposition that certain natural and forest environments may contribute to aspects of human psychological and physiological functioning. Experimental studies have identified differences between selected forest and urban conditions, including changes in attention, perceived stress, mood, and physiological indicators associated with stress regulation. Systematic reviews and meta-analyses have also reported favourable psychological outcomes following forest-based and broader nature-based interventions, although the magnitude, consistency, methodological quality, and certainty of evidence vary considerably.

These findings are important, but they do not establish that all forests are uniformly therapeutic or that every individual experiences equivalent benefits. Neither do they demonstrate that short-term improvements necessarily translate into long-term clinical outcomes. The evidence is more appropriately understood as supporting the investigation of forests as environments containing multiple conditions that may contribute to human well-being under particular circumstances.

A central implication of the reviewed research is that therapeutic outcomes cannot be adequately explained through a single environmental mechanism. Physiological regulation, attentional processes, emotional appraisal, physical activity, sensory exposure, social relationships, and personal meaning may all contribute to an individual’s experience. Their relative importance may vary according to environmental conditions, participant characteristics, previous experiences, and the purpose of the encounter.

The relationship between sensory reception and conscious attention deserves particular emphasis. Individuals do not need to consciously notice every environmental stimulus for their sensory and physiological systems to respond to surrounding conditions. Likewise, a structured sensory invitation is not necessary for an individual to encounter the sounds, light, temperature, and atmosphere of a forest. Nevertheless, deliberate attention may influence how environmental information is perceived, interpreted, remembered, and integrated into personal experience.

These physiological and experiential dimensions are related, but they are not identical. A forest environment may contribute to particular short-term physiological responses without producing profound subjective meaning, while a deeply meaningful experience may occur without measurable improvement in selected physiological indicators. Neither possibility invalidates the other; rather, both demonstrate the importance of defining outcomes precisely.

The contribution of professional guidance must be considered within this broader context. A guide may support safety, accessibility, attentional exploration, emotional reflection, social participation, and the development of confidence or connectedness. However, these contributions should not be confused with the environmental and biological processes that may also occur during independent forest engagement. Evidence demonstrating favourable outcomes following guided sessions cannot, by itself, establish that the effects originated primarily from the guide or the structure of the intervention.

At the same time, the available comparisons between guided and unguided experiences remain too limited to support universal conclusions concerning their relative effectiveness. The absence of statistically significant differences in small studies does not demonstrate that guidance is ineffective, just as positive outcomes following guided activities do not establish its additional efficacy. More rigorous comparisons are needed to examine which contributions guidance may introduce, which participants may benefit, and which outcomes are most relevant.

The distinction between therapeutic potential and clinical efficacy is equally important. Forest experiences may be restorative, emotionally meaningful, or supportive of subjective well-being without constituting clinically validated treatments. The designation of an experience as therapy does not itself establish its effectiveness, just as the absence of therapeutic terminology does not prevent individuals from experiencing meaningful or beneficial changes.

A forest is not a clinical practitioner and does not possess an intention to treat human illness. It is a dynamic ecological environment containing physical, biological, and sensory conditions that may influence human functioning. The participant contributes through biological responsiveness, perception, behaviour, interpretation, and personal history. A professional guide, when present, may contribute through preparation, facilitation, and the creation of opportunities for particular forms of engagement. Other participants may influence the experience through interpersonal relationships and shared activity.

From this perspective, the therapeutic character of a forest encounter may be better understood as an emerging property of relationships among environmental conditions, human processes, and context rather than as an effect belonging exclusively to one component.

This interpretation does not deny the possibility of identifying specific causal mechanisms. Rather, it recognises that the presence of multiple interacting elements requires more precise investigation before particular effects can be attributed to a forest characteristic, a participant’s activity, or a professional intervention.

The conceptual distinction introduced through the horizontal and vertical dimensions of forest engagement further broadens this inquiry. Repeated contact with nature and the subjective depth of individual encounters may contribute to different dimensions of human well-being. Neither should automatically be regarded as superior, and their relationships with physiological and psychological outcomes remain open to empirical investigation.

For research, the challenge is therefore to distinguish the effects of environmental exposure from those associated with physical activity, conscious attention, emotional interpretation, social interaction, and professional facilitation. For practitioners, the challenge is to recognise both the potential contribution of the environment and the limits of professional influence, while maintaining ethical responsibility and sensitivity to individual differences.

Perhaps the forest does not become therapeutic simply because an encounter with it is professionally organised. Rather, professional organisation may represent one among several ways through which human beings access, experience, and interpret the potential influences of natural environments.

This proposition leaves an important question unresolved. If an individual experiences physiological restoration while sitting quietly beneath a tree, should the therapeutic contribution be attributed primarily to the forest, the individual’s biological capacity for regulation, the circumstances allowing rest, or the relationship among these elements? Furthermore, when a guide introduces an invitation to observe the same tree, does the invitation generate an additional therapeutic effect, or does it modify the participant’s attention, interpretation, and subsequent experience of processes that were already occurring?

The available evidence does not yet provide a universal answer to these questions. Their significance lies in revealing why forest therapy cannot be adequately understood through professional structure, environmental exposure, or subjective experience alone.

A more comprehensive understanding recognises that forests may offer opportunities for physiological regulation, psychological restoration, personal connection, and meaning through multiple forms of engagement. Some responses may arise through relatively passive exposure, while others may involve conscious attention, physical movement, social relationships, or sustained personal involvement. Professional guidance may support particular pathways, but it does not possess exclusive authority over the potential benefits of nature engagement.

The forest may contribute to human well-being without being called therapy, just as an individual may experience something meaningful in nature without seeking a therapeutic outcome.

Recognising this possibility does not diminish the scientific importance of Shinrin-Yoku research or the potential contribution of professional practice. Instead, it broadens the questions that both research and practice must be willing to examine.

The discussion therefore extends beyond whether forests can produce beneficial effects toward a more complex consideration of which environmental, biological, psychological, behavioural, and relational processes contribute to those effects, under what circumstances they occur, and how professionally organised experiences may influence an encounter that remains fundamentally relational.

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