Abstract
Background: Ecotherapy — an umbrella term encompassing forest therapy, horticultural therapy, green and blue care, wilderness and adventure therapy, green exercise, and nature-based interventions — has grown from a marginal therapeutic curiosity into a mainstream public-health discourse over the last four decades. However, the conceptual diffusion of these modalities and the parallel diversification of the health outcomes attributed to them have not been mapped in a unified chronological framework.
Objective: To provide a chronological evidence-mapping of (a) how ecotherapy concepts have evolved from 1980 to 2026 and (b) how the spectrum of measured health outcomes has broadened across four discernible historical periods.
Methods: A Web of Science search retrieved 999 candidate records spanning 1980–2026. After multi-stage cleaning — Article-only filter, restriction to SCI-EXPANDED and ESCI indexes, 53 health-relevant WoS subject categories, topic-level relevance screening with a 26-term regular-expression pattern, and a targeted false-positive sweep that removed pharmaceutical methylene/Prussian/indigo blue dye studies and insurance-funded works misclassified through “Blue Care Network” organisational naming — a clean corpus of 942 records was retained. Four periods were defined by natural break-points in publication density: Pioneering Era (1980–2006, n = 13), Early Consolidation (2007–2013, n = 77), Expansion (2014–2019, n = 266), and Pandemic-Era Surge (2020–2026, n = 586).
Findings: Outcome attention shifted progressively from physiological end-points (sympathetic activity, blood glucose, blood pressure, natural killer cell activity) toward composite mental-health and quality-of-life constructs, with mental-health prevalence in abstracts rising from 15.4% in the Pioneering Era to 38.4% in the Pandemic-Era Surge. The umbrella term “nature-based intervention” superseded earlier modality-specific labels, appearing in 28.8% of recent abstracts compared with none before 2007. Methodological maturation was visible: randomised controlled trials rose from 0% (Pioneering) to 10.6% (Pandemic-Era), and systematic reviews from 0% to 3.9%, while eco-anxiety and climate-grief emerged as novel outcomes (0.9% of the most recent period).
Conclusions: The chronological trajectory of ecotherapy reflects a coherent four-stage maturation: physiological discovery, mechanistic consolidation, public-health expansion, and pandemic-accelerated institutional integration. The outcome agenda has paralleled this evolution but remains uneven in its coverage of severe psychiatric illness, dose–response specification, and long-term durability of effects.
Keywords: ecotherapy; nature-based intervention; forest therapy; shinrin-yoku; horticultural therapy; green exercise; bibliometric review; chronological evidence mapping; health outcomes.
1. Introduction
The proposition that contact with nature improves health is among the most enduring intuitions in Western medical thought, yet its translation into formal therapeutic modalities is comparatively recent. Over the past four decades a heterogeneous family of practices — sometimes branded as ecotherapy, sometimes as forest therapy, horticultural therapy, healing garden design, care farming, green exercise, blue care, wilderness or adventure therapy — has crystallised into a recognised, if still loosely federated, intervention class (Pretty et al., 2005; Shanahan et al., 2019). What unites these modalities is the deliberate use of natural environments or biotic elements as the active ingredient of treatment, in contradistinction to incidental exposure during ordinary recreation. What divides them is the diversity of theoretical grounding, target populations, delivery formats, and, most consequentially for this review, the spectrum of health outcomes through which their effects are measured.
Two intertwined questions follow from this heterogeneity. First, how has the conceptual architecture of ecotherapy evolved over time, and through which terminological and modality-specific vocabularies has it been articulated in successive periods? Second, how has the catalogue of health outcomes attributed to these modalities expanded, contracted or shifted as the field has matured? Although individual modalities such as shinrin-yoku have received bibliometric attention in their own right, the family-level chronological architecture and the parallel evolution of measured outcomes have not previously been mapped in a unified framework. The present analysis addresses this gap through a chronological evidence-mapping of a curated bibliometric corpus.
Two complementary findings motivate the structure of what follows. The first is that publication volume traces a clear four-stage trajectory, with natural break-points around 2007, 2014 and 2020 that segment the literature into a Pioneering Era, an Early Consolidation phase, an Expansion phase, and a Pandemic-Era Surge. The second is that each of these periods exhibits a distinctive outcome signature: physiological mechanisms dominate the early decades, mental-health and quality-of-life constructs come to dominate the most recent, and novel constructs such as eco-anxiety and climate grief emerge only in the final period. Reading the literature chronologically therefore illuminates not only what ecotherapy has come to mean, but also which dimensions of human health the field has progressively claimed jurisdiction over.
2. Methodological Approach
A Web of Science Core Collection search was conducted using the topic operator with twenty-six terms covering the principal ecotherapy lexicon: ecotherapy and eco-therapy, nature therapy and nature-based or nature-assisted therapy, green therapy, green care, forest therapy, forest bathing, shinrin-yoku, wilderness therapy, adventure therapy, outdoor therapy, horticultural therapy, garden therapy, therapeutic horticulture, healing gardens, therapeutic gardens, care farming, social farming, green exercise, blue therapy, blue care, and nature-based or nature-assisted interventions. Document type was restricted to Article, with book chapters, proceedings papers, data papers and retracted publications excluded. Web of Science index inclusion was restricted to the Science Citation Index Expanded (SCI-EXPANDED) and the Emerging Sources Citation Index (ESCI), and the search was further constrained to fifty-three health-relevant Web of Science subject categories ranging from Public, Environmental and Occupational Health and Psychology subfields through Rehabilitation, Geriatrics, Nursing, Oncology and Critical Care Medicine.
The raw retrieval comprised 999 records, which were subjected to a multi-stage cleaning protocol. A first pass removed ten records whose titles, abstracts and keyword fields contained none of the twenty-six ecotherapy lexical anchors despite category-level inclusion — for example, studies of migrant farmworker health services, hospital outsourcing and antibiotic stewardship in pneumonia. A second pass removed two duplicate records identified through DOI matching and title-year soft matching. A third, methodologically critical pass eliminated 45 systematic false positives produced by the lexical pattern itself: twenty-two pharmaceutical or toxicological case reports of methylene blue therapy for methemoglobinemia, three records on Prussian blue and indigo blue chemical treatments, seventeen Blue Cross Blue Shield of Michigan / Blue Care Network insurance-funded clinical studies, two Dutch primary-care ‘Blue Care’ integrated-care program studies that bear no relationship to ecotherapy, and one Queensland ‘Blue Care’ nursing organisational study. The final corpus comprised 942 unique articles, with a cumulative citation count of 21,727 according to the Web of Science Core Collection.
Four chronological periods were defined by inspection of cumulative publication curves, with break-points placed at the years where annual output discretely shifted regime. Health outcomes were operationalised through a twenty-two-category taxonomy applied via regular expression matching against titles, abstracts, author keywords and Keywords Plus fields. Therapy types were identified through an eleven-category pattern set covering the major modality labels. Study designs were classified through nine descriptors including randomised controlled trials, systematic reviews and meta-analyses, cohort, case-control, qualitative, scoping review, pre-post, cross-sectional and laboratory experimental designs. All percentages reported below refer to the proportion of period-specific abstracts in which at least one descriptor from the relevant category was detected. The corpus and analytical pipeline are reproducible in full from the supplementary Excel file.
3. The Pioneering Era (1980–2006): Scattered Modalities and the Birth of an Outcome Vocabulary
The Pioneering Era contained only thirteen indexed articles across twenty-seven calendar years, with average annual output below 0.5. Yet the period is conceptually formative because it contains the first articulations of three distinct intellectual currents that would later coalesce: the Japanese physiological tradition of shinrin-yoku, the Anglophone wilderness and adventure therapy tradition focused on adolescent and oncology populations, and the British green-exercise paradigm focused on combined mental and physical outcomes. Although the volume is modest, the period accounts for a cumulative 1,466 citations, an average of 112.8 per article, reflecting the foundational status these works have attained. Notably, the highest-cited paper of the entire corpus — Pretty, Peacock, Sellens and Griffin’s The Mental and Physical Health Outcomes of Green Exercise — appears in this period, with 749 citations (Pretty et al., 2005). This work is conceptually pivotal because it explicitly conjoined mental and physical outcomes as a single research object, framing what would become the dominant outcome architecture of the field.
Outcomes attended to in the Pioneering Era were dominated by stress and cortisol measures (30.8% of abstracts), recovery and rehabilitation framings (30.8%), pediatric and adolescent populations (30.8%), and older-adult contexts (30.8%). Cognitive outcomes appeared in 23.1% of abstracts. Ohtsuka, Yabunaka and Takayama’s (1998) demonstration that shinrin-yoku reduced blood glucose in diabetic patients introduced metabolic end-points; this was followed by Yamaguchi, Deguchi and Miyazaki (2006), who demonstrated that exercise in forest environments altered sympathetic nervous activity relative to urban exercise. The mechanistic linchpin of the period is Li and colleagues’ (2006) identification of phytoncides — volatile compounds emitted by trees — as inducers of human natural killer cell activity, an observation that would underwrite a decade of subsequent immunological research. Adventure therapy entered the literature with Jelalian and colleagues’ (2006) cognitive-behavioural pediatric obesity trial. Methodologically the period was modest: no randomised controlled trials, no systematic reviews, and roughly a quarter of articles relied on qualitative approaches, with the remainder predominantly observational or laboratory-based.
Two features of the Pioneering Era foreshadow later debates. First, the wilderness and adventure therapy literature was disproportionately concerned with vulnerable youth and oncological populations — Stevens and colleagues’ (2004) adventure therapy programme for adolescent cancer patients and Elad and colleagues’ (2003) jeep-trip study with young adult cancer survivors are exemplars. Second, the early Japanese forest medicine work focused on autonomic and immune mechanisms, prefiguring the eventual rapprochement of psychological and physiological outcomes in subsequent periods. The structural absence of evidence synthesis (no systematic reviews and only sporadic narrative ones) meant that the conceptual scaffolding of the field was being laid one primary study at a time, without yet a hierarchical evidence architecture.
4. Early Consolidation (2007–2013): The Forest Medicine Programme and the First Synthesis
Between 2007 and 2013 the field grew nearly six-fold, producing 77 articles with a cumulative 4,396 citations. The defining intellectual achievement of this period was the methodical empirical consolidation of forest therapy and shinrin-yoku as physiologically grounded interventions, primarily through programmatic Japanese research and parallel Korean and Chinese work. Forest therapy or forest bathing appeared in 19.5% of the period’s abstracts, and the first international synthesis — Bowler, Buyung-Ali, Knight and Pullin’s (2010) BMC Public Health systematic review with 396 citations — established the field’s first authoritative summary of evidence for the added health benefits of natural-environment exposure. The methodological inflection is unmistakable: the share of cohort designs rose to 6.5%, the first randomised controlled trials appeared (3.9% of abstracts), and the first systematic review proportion reached 1.3%.
The outcome agenda diversified substantially. Anxiety entered the vocabulary in 15.6% of period abstracts where it had been absent in the Pioneering Era. Stress and cortisol remained central at 33.8%, but mental-health framings rose to 20.8% and quality-of-life or wellbeing to 29.9%. The cardiovascular branch of the literature matured rapidly: Lee and colleagues’ (2011) controlled study of forest bathing in young Japanese males demonstrated parasympathetic activation and sympathetic attenuation, attracting 395 citations; Mao and colleagues (2012) showed therapeutic effects of forest bathing on hypertension in older adults; and Sung, Woo, Kim, Lim and Chung (2012) integrated cognitive-behavioural therapy with forest exposure to demonstrate concomitant reductions in blood pressure, salivary cortisol and improvements in quality of life among hypertensive elderly patients. The immune-system literature reached an inflection in this period with Li and colleagues’ two 2008 papers showing that forest visits increase natural killer cell activity and anti-cancer protein expression in both general adult (Li, Morimoto, Kobayashi, Inagaki, Katsumata, Hirata, Hirata, Suzuki, Li, Wakayama, et al., 2008a) and female (Li, Morimoto, Kobayashi, Inagaki, Katsumata, Hirata, Hirata, Shimizu, Li, Wakayama, et al., 2008b) samples.
Horticultural therapy and therapeutic gardens emerged as a distinct strand alongside forest medicine, accounting for 23.4% of period abstracts. Gonzalez, Hartig, Patil, Martinsen and Kirkevold’s (2010) prospective study of therapeutic horticulture for clinical depression in the Journal of Advanced Nursing is the period’s most cited horticultural work, foregrounding active components rather than mere garden exposure. Morita and colleagues’ (2007) characterisation of psychological effects of forest environments on healthy adults established shinrin-yoku as a stress-reduction technique transferable to non-clinical populations. Cumulatively, the Early Consolidation period transformed the field from one in which ecotherapy was a heterodox curiosity into one in which forest therapy in particular could be discussed in mainstream public-health journals with formal evidence architecture, including the first hypertension trials and the first systematic synthesis. Yet the population scope remained relatively narrow: predominantly healthy adult volunteers in laboratory or short-trip settings, with patient populations only beginning to enter.
5. Expansion (2014–2019): Cardiovascular Consolidation and the Rise of Nature-Based Intervention as Umbrella Term
The Expansion period contained 266 articles, accounting for 28.2% of the entire corpus and a further 3.5-fold increase in annual output. Cumulative citations reached 10,413, with a peak average of 39.1 citations per article. The defining conceptual move of the period was the gradual consolidation of the umbrella term “nature-based intervention” — appearing in 11.7% of period abstracts compared with 3.9% in the Early Consolidation phase — as a way to unite modalities that had previously been described in modality-specific vocabularies. Shanahan and colleagues’ (2019) integrative paper on Nature-Based Interventions for improving health and wellbeing, which canvasses purposes, target populations and outcomes, exemplifies this terminological consolidation and accumulated 248 citations within five years of publication. The period therefore marks the transition from a federation of named modalities to a recognisable intervention class with a shared label.
The outcome agenda widened further. Mental-health framings rose to 25.2% of abstracts, quality-of-life and wellbeing to 31.6%, mood to 17.7%, and heart-rate variability and related cardiovascular measures to 14.7%. The cardiovascular branch entered its empirical apex with three high-impact studies: Lee and colleagues’ (2014) demonstration of forest therapy effects on cardiovascular relaxation in young adults; Ochiai and colleagues’ (2015) investigation of physiological and psychological effects of forest therapy in middle-aged males with high-normal blood pressure; and Takayama and colleagues’ (2014) characterisation of emotional, restorative and vitalising effects across four Japanese forest sites. Green exercise expanded sharply to 18.8% of abstracts, signalling that the Pretty et al. (2005) paradigm had become a major research stream in its own right. Public-health framings consolidated through narrative reviews such as Haluza, Schönbauer and Cervinka’s (2014) synthesis on the physiological effects of outdoor nature.
The Expansion period also saw the literature begin to engage with urban planning and population-level mental health. Vujcic and colleagues’ (2017) work on nature-based solutions for improving mental health in urban areas, published in Environmental Research, exemplifies a shift from individual-level therapy to environment-level intervention design. Russo and Cirella’s (2018) examination of how much greenery modern compact cities require — invoking healing-garden design as a public-health architectural principle — illustrates the same trend. Among university student populations, Holt and colleagues (2019) distinguished active from passive use of green space in relation to health and wellbeing, foreshadowing the dose-response questions that would dominate the subsequent period. Methodologically, scoping reviews appeared for the first time (1.5% of abstracts), with Moeller, King, Burr, Gibbs and Gomersall’s (2018) scoping review of nature-based interventions in institutional and organisational settings illustrating the field’s growing engagement with implementation science. Randomised controlled trials remained at 3.0% of period output, suggesting that the methodological hierarchy was still climbing but not yet dominated by experimental evidence.
Two further trends merit emphasis. Wilderness and adventure therapy, which had been disproportionately represented in the Pioneering Era at 30.8% of abstracts, declined to 12.0% of period abstracts, suggesting partial displacement by other modalities or relabelling within the new nature-based intervention vocabulary. The pediatric and adolescent share also contracted from 18.2% (Early Consolidation) to 13.9% (Expansion), reflecting a broader pivot toward adult and especially older-adult populations, the latter rising to 28.9% of period abstracts. The cancer-population focus contracted markedly from the Pioneering Era’s 15.4% to 4.1% in Expansion, indicating that oncology, having served as an early entry point for adventure therapy, was no longer the dominant clinical anchor; mental health had assumed that role.
6. The Pandemic-Era Surge (2020–2026): Mental-Health Centrality, Methodological Maturation, and the Emergence of Eco-Anxiety
The Pandemic-Era Surge contains 586 articles — 62.2% of the entire corpus — with a still-accumulating citation total of 5,452 at the time of analysis. Annual output reached 112 in 2025, more than double the highest annual output of the Expansion period. Three structural shifts define the period. First, the umbrella term “nature-based intervention” became unambiguously dominant, appearing in 28.8% of abstracts and overtaking forest therapy and horticultural therapy as the most prevalent therapy descriptor in the literature. Second, mental health rose to 38.4% of abstracts and quality-of-life and wellbeing to 46.6%, making them the most prevalent outcome categories overall. Third, methodological hierarchy climbed materially: randomised controlled trials reached 10.6% of abstracts (a three-fold increase over Expansion), systematic reviews and meta-analyses reached 3.9%, and scoping reviews 2.4%.
The pandemic functioned as both context and catalyst. COVID-related framings appeared in 7.8% of period abstracts, with no precedent in earlier periods. Robinson, Brindley, Cameron, MacCarthy and Jorgensen’s (2021) geospatial and socioecological study of nature’s role in supporting health during the COVID-19 pandemic, with 102 citations, became the most cited paper of the period. Zabini and colleagues (2020) compared the restorative effects of forest and urban videos during lockdown, an investigation that would not have been imaginable in earlier periods both methodologically and motivationally. Robinson, Jorgensen, Cameron and Brindley (2020) introduced the concept of green prescribing in the United Kingdom, signalling the institutionalisation of nature-based interventions within primary care. Rogerson, Wood, Pretty, Schoenmakers, Bloomfield and Barton (2020) explicitly framed the question of dose, examining the efficacy of regular doses of green exercise for mental wellbeing — a dose-response framing that the Expansion period had begun to anticipate.
Patient-population reach extended substantially. Bielinis, Jaroszewska, Lukowski and Takayama (2020) examined the effects of a forest therapy programme on mental hospital patients with affective and psychotic disorders, taking the modality into severe-psychiatric-illness territory; psychiatric severity descriptors accordingly rose to 8.0% of period abstracts. Serrat and colleagues (2020) reported a pragmatic randomised controlled trial of a multicomponent fibromyalgia treatment (NAT-FM) combining pain neuroscience education, exercise therapy, cognitive-behavioural therapy and nature exposure, demonstrating how nature components are increasingly integrated within multimodal chronic-pain interventions. Mechanistic refinement continued, exemplified by Shin and colleagues’ (2020) demonstration of neuroprotective effects of limonene — a forest-emitted terpene — against amyloid-beta neurotoxicity in a Drosophila model of Alzheimer’s disease, an investigation that traces the Li (2006) phytoncide programme into translational neurobiology.
The emergence of eco-anxiety as a measured outcome is a distinctive feature of the period. Climate-anxiety and eco-anxiety constructs appeared in 0.9% of abstracts — small in proportional terms but unprecedented in earlier periods, where such constructs were absent. Gunasiri and colleagues’ (2022) study of hope, coping and eco-anxiety in young people in a climate-impacted Australia exemplifies this emergent outcome. The conceptual implication is that nature-based interventions are no longer evaluated solely as remedies for individual psychophysiological distress but also as responses to collective-scale environmental affect. Older-adult populations rose to 37.5% of abstracts, reflecting a steady gerontological orientation, while sleep outcomes rose to 5.6% from 2.6% in earlier periods, indicating the entry of sleep medicine as a partner discipline.
Despite this expansion, two methodological caveats apply. First, the average citation count per article declined sharply to 9.3 — a reflection of the brief citation window for the most recent works rather than diminished impact, but a feature that complicates direct cross-period comparison. Second, although the proportion of randomised controlled trials climbed to 10.6%, qualitative designs remained the most prevalent identifiable methodology at 28.5%, suggesting that despite headline methodological advances, the field’s evidentiary base is still mixed in character and substantially descriptive.
7. Cross-Period Synthesis: How the Outcome Lens Tracked the Concept
Reading the four periods in sequence reveals a coherent four-stage trajectory in which conceptual evolution and outcome diversification advanced in tandem rather than independently. In the Pioneering Era, the field consisted of isolated outposts — Japanese forest medicine, Anglo-Saxon wilderness therapy, British green exercise — each with distinct theoretical anchors and physiological end-points. The outcomes attended to were correspondingly disjointed: blood glucose in diabetic patients (Ohtsuka et al., 1998), sympathetic activity in healthy adults (Yamaguchi et al., 2006), natural killer cell activity (Li et al., 2006), and obesity in adolescents (Jelalian et al., 2006). Quality-of-life and mental-health framings, although present in 30.8% and 15.4% of period abstracts respectively, were not yet the integrative architectural backbone of the field.
The Early Consolidation phase saw the field acquire a recognisable empirical core in forest medicine and a recognisable methodological core in observational and early experimental studies. Outcomes consolidated around stress and cortisol, the cardiovascular system (blood pressure, heart-rate variability), and the immune system (natural killer cell activity), with mental-health framings rising into the 20% range. Crucially, this is the period in which anxiety enters the corpus as a measurable outcome (15.6%), where it had been entirely absent before. The first systematic review — Bowler et al. (2010) — establishes the field’s first authoritative claim to public-health relevance, which would underwrite subsequent expansion.
The Expansion period reorganised the field around the umbrella concept of nature-based intervention and the integrated mental–physical outcome architecture that had been foreshadowed by Pretty et al. (2005). The cardiovascular branch reached its empirical apex; mood, attention restoration, and quality-of-life constructs proliferated; and the geographic reach of the literature widened beyond Japan, Korea and the United Kingdom. Methodologically, scoping reviews entered the toolkit and the discipline began to engage with implementation science (Moeller et al., 2018). Patient populations remained predominantly non-clinical, but the seeds of severe-psychiatric-illness work, oncology re-entry and dose-response inquiry were sown.
The Pandemic-Era Surge accelerated all of these trends while introducing two genuinely novel features: pandemic-context restoration research and eco-anxiety as a treatment outcome. Green prescribing emerged as a translational pathway into primary care (Robinson et al., 2020). Severe-psychiatric-illness applications became visible (Bielinis et al., 2020). Multimodal RCTs integrating nature exposure with established psychological therapies came online (Serrat et al., 2020). Mechanistic research entered translational neuroscience (Shin et al., 2020). Cumulatively, the most recent period demonstrates that the field has moved from a federation of modalities defending individual claims to a recognisable intervention class engaging systematically with mainstream public-health, clinical, and planetary-health agendas. The accompanying outcome lens has correspondingly broadened from discrete physiological end-points to composite mental-health and quality-of-life constructs and, most recently, to collective-scale environmental affect.
Table 1 synthesises the chronological pattern by reporting the proportion of each period’s abstracts in which selected outcome and therapy descriptors were detected.
| Indicator | D1 (1980–2006) | D2 (2007–2013) | D3 (2014–2019) | D4 (2020–2026) |
| Number of articles (n) | 13 | 77 | 266 | 586 |
| Cumulative WoS citations | 1,466 | 4,396 | 10,413 | 5,452 |
| Mean citations / article | 112.8 | 57.1 | 39.1 | 9.3 |
| Forest therapy / shinrin-yoku (%) | 23.1 | 19.5 | 21.8 | 24.2 |
| Horticultural therapy (%) | 7.7 | 23.4 | 17.7 | 16.6 |
| Wilderness / adventure (%) | 30.8 | 18.2 | 12.0 | 7.5 |
| Green exercise (%) | 7.7 | 3.9 | 18.8 | 10.4 |
| Nature-based intervention (%) | 0.0 | 3.9 | 11.7 | 28.8 |
| Mental health general (%) | 15.4 | 20.8 | 25.2 | 38.4 |
| Depression (%) | 15.4 | 16.9 | 16.5 | 24.4 |
| Anxiety (%) | 0.0 | 15.6 | 14.7 | 20.5 |
| Stress / cortisol (%) | 30.8 | 33.8 | 35.7 | 35.7 |
| Cardiovascular HR/HRV (%) | 0.0 | 5.2 | 14.7 | 8.7 |
| Quality of life / wellbeing (%) | 30.8 | 29.9 | 31.6 | 46.6 |
| COVID / pandemic (%) | 0.0 | 0.0 | 0.0 | 7.8 |
| Eco-anxiety / climate (%) | 0.0 | 0.0 | 0.0 | 0.9 |
| RCT design (%) | 0.0 | 3.9 | 3.0 | 10.6 |
| Systematic review / meta-analysis (%) | 0.0 | 1.3 | 0.8 | 3.9 |
Note. Percentages refer to the proportion of each period’s articles in which the descriptor was detected in title, abstract, author keywords or Keywords Plus. Multiple descriptors may co-occur within a single article. Source: authors’ bibliometric analysis of 942 WoS records.
8. Discussion: Mature Domains, Persistent Gaps, and the Reorganising Pandemic
Three mature evidence domains emerge from the chronological synthesis. The first is the cardiovascular branch, which reached empirical critical mass in the Expansion period through forest-therapy studies of blood-pressure and heart-rate variability and was independently corroborated through hypertension-specific trials in the Early Consolidation phase. Practitioners and policy-makers seeking evidence for cardiovascular indications of forest therapy can draw on a coherent multi-decade record. The second is the stress and cortisol branch, which is the most stable outcome family across periods (30.8% to 35.7% prevalence with minimal variance), suggesting that physiological stress reduction is the field’s most durable claim. The third is the depression and mood branch, which has grown steadily from 15.4% in the Pioneering Era to 24.4% in the Pandemic-Era Surge, supported by foundational therapeutic-horticulture work (Gonzalez et al., 2010) and increasingly by green-exercise trials (Rogerson et al., 2020).
Equally instructive are the persistent gaps. Severe psychiatric illness, despite the Bielinis et al. (2020) demonstration of forest therapy benefits in affective and psychotic disorders, remains the subject of only 8.0% of Pandemic-Era abstracts and a comparable share earlier — a striking under-representation given that depression, anxiety and stress reduction dominate the outcome agenda. The clinical translation pathway from mild distress to severe illness is therefore incomplete. Dose-response specification, although now an explicit research target as in Rogerson et al. (2020), remains underdeveloped across the corpus. Long-term durability of effects is rarely studied, with cross-sectional and pre-post designs continuing to outnumber longitudinal observational and trial follow-up designs. The pediatric and adolescent population, prominent in the Pioneering Era largely through adventure therapy, has declined to 14.3% of Pandemic-Era abstracts, raising the question of whether developmental life-course considerations have been adequately retained.
The pandemic period also revealed a structural reorganisation of the field’s institutional position. Green prescribing in the United Kingdom (Robinson et al., 2020) signals an institutional pathway into the National Health Service that did not exist when Pretty et al. (2005) inaugurated the green exercise paradigm. Eco-anxiety (Gunasiri et al., 2022) signals a new outcome jurisdiction at the planetary-health intersection — one that traditional clinical trial designs may struggle to accommodate. These developments suggest that the next stage in the field’s evolution may be characterised less by the discovery of new outcomes and more by the integration of established outcomes within delivery systems, payment structures, and population-level prescribing pathways.
9. Conclusion
The chronological evidence-mapping of 942 SCI-Expanded and ESCI articles indicates that ecotherapy has matured through four discernible periods, with conceptual and outcome evolution proceeding in parallel rather than independently. The Pioneering Era established three foundational modalities and an outcome vocabulary anchored in stress, cognition and pediatric oncology. The Early Consolidation phase produced the field’s first authoritative synthesis and codified forest therapy as a physiologically grounded intervention with cardiovascular, immune and stress outcomes. The Expansion phase introduced the umbrella term nature-based intervention, took the cardiovascular branch to its empirical apex, and broadened the outcome lens to mood, attention and quality of life. The Pandemic-Era Surge accelerated mental-health and quality-of-life centrality, introduced randomised controlled trials and systematic reviews at materially higher proportions, established green prescribing as a translational pathway, and added eco-anxiety as a novel outcome. Reading the field chronologically reveals not only what ecotherapy has become but also which dimensions of human health it has progressively claimed jurisdiction over, and where the unfinished business of clinical translation, dose specification and severe-illness extension still lies.
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