Next Article in Journal
Structure and Function of Urban Forests and Green Spaces in a Changing World
Previous Article in Journal
Alien vs. Native—Influence of Fallow Deer (Dama dama) Introduction on the Native Roe Deer (Capreolus capreolus) Population
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Forests
Volume 15
Issue 6
10.3390/f15061013
forests-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Review

Progress and Prospects of Research on the Impact of Forest Therapy on Mental Health: A Bibliometric Analysis

by
Ruoyu Wan
1,
Ruohong Wan
2 and
Quan Qiu
3,*
1
School of Architecture and Urban Planning, Huazhong University of Science and Technology, Wuhan 430074, China
2
Academy of Art & Design, Tsinghua University, Beijing 100084, China
3
College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou 510642, China
*
Author to whom correspondence should be addressed.
Forests 2024, 15(6), 1013; https://doi.org/10.3390/f15061013
Submission received: 12 May 2024 / Revised: 3 June 2024 / Accepted: 6 June 2024 / Published: 11 June 2024
(This article belongs to the Section Forest Economics, Policy, and Social Science)
Browse Figures
Review Reports Versions Notes

Abstract

:
This study aims to assess the global progress in research on the impact of forest therapy on mental health by using bibliometric analysis. We analyzed the relevant literature from the Web of Science Core Collection (WoSCC) database by utilizing software tools such as Bibliometrix (Version 4.1), VOSviewer (Version 1.6.19), and CiteSpace (Version 6.3.R1). There appears to be a growing trend in annual publication volumes from 2006 to 2023. Miyazaki was identified as the most prolific author in this field. Japan and South Korea lead in research contributions, while China has the highest number of publications. The International Journal of Environmental Research and Public Health is the journal with the most publications and citations in this area. Recent keyword clustering reveals an increasing frequency of studies on anxiety and urban green spaces. Research findings suggest that exposure to negative air ions and compounds released by plants can stimulate the five human senses, reduce cortisol levels, and improve mental health. Although studies have demonstrated significant effects of forest therapy in alleviating stress, anxiety, and depression, more large-scale and long-term studies are needed for further evidence. Additionally, it is crucial to explore the impact of different forest types, terrains, altitudes, climates, and air conditions on the effectiveness of forest therapy on mental health.

1. Introduction

Forest therapy was coined in 1982 as a healing practice in Japan and has gradually made its way into Japanese clinical fields [1,2]. This holistic practice, celebrated for its capacity to improve human physiological and psychological health and well-being, involves the mindful engagement of the five senses while unwinding in natural settings [3,4,5]. Empirical findings regarding the physiological and psychological impacts of forest therapy include decreased blood pressure and heart rate, alterations in heart rate variability, enhanced immune function, heightened parasympathetic nervous system activity, reduced cortisol levels, alleviation of symptoms related to depression and emotional stress, and an overall increase in subjective feelings of happiness and joy [4,6,7]. While it has been established that physiological relaxation is more pronounced under combined stimuli [8], simultaneous improvements can also be observed in mood disorders, stress levels, and mental relaxation [9]. This underscores the importance of investigating the role of forest therapy in psychological healing.
Forest therapy programs typically incorporate various activities promoting relaxation and well-being, with the goal of integrating and harmonizing humans with the forest environment [9]. This therapy method has gained global recognition as an effective means of addressing psychological disorders, such as improving negative emotions (e.g., low mood, pessimism, and anxiety), alleviating mental stress, and relieving attention fatigue. It employs diverse techniques, including breathing exercises, walking, hiking, yoga, and meditation, as well as guided nature walks and recreational activities like cooking [10,11,12], which are all conducted in forest environments in order to foster a harmonious connection between individuals and nature [13]. These curated activities are designed to cultivate a sense of calm and rejuvenation amidst the natural surroundings.
Given the pervasive impact of civilization-related illnesses on individuals’ daily lives, especially in high-income nations, chronic stress and sedentary lifestyles are increasingly implicated in prevalent civilization diseases [14]. There is a growing recognition that excessive screen time is positively correlated with depression [15], highlighting the escalating prominence of mental health issues among the population. Extensive research suggests that prolonged stress can significantly and detrimentally affect health outcomes [16]. While numerous studies have researched the impact of forest therapy on mental health issues and several literature reviews have been conducted in recent years, most of them mainly focus on outcomes related to physical health [17]. Furthermore, these reviews have predominantly adopted a qualitative approach which relies heavily on subjective judgment and expertise, making quantitative analysis challenging [9,18].
To bridge this divide, this paper endeavors to undertake comprehensive qualitative and quantitative analyses of the research landscape concerning the impact of forest therapy on mental health issues by using CiteSpace, Bibliometrix, and VOSviewer software. The major goals of this research are threefold: (1) analyze the temporal characteristics of publications in this field both quantitatively and qualitatively; (2) examine the current landscape of authorship, institutional affiliations, country contributions, and collaborative networks within the literature; and (3) pinpoint research hotspots and predict future development trajectories in this field. The results of this study seek to offer an objective and comprehensive understanding of the research domain and future directions of forest psychological therapy. This, in turn, will help scholars and policymakers gain insights into the current status and depth of research in this area. Furthermore, the findings can serve as a valuable reference for future research and policy formulation, thus facilitating the continued advancement of this field.

2. Materials and Methods

2.1. Data Source

The data used for analysis were obtained from the Web of Science Core Collection (WoSCC) database, comprising 345 articles retrieved on 20 March 2024. The search string was (TS = (“forest therapy” OR “forest bathing” OR “nature healing” OR “shinrin-yoku” OR “nature basen” OR “forest basen”)) AND TS = (Psychological health OR mental health OR depression OR “mental depression” OR “major depressive disorder” OR “mood disorder” OR “bipolar disorder” OR “seasonal depression” OR psychology* OR “psychotic disorder” OR psychology relaxation OR anxiety OR “anxiety disorder” OR “panic” OR “panic disorder” OR stress OR anger). The time span of the data was from 1 January 2006 to 31 December 2023, with all document types selected. Repetitive and irrelevant articles (including those related to forest tourism planning and forest plant restoration) were filtered out. In the end, a total of 243 pertinent original articles were retained and exported in plain text files in “Full Record and Cited References” format. This dataset can be employed for literature measurement and bibliometric analysis purposes.

2.2. Data Analysis Methods

Bibliometric analysis, a widely utilized and rigorous approach for investigating extensive scientific datasets, entails both the qualitative and quantitative examination of published papers [19]. It analyzes social and structural connections among various research elements such as authors, institutions, countries, journals, keywords, and topics by employing data mining, information processing, and visualization methods [20,21,22]. This approach is crucial to quantitatively evaluating the present state and forecasting emerging trends in disciplines like commerce, management, medicine, and agronomy [23], offering valuable insights into publication patterns, citation trends, and research impact [21,24]. Web visualization software, notably Bibliometrix, plays a crucial role in bibliometric analysis and in facilitating statistical analysis [25,26]. Methods within bibliometric analysis are typically categorized into performance analysis and scientific mapping. Despite a significant volume of related research, few bibliometric studies have focused on the impact of forest therapy on mental health. Therefore, a thorough quantitative and qualitative examination using bibliometric methods offers a more accurate evaluation. This study utilizes bibliometric techniques to statistically analyze and describe research findings on the effects of forest therapy on mental health. The goal is to clarify the current state of work, identify prevalent trends, highlight recent advancements and outline future development trajectories.
For our study, we selected three key tools: (i) VOSviewer (version 1.6.19) (accessible at https://www.vosviewer.com/, accessed on 15 March 2024) serves as graphical user interface software designed for co-citation and co-author analysis [27] (accessed on 12 March 2024). (ii) CiteSpace (version 6.3.R1) (accessible at https://citespace.podia.com/, accessed on 15 March 2024) is a Java-based tool that provides cluster and timeline views [28,29] (accessed on 12 March 2024). (iii) Bibliometrix R-package (version 4.1) (available at https://www.bibliometrix.org, accessed on 15 March 2024) is open-source software developed in R, supporting recommended workflows for bibliometric analysis and enabling comprehensive scientific mapping analyses [30,31].
In this research paper, our objective is to elucidate the correlation between the impact of forest therapy and mental health-related publications spanning the past eighteen years. Additionally, we try to conduct a comprehensive analysis of the present status and trajectory of this field of study. First, we imported the data into Bibliometrix software to analyze the annual trends of the number of articles and citations from 2006 to 2023 and used Excel 2019 for data analysis of the tables. Then, we utilized VOSviewer and Citespace software to analyze the collaboration networks of authors, institutions, countries, and co-citations. Finally, we employed CiteSpace and Bibliometrix to conduct keyword co-occurrence clustering, thematic evolution analysis, and burst term analysis to identify research hotspots and trends in the field of the impact of forest therapy on mental health. The specific process is illustrated in Figure 1.

3. Results

3.1. Overall Trend of Publications and Citations

According to Figure 2, from 2006 to 2023, the number of articles on the mental health effects of forest therapy generally increased, except for 2008 and 2010. This period can be divided into three phases based on the quantity of publications and their rate of increase: the budding phase (2006–2011), the steady ascent phase (2012–2017), and the rapid growth phase (2018–2023). (i) Budding phase: There was only a modicum amount of research in this field, and the annual growth rate of paper quantity was slow. In 2007 and 2011, the average annual number of citations reached its highest point, indicating that the field was receiving more attention. (ii) Steady ascent phase: There was a steady increase in publications, except in 2016, and the average citation rate was 8.7, lower than in the previous phase. (iii) Rapid growth phase: In 2019, the number of publications increased significantly to 33. In the following years, this high quantity was maintained, but the citation rate obviously decreased.

3.2. Author Collaborative Network Analysis

According to the Price formula, the core authors contributing to the effects of forest therapy on mental health were identified. The author collaboration network consists of 300 nodes and 520 links (Figure 3). However, the limited frequency and extent of connections among authors suggest that collaboration among scholars in this research area is not extensive. Seven prolific authors, namely, Yoshifumi Miyazaki (Chiba University), Kagawa, Takashi (Chiba University), Harumi Ikei (Chiba University), Chorong Song (Chungbuk National University), Takayama Morimasa (Tokyo Cardiovascular Care Unit Network Science Communication), Ernest Bielinis (University of Warmia and Mazury), and Qing Li (Nippon Medical School), form large nodes, reflecting their prominent contributions to research on the effects of forest therapy on mental health. The majority of authors engaged in active collaboration from 2017 to 2021. Furthermore, recent years have witnessed a notable surge in the number of authors contributing to research in this field.
Table 1 reveals that Y. Miyazaki stands out as the leading author, with a publication count of 27 and an impressive total citation count of 2315, accompanied by an h-index of 20. The h-index is a composite quantitative indicator used to assess both the quantity and quality of a researcher’s academic output. It is defined as the following: If a person has N papers that have been cited at least N times each in their entire body of academic publications, then their h-index is N. Furthermore, Y. Miyazaki’s earliest research findings date back to 2006. T. Kagawa emerges with the highest average citations per article, with 18 publications garnering a total of 2465 citations. The h-index of the participating authors varied from 6 to 20.

3.3. Analysis of Contribution of Institutions and Countries

The top 10 institutions with the most publications on the impact of forest therapy on mental health from 2006 to 2023 were identified (Figure 4). Institutions from Japan and South Korea accounted for 17.70% of the total number of papers. The Forestry and Forest Products Research Institute in Japan emerged as the most active research institution in this field, with 34 papers, accounting for 10.29% of the total. Other institutions with significant publication output include Chiba University (26 papers, 7.41%), Nippon Medical School (12 papers, 4.94%), Chungnam National University (11 papers, 4.53%), and Chungbuk National University (11 papers, 4.53%). All three leading institutions originate in Japan and exhibit notable total citation counts and centrality, underscoring Japan’s robust focus on studying the impact of forest therapy on mental health and the substantial academic impact of their publications.
The country collaboration map (Figure 5) illustrates the global distribution of publications and collaborations among countries/regions. The shading of colors on the map signifies the number of publications per country, with darker colors indicating higher publication counts. Moreover, the thickness of the lines connecting countries indicates the strength of their collaborative ties, with thicker lines signifying stronger partnerships. Japan has the most connections with South Korea, with a cooperation frequency of 11, followed by Japan and Poland, with a frequency of 6; China and the United States rank third, with a frequency of 5.
Additionally, according to Figure A1 in Appendix A, by observing the color of the nodes, it is evident that Germany, Japan, and South Korea began this research as early as the 1980s, establishing a mature system and scale by the early 21st century. Notably, nodes surrounded by purple rings in the network represent countries with significant influence and centrality, including China, South Korea, the United States, Australia, Germany, Italy, and Spain. Since 2016, China has experienced rapid development in this field due to the promulgation of policies.
Not only does Japan hold an advantage in the count of publications (42), but it also exhibits strong academic influence, with a total citation count reaching 2794 and an average article citation of 66.5. China’s quantity of papers is considerable (55), but its intermediary centrality is relatively lower, with an average article citation of only 26.2. This suggests that China should enhance its academic influence by increasing the quality of research on the effects of forest therapy on mental health. Meanwhile, although the United States has a relatively small number of articles (13), its average article citation is notably high, at 52.4, ranking second. This indicates its outstanding academic influence. As shown in Figure 6, over half of the publications from China, Japan, South Korea, and Germany were generated through domestic collaboration, while Poland exhibited the highest rate of multi-country publications, at 63%.

3.4. Co-Citation Analysis of Publications

The term “co-citation” refers to the situation where the same or multiple publications are cited together by other documents. Co-citation analysis involves the systematic research and examination of these co-citation relationships to reveal key topics, research directions, academic influence, and other significant information within a research field.
We applied Bradford’s Law by using Bibliometrix to identify the most active journals in our dataset. This approach helps analyze journal productivity and pinpoint core journals within a specific field. Out of the 79 journals included in this study, 2 are considered core journals. The top five journals identified are International Journal of Environmental Research and Public Health (ISSN: 1660-4601), Forests (ISSN: 1999-4907), Urban Forestry & Urban Greening (ISSN: 1618-8667), Environmental Health and Preventive Medicine (ISSN: 1347-4715), and Frontiers in Psychology (ISSN: 1664-1078), as depicted in Figure 7. Additionally, based on the Figure A2, among the top ten journals, four are related to the natural environment and four are related to mental health care.
Figure 8 illustrates the co-citation network. We established a minimum citation threshold of 45, and 37 out of 3722 sources surpassed this limit. In the visualization, each node symbolizes a journal, with its size indicating the number of citations the journal has garnered. Lines represent co-citation links between journals, and their thickness denotes the intensity of co-citation between the connected journals. Furthermore, the color of each node is based on the cluster to which it belongs. Journals addressing the effects of forest therapy on mental health were divided into four groups according to their citation frequency. These groups are represented by the colors cyan, grass green, blue, and purple, corresponding to the following journals: International Journal of Environmental Research and Public Health (ISSN: 1660-4601), Journal of Environmental Psychology (ISSN: 0272-4944), Urban Forestry & Urban Greening (ISSN: 1618-8667), and PLOS ONE (ISSN: 1932-6203).

3.5. Analysis of Hotspots and Trends

3.5.1. Keyword Co-Occurrence Analysis

Keywords in a paper can reflect its essential content. By utilizing a co-occurrence network graph of keywords, one can explore the frequency and relationships among them, thereby revealing the research hotspots and emerging trends in a particular field. Figure 9 illustrates the results of keyword co-occurrence analysis. Among 1079 keywords, with a minimum occurrence threshold set at 15, 38 keywords met this criterion. The size and links of nodes represent the frequency of keyword occurrences and the strength of their connections, respectively, and thicker lines indicate stronger keyword associations. Keywords can generally be classified into three types: those related to forest environments, such as “shinrin-yoku” (120), “environment” (60), “atmosphere” (40), and “landscape” (29). Shinrin-yoku, also known as ”forest bathing”, is a Japanese practice that involves immersing oneself in a forest environment to promote physical and mental well-being. The second type concerns psychological states, such as “stress” (67) and “depression” (42). The final type pertains to approaches, such as “health” (71), “natural-killer activity” (42), and “blood pressure” (21). As part of the innate immune system, natural-killer cells (NK cells) can directly recognize and kill abnormal cells. Emotional state has a significant impact on the activity of NK cells; people who have suffered from depression for a long time show a reduction in NK cell activity by more than 20%, which significantly decreases their ability to resist tumor cells [32,33].

3.5.2. Research Hotspot Analysis of Psychological Effect of Forest Therapy

The impact of forest therapy on mental health was further explored through keyword clustering by using the Log-Likelihood Ratio (LLR) clustering algorithm in CiteSpace (refer to Figure 10). Cluster analysis provides insights into the knowledge structure and research focus within a subject based on citation relationships [34]. Employing the g-index (k = 10) as the selection criterion, the resulting network comprised 49 clusters from 1298 references (refer to Figure 10). With a network modularity of 0.55 and an average silhouette score of 0.805, the co-citation delineation is clear, indicating a high level of homogeneity within clusters [28]. Clusters were numbered according to size, with the largest being designated as Cluster #0.
As depicted in the figure, the largest cluster is “pulse rate”, followed by “heart rate variability”, attributed to our extensive research on mood through the assessment of participants’ stress levels. These stress levels were evaluated by using two physiological methods, i.e., measuring heart rate and skin conductance levels [35], as well as one psychological method, i.e., employing the Profile of Mood States (POMS) questionnaire [36]. The third largest cluster, Cluster #2, is “urban green space”. As urban life is getting more closely associated with modern humans, urban green spaces have become a significant focus of forest therapy research [37,38,39]. Although similar trends in mental health benefits are observed in forest environments, differences compared with urban environments exist [17]. Research indicates that there are no significant differences in the values of tension–anxiety, depression–dejection, and anger–hostility [13,40].
Thematic analysis is a flexible qualitative method used to explore patterns across data, revealing common themes and aiding the understanding of interconnected aspects of a phenomenon [41]. This method allows us to elucidate the thematic evolution of research in this field over time, as depicted in Figure 11. We delineated the period since the emergence of research on the impact of forest therapy on mental health into three distinct sub-periods based on publication counts and growth rates: (a) 2006–2012, (b) 2013–2018, and (c) 2019–2023. The diagram divides research into four quadrants based on centrality and density, providing a clear visualization of research hotspots. Centrality measures how interconnected a specific topic is with other clusters, while density assesses the cohesion within a cluster, indicating the degree of relatedness among keywords. Each circle on the diagram represents a topic, identified by its most frequently used keyword with the circle’s size corresponding to the frequency of that keyword.
The first quadrant (upper right) illustrates a motor theme, which is both well-established and crucial in the field of the effects of forest therapy on mental health. In contrast, the second quadrant (upper left) shows an isolated theme, indicating a specialized focus with relatively fewer researchers involved. The third quadrant (bottom left) represents an emerging theme, suggesting nascent development or potential decline. This theme’s progression is relatively slow compared with others and requires further development as the field progresses. Finally, the fourth quadrant (bottom right) contains fundamental themes characterized by high centrality and low density. These are important directions for future research that have not yet received sufficient attention.
As shown in Figure 11 and Figure A2, in the first sub-period (2006–2012), the keyword “shinrin-yoku” already appeared, although “Atmosphere” was the main focus of this period, indicating that initial research was primarily concentrated on the environmental and atmospheric aspects of forest therapy.
In the second sub-period (2013–2018), research themes diversified, with emerging themes such as “anxiety”, “air pollution”, “physical activity”, “quality of life”, “forest”, “Japan”, “restoration”, and “health benefits”. The theme “green space” appeared with high centrality, reflecting its relevance to urbanization processes. The inclusion of “Japan” as a theme highlighted the country’s influence in pioneering and researching forest therapy.
In the third sub-period (2019–2023), themes further evolved and specialized. “Shinrin-yoku” appeared prominently, indicating the practice’s global spread and increasing attention. New and evolving themes, such as “dementia”, “health benefits”, “natural-killer activity”, and the continuation of “air pollution”, reflect the field’s growing complexity and the incorporation of broader health aspects. Specifically, the emergence of “Natural-killer activity” suggests a focus on the biological and immunological impacts of forest therapy.
Overall, “shinrin-yoku” has remained a consistently important theme, underscoring its central role in forest therapy and mental health research. The shift from general themes like “atmosphere” to more specific health outcomes (e.g., “dementia” and “natural-killer activity”) indicates the field’s maturation and the drive to link forest therapy with tangible health benefits. The increasing attention to health-related themes such as “quality of life”, “health benefits”, and “natural-killer activity” signifies a deepening understanding of the physiological and psychological benefits of forest therapy.

3.5.3. Frontiers Analysis of Impact of Forest Therapy on Mental Health

Burst terms serve as valuable indicators for anticipating abrupt shifts and emerging trends within a particular field. By analyzing these emerging terms, citation burst detection reveals the dynamic evolution of publications in the field within a specific timeframe, offering insights into the appeal of the information explosion to scholars. Essential metrics such as burst duration, intensity, and timing serve as crucial benchmarks, capturing the essence of this phenomenon. A sudden surge in citations for particular keywords or articles can uncover novel discoveries and directions. This section explores the citation burst detection of keywords and references relevant to research on the effects of forest therapy on mental health. Figure 12 presents the top seven most cited keywords and references, providing insights into the recurring themes and influential works within this domain.

4. Discussion

4.1. Analysis Mental Health of Therapy Programs

Based on the evolving landscape of research concerning the effects of forest therapy on mental health from 2006 to 2023, a comprehensive understanding can be gleaned regarding its historical trajectory, present status, and future prospects. The emergence of studies exploring the impact of forest therapy on mental health dates back to 2006. These investigations not only trace the development of forest therapy but also offer insights into novel research avenues.
Notably, the highest number of citations was in 2014, which was likely related to the establishment of a certification system for forest medicine physicians by the International Society of Nature and Forest Medicine (INFOM) [42]. Since 2015, the number of publications has been rising in a zigzag pattern, peaking in 2023. This increase may be attributed to organizations such as the International Nature and Forest Therapy Alliance (INFTA) and INFOM, as well as the efforts of various governments which raise public awareness of forest therapy as a public health category. These entities have been promoting the concept of forest therapy, setting standards, and conducting research cooperating on a global scale. As of 2015, South Korea had built 167 natural recreation forests. By 2017, Japan had certified 62 forest therapy bases and established a comprehensive forest therapy base certification system, along with strict standards for the training and qualification certification of forest guides and therapists. These efforts provide a solid foundation for the development of forest therapy research.
According to the number of publications and their growth rate, we divided the research history into three sub-periods. (i) Budding phase (2006–2011), with limited research and slow growth in paper quantity: The establishment of the Forest Cultural Ecosystem Services (FCES) concept in 2005 emphasizes the non-material benefits that people gain from ecosystems, including spiritual enrichment, cognitive development, recreation, and aesthetic experiences [43]. This concept has promoted the recognition and research of these benefits. (ii) Steady ascent phase (2012–2017), when the number of publications steadily increased: This increase was closely related to the inclusion of forest healing in forest strategies, management plans, and policies in many countries, such as China and Japan [44,45]. (iii) Rapid growth phase (2018–2023): Characterized by the implementation of policies, the success of practical cases [46], and the active promotion by social groups, which led to a qualitative increase in the number of articles in 2019 [44], with numbers remaining high in the subsequent years.
This research indicates that Y. Miyazaki is the most prolific author, who has published 27 papers since 2006, primarily studying factors in forest environments that affect psychological health [8,47,48,49]. The author with the highest citation count, T. Kagawa, has received 2465 citations, averaging 136.9 citations per article. Kagawa’s research focuses on the effects of forest bathing on individuals across different age groups [50,51,52,53].
Over time, the number of authors engaging in academic exchanges has decreased, with most scholars having no such interactions and only a small, relatively concentrated group participating in cooperation. The Forestry and Forest Products Research Institute in Japan stands out as the leading institution in publishing research on the effects of forest therapy on mental health, with a total of 34 papers. Additionally, it serves as a central hub for collaborative efforts, maintaining strong ties with numerous institutes across the field. This emphasis on international cooperation fosters the sharing of knowledge and experiences, enhances research standards, and ultimately leads to the production of high-quality outputs.
Apart from China, Japan, and South Korea, most countries leading in the field tend to operate independently, prioritizing individual efforts over international collaboration to attain high-quality results. Notably, South Korea boasts the highest multi-country publication rate, standing at 95%. A total of 42 countries have contributed to research on the effects of forest therapy on mental health, with Japan leading in output, followed by South Korea. While scholars from all five continents are involved, Africa’s participation is limited, with only Egypt being actively engaged. Japan and South Korea emerge as frontrunners in this research domain, with China having the highest publication count. Notably, Japan’s research stands out with the highest average citation rate, underscoring its central role in the field.
Based on published journals, research on the effects of forest therapy on mental health is interdisciplinary, encompassing fields such as forestry, ecology, psychology, environmental psychology, traditional Chinese medicine, management, and psychiatry. Among these, forestry, ecology, and psychology are the most important subjects [54]. The psychotherapeutic benefits of forest therapy stem from biogenic volatile organic compounds (BVOCs) emitted by trees, which accumulate in the atmosphere [55,56,57]. These compounds, known as phytoncides, reduce the levels of cortisol and adrenaline (stress hormones) in the body, thereby alleviating anxiety and fatigue [57,58]. Terpenes and terpenoids are the main BVOCs in forest aerosols [59]. However, not all plants emit useful biovolatile compounds. Natural tree species such as Cunninghamia lanceolata, coniferous trees (e.g., Pinus spp., Abies spp., and Cupressus spp.) [60], Firmiana simplex, colorful-leaved trees (e.g., Acer palmatum and Euonymus japonicus “Aureomarginatus”), and bamboo are good choices [61,62,63]. Some indoor plants also have corresponding effects, such as the peace lily (Spathiphyllum wallisii) and the iron plant (Aspidistra elatior) [64].
The volatile compounds emitted by these plants, including limonene, terpenoids, flavonoids, phenols, aliphatic compounds, phytoncides, and aromatic compounds [65,66,67], are beneficial to the human body. For example, as monoterpene (MT) levels rose from 0 to 20 ppbv, the average brain alpha wave values among participants increased from 9.8 to 15.1 [58,68]. It is worth noting that the effective concentration range of these compounds still needs to be studied.
At the same time, the stimulation of the human body’s five senses through relaxing activities in the forest can reduce fatigue, enhance relaxation, improve mood, and regulate emotions [32]. These factors contribute to an increase in the content of natural-killer cells (NK cells) in the immune system, which help to improve immunity and resist tumor growth [33].
The burst detection analysis of keywords identified the top seven keywords with the highest outbreak strength. “Atmosphere” emerged as the first and longest-lasting keyword, displaying the most intense outbreak. This practice involves deliberate, leisurely walks through wooded areas, engaging all bodily senses and enabling a deeply immersive healing experience in nature, often described as connecting with the forest atmosphere [69,70]. Additionally, we observed a notable surge in citations of keywords like “salivary cortisol”, “urban environment”, and “heart rate variability” during a specific period five years ago. This may be due to the fact that the influencing components of the forest environment, including BVOCs and negative air ions (NAIs), are gradually being validated by scientific research. Both heart rate and cortisol levels are affected by these components. With the intensification of urbanization, the urbanization model incorporating forest elements, such as gardens, parks, and greenways, has become increasingly integrated into people’s lives [35,71,72]. The thematic evolution diagram of the keywords involved in the research on the effects of forest therapy on mental health can be summarized into three types: exploratory development, research intensification, and comprehensive innovation.
Through thematic analysis, we can trace the origin of the spiritual healing effects of forest therapy back to the Attention Restoration Theory [73]. This theory primarily involves people immersing themselves in natural environments and focusing on their own sensations. Gradually, it becomes apparent that this practice is conducive to reducing depression, anxiety, stress, and anger in both clinical and non-clinical samples, particularly for anxiety [74,75,76]. In recent years, psychological constructs like self-compassion and psychological safety have been explored, as nature exposure may activate our soothing system, fostering compassion, safety, and connection, thereby safeguarding mental health [77]. Engaging in forest bathing and connecting with nature can help regulate emotions, leading to a sense of peace and tranquility rather than fear, anxiety, and stress [78].
In addition to BVOCs, NAIs in forest air also provide significant health benefits, including improving metabolism and blood circulation, increasing comfort, aiding in recovery from fatigue, and maintaining overall health [79]. Studies have shown that negative air ions can enhance sleep quality and alleviate insomnia and anxiety by regulating neurotransmitter levels, such as dopamine and serotonin, in the brain [80,81]. Furthermore, negative air ions can improve the body’s resistance to stress and promote the secretion of cortisol, a hormone often associated with stress and fatigue [82]. However, the role of nature in affect regulation is often overlooked [83,84].
Through the accumulation of scientific evidence and the inspiration of theoretical research, we can summarize the mechanism by which forest environments impact human mental health into three main points: (i) Mechanism of Frequency Resonance: The magnetic field of the forest environment adjusts the vibration frequency of particles in the human body, restarts the body’s self-healing ability, alters the human energy field, and causes same-frequency resonance, thereby improving mood and regulating mental health [80]. (ii) Mechanism of Dynamic Brain Stereotyping: This mechanism leverages the natural emotional connection between humans and forests to form a stable dynamic stereotype, making the individual’s healing experience in the forest environment a conditioned reflex physiological mechanism [9]. (iii) Mechanism of Sensory Environmental Stimulation (Five Senses Stimulation Mechanism): This mechanism activates the individual’s vision, hearing, smell, touch, and taste through natural elements in the forest environment, helping people to relieve the fatigue and tension of urban life, thereby achieving relaxation, healing, and health preservation [3,85].

4.2. Limitations and Future Research

Due to constraints on database access and their search capabilities, certain articles might have been omitted. Additionally, considering the inherent limitations of bibliometrics, its conclusions may require further clarification through content analysis [86]. Further constraints may arise due to the limited scope of the primary literature data, which include only English-language studies, potentially overlooking relevant research published in other languages [87]. Despite the promising results observed in all included studies, the risk of bias was assessed as medium to high, and nearly all analyses revealed potential publication bias. This could elucidate why Japanese and Asian participants, belonging to cultures that embrace nature’s healing effects, might experience greater benefits from forest therapy [88]. Additional limitations in forest therapy research include insufficient follow-up assessments and consideration for sample representativeness, which can compromise the validity of clinical research by leaving uncertainty regarding the duration of forest therapy effects [89].
In future studies, assessing the sustained effects of forest therapy on mental health programs is crucial. Nevertheless, most of the studies incorporated in this analysis refrained from assessing these impacts, possibly due to insufficient research funding. Imprecise conclusions may result if the sustainability of forest therapy’s impact on the psychological states of participants is evaluated without adhering to scientific control variable methods. The optimal duration of exposure for forest-based stress and anxiety therapy programs remains unknown. To examine dose–response relationships, researchers should consider variations in duration (e.g., one week, two weeks, and three weeks) and frequency (e.g., once a week vs. twice a week vs. three times a week). Moreover, there is a need for more high-quality studies to better understand the causal relationship between forest therapy programs and mental health issues such as stress relief. Some findings have emerged from studies with inherent design flaws.
To enhance the sustainability and safety of forest therapy research, it is crucial to effectively utilize abundant forest resources. Researchers should explore forest environments, terrain, altitude, climate, and air conditions suitable for various types of forest therapy. For instance, understanding “how to manage forests” could lead to potential developments in forest therapy. Therefore, further research is necessary to explore the relationship between forest characteristics and mental health in order to provide information for forest therapy-oriented management [90]. This involves investigating all variables that impact forest landscapes, including forest types, tree species composition, age structure, canopy density, and the abundance of deadwood [63].

5. Conclusions

Based on a bibliometric analysis of publications from 2006 to 2023, research on the effects of forest therapy on mental health has entered a phase of rapid development since 2019. The top four authors in terms of publication volume, including Yoshifumi Miyazaki and Takashi Kagawa, are from Japan, while the fifth-ranked author, Chorong Song, is from South Korea. In recent years, new researchers in this field have not established close collaborations with these leading authors, primarily engaging in small-scale, region-based collaborations.
Japan and South Korea are at the forefront of initiating research and establishing standards for research outcomes. This leadership is attributed to the tradition in Asia that emphasizes the relationship between humans and nature in medicine, as well as the region’s abundant forest resources, similar to the case of Bad Wörishofen in Germany. In recent years, driven by market demand, national policies, and the active promotion by international organizations such as the INFOM, this field has experienced rapid growth in countries such as China, the United States, the United Kingdom, and Italy.
Research indicates that forest therapy activities can reduce cortisol levels, heart rate, and blood pressure, while enhancing parasympathetic nervous activity and reducing sympathetic nervous activity. These physiological changes help alleviate stress and anxiety. Additionally, factors such as negative ions, BVOCs, and phytoncides in forest environments can boost the immune system, positively impacting mental health by effectively reducing anxiety and depression levels and promoting pro-environmental behavior. Moreover, forest therapy has been shown to stimulate local tourism, physical activities, and economic development while also reducing healthcare costs. However, it faces challenges in balancing forest resource development, management, and ecological protection.

Author Contributions

Conceptualization, Q.Q.; methodology, Q.Q.; software, R.W. (Ruoyu Wan) and R.W. (Ruohong Wan); validation, Q.Q.; formal analysis, R.W. (Ruoyu Wan); investigation, R.W. (Ruoyu Wan) and R.W. (Ruohong Wan); resources, R.W. (Ruoyu Wan); data curation, R.W. (Ruohong Wan); writing—original draft preparation, R.W. (Ruoyu Wan); writing—review and editing, R.W. (Ruoyu Wan); visualization, R.W. (Ruoyu Wan); supervision, R.W. (Ruohong Wan); project administration, R.W. (Ruohong Wan); funding acquisition, R.W. (Ruoyu Wan). All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by Huazhong University of Science and Technology Student Innovation and Entrepreneurship Projects, grant number S202310487329.

Data Availability Statement

All datasets presented in this study can be found within the article.

Conflicts of Interest

The authors declare no conflicts of interest.

Appendix A

Forests 15 01013 g0a1
Figure A1. The country cooperation network. The nodes represent the countries. Critical nodes are highlighted with purple rings. The line between countries indicates a collaborative relationship. The thicker the line, the more frequently they collaborate. (For interpretation of the references’ colors in this figure, the reader is referred to the legend in the upper left corner.) Analysis performed by using CiteSpace.
Figure A1. The country cooperation network. The nodes represent the countries. Critical nodes are highlighted with purple rings. The line between countries indicates a collaborative relationship. The thicker the line, the more frequently they collaborate. (For interpretation of the references’ colors in this figure, the reader is referred to the legend in the upper left corner.) Analysis performed by using CiteSpace.
Forests 15 01013 g0a1
Forests 15 01013 g0a2
Figure A2. The thematic evolution diagram. The diagram illustrates the impact of forest therapy on publications related to mental health from 2006 to 2023: analysis performed by using Bibliometrix.
Figure A2. The thematic evolution diagram. The diagram illustrates the impact of forest therapy on publications related to mental health from 2006 to 2023: analysis performed by using Bibliometrix.
Forests 15 01013 g0a2

References

  1. Hansen, M.M.; Jones, R.; Tocchini, K. Shinrin-Yoku (Forest Bathing) and Nature Therapy: A State-of-the-Art Review. Int. J. Environ. Res. Public Health 2017, 14, 851. [Google Scholar] [CrossRef] [PubMed]
  2. Yamaguchi, M.; Deguchi, M.; Miyazaki, Y. The effects of exercise in forest and urban environments on sympathetic nervous activity of normal young adults. J. Int. Med. Res. 2006, 34, 152–159. [Google Scholar] [CrossRef] [PubMed]
  3. Hansen, M.M.; Jones, R. The Interrelationship of Shinrin-Yoku and Spirituality: A Scoping Review. J. Altern. Complement. Med. 2020, 26, 1093–1104. [Google Scholar] [CrossRef] [PubMed]
  4. Jo, H.; Song, C.R.; Ikei, H.; Enomoto, S.; Kobayashi, H.; Miyazaki, Y. Physiological and Psychological Effects of Forest and Urban Sounds Using High-Resolution Sound Sources. Int. J. Environ. Res. Public Health 2019, 16, 2649. [Google Scholar] [CrossRef] [PubMed]
  5. Joung, D.; Kim, G.; Choi, Y.; Lim, H.; Park, S.; Woo, J.M.; Park, B.J. The Prefrontal Cortex Activity and Psychological Effects of Viewing Forest Landscapes in Autumn Season. Int. J. Environ. Res. Public Health 2015, 12, 7235–7243. [Google Scholar] [CrossRef] [PubMed]
  6. Kim, C.; Kim, J.; Song, I.J.; Yi, Y.J.; Park, B.J.; Song, C.R. The Effects of Forest Walking on Physical and Mental Health Based on Exercise Prescription. Forests 2023, 14, 2332. [Google Scholar] [CrossRef]
  7. Lee, J.; Tsunetsugu, Y.; Takayama, N.; Park, B.J.; Li, Q.; Song, C.; Komatsu, M.; Ikei, H.; Tyrväinen, L.; Kagawa, T.; et al. Influence of Forest Therapy on Cardiovascular Relaxation in Young Adults. Evid.-Based Complement. Altern. Med. 2014, 2014, 834360. [Google Scholar] [CrossRef] [PubMed]
  8. Song, C.R.; Ikei, H.; Miyazaki, Y. Effects of forest-derived visual, auditory, and combined stimuli. Urban For. Urban Green. 2021, 64, 127253. [Google Scholar] [CrossRef]
  9. Kotera, Y.; Richardson, M.; Sheffield, D. Effects of Shinrin-Yoku (Forest Bathing) and Nature Therapy on Mental Health: A Systematic Review and Meta-Analysis. Int. J. Ment. Health Addict. 2020, 20, 337–361. [Google Scholar] [CrossRef]
  10. Wei, H.X.; Hauer, R.J.; Guo, S.L. Daytime dynamic of spontaneous expressions of pedestrians in an urban forest park. Urban For. Urban Green. 2021, 65, 127326. [Google Scholar] [CrossRef]
  11. Janeczko, E.; Górski, J.; Woznicka, M.; Czyzyk, K.; Kedziora, W.; Korcz, N. Physical Activity in Forest and Psychological Health Benefits: A Field Experiment with Young Polish Adults. Forests 2023, 14, 1904. [Google Scholar] [CrossRef]
  12. Park, S.; Kim, E.; Kim, G.; Kim, S.; Choi, Y.; Paek, D. What Activities in Forests Are Beneficial for Human Health? A Systematic Review. Int. J. Environ. Res. Public Health 2022, 19, 2692. [Google Scholar] [CrossRef] [PubMed]
  13. Kobayashi, H.; Ikei, H.; Song, C.; Kagawa, T.; Miyazaki, Y. Comparing the impact of forest walking and forest viewing on psychological states. Urban For. Urban Green. 2021, 57, 126920. [Google Scholar] [CrossRef]
  14. Meyer, K.; Bürger-Arndt, R. How forests foster human health—Present state of research-based knowledge (in the field of Forests and Human Health). Int. For. Rev. 2014, 16, 421–446. [Google Scholar] [CrossRef]
  15. Balanza-Martínez, V.; Cervera-Martínez, J. Lifestyle Prescription for Depression with a Focus on Nature Exposure and Screen Time: A Narrative Review. Int. J. Environ. Res. Public Health 2022, 19, 5094. [Google Scholar] [CrossRef]
  16. Preston, S.D.; Tansfield, R.B.S.; Buchanan, T.W.; Bechara, A. Effects of anticipatory stress on decision making in a gambling task. Behav. Neurosci. 2007, 121, 257–263. [Google Scholar] [CrossRef]
  17. Adewuyi, F.A.; Knobel, P.; Gogna, P.; Dadvand, P. Health effects of green prescription: A systematic review of randomized controlled trials. Environ. Res. 2023, 236, 116844. [Google Scholar] [CrossRef] [PubMed]
  18. Antonelli, M.; Donelli, D.; Carlone, L.; Maggini, V.; Firenzuoli, F.; Bedeschi, E. Effects of forest bathing (shinrin-yoku) on individual well-being: An umbrella review. Int. J. Environ. Health Res. 2022, 32, 1842–1867. [Google Scholar] [CrossRef]
  19. Donthu, N.; Kumar, S.; Mukherjee, D.; Pandey, N.; Lim, W.M. How to conduct a bibliometric analysis: An overview and guidelines. J. Bus. Res. 2021, 133, 285–296. [Google Scholar] [CrossRef]
  20. Zeleznik, D.; Vosner, H.B.; Kokol, P. A bibliometric analysis of the Journal of Advanced Nursing, 1976–2015. J. Adv. Nurs. 2017, 73, 2407–2419. [Google Scholar] [CrossRef]
  21. Mukherjee, D.; Lim, W.M.; Kumar, S.; Donthu, N. Guidelines for advancing theory and practice through bibliometric research. J. Bus. Res. 2022, 148, 101–115. [Google Scholar] [CrossRef]
  22. Klarin, A. How to conduct a bibliometric content analysis: Guidelines and contributions of content co-occurrence or co-word literature reviews. Int. J. Consum. Stud. 2024, 48, e13031. [Google Scholar] [CrossRef]
  23. Baker, H.K.; Kumar, S.; Pandey, N. Forty years of the Journal of Futures Markets: A bibliometric overview. J. Futures Mark. 2021, 41, 1027–1054. [Google Scholar] [CrossRef]
  24. Morato, J.L.; Llorens, J.; Sánchez-Cuadrado, S.; Genova, G. Guidelines for the development of an automatic system to measure bibliometric indicators. In Proceedings of the 7th World Multiconference on Systemics, Cybernetics and Informatics, Orlando, FL, USA, 27–30 July 2003; pp. 374–379. [Google Scholar]
  25. Montazeri, A.; Mohammadi, S.; Hesari, P.M.; Ghaemi, M.; Riazi, H.; Sheikhi-Mobarakeh, Z. Preliminary guideline for reporting bibliometric reviews of the biomedical literature (BIBLIO): A minimum requirements. Syst. Rev. 2023, 12, 239. [Google Scholar] [CrossRef] [PubMed]
  26. Cheng, K.; Li, Z.; Sun, Z.; Guo, Q.; Li, W.; Lu, Y.; Qi, S.; Shen, Z.; Xie, R.; Wang, Y.; et al. The rapid growth of bibliometric studies: A call for international guidelines (Correspondence). Int. J. Surg. 2024, 110, 2446–2448. [Google Scholar] [CrossRef]
  27. van Eck, N.J.; Waltman, L. Software survey: VOSviewer, a computer program for bibliometric mapping. Scientometrics 2010, 84, 523–538. [Google Scholar] [CrossRef]
  28. Chen, C. Science Mapping: A Systematic Review of the Literature. J. Data Inf. Sci. 2017, 2, 1–40. [Google Scholar] [CrossRef]
  29. Zhang, X.; Antwi-Afari, M.F.; Zhang, Y.; Xing, X. The Impact of Artificial Intelligence on Organizational Justice and Project Performance: A Systematic Literature and Science Mapping Review. Buildings 2024, 14, 259. [Google Scholar] [CrossRef]
  30. Aria, M.; Cuccurullo, C. bibliometrix: An R-tool for comprehensive science mapping analysis. J. Informetr. 2017, 11, 959–975. [Google Scholar] [CrossRef]
  31. Wang, X.; Xu, Z.; Qin, Y. Structure, trend and prospect of operational research: A scientific analysis for publications from 1952 to 2020 included in Web of Science database. Fuzzy Optim. Decis. Mak. 2022, 21, 649–672. [Google Scholar] [CrossRef]
  32. Brod, S.; Rattazzi, L.; Piras, G.; D’Acquisto, F. ‘As above, so below’ examining the interplay between emotion and the immune system. Immunology 2014, 143, 311–318. [Google Scholar] [CrossRef] [PubMed]
  33. Ayling, K.; Sunger, K.; Vedhara, K. Effects of Brief Mood-Improving Interventions on Immunity: A Systematic Review and Meta-Analysis. Psychosom. Med. 2020, 82, 10–28. [Google Scholar] [CrossRef] [PubMed]
  34. Song, J.B.; Zhang, H.L.; Dong, W.L. A review of emerging trends in global PPP research: Analysis and visualization. Scientometrics 2016, 107, 1111–1147. [Google Scholar] [CrossRef]
  35. Kim, J.G.; Jeon, J.; Shin, W.S. The Influence of Forest Activities in a University Campus Forest on Student’s Psychological Effects. Int. J. Environ. Res. Public Health 2021, 18, 2457. [Google Scholar] [CrossRef] [PubMed]
  36. Baek, J.E.; Jung, J.H.; Shin, H.J.; Kim, S.H.; Sung, S.Y.; Park, S.J.; Hahm, S.C.; Cho, H.Y.; Lee, M.G. Effects of Forest Healing Anti-Aging Program on Psychological, Physiological, and Physical Health of Older People with Mild Cognitive Impairment. Int. J. Environ. Res. Public Health 2022, 19, 4863. [Google Scholar] [CrossRef]
  37. Duan, W.; Wang, C.; Pei, N.; Zhang, C.; Gu, L.; Jiang, S.; Hao, Z.; Xu, X. Urban forests increase spontaneous activity and improve emotional state of white mice. Urban For. Urban Green. 2019, 46, 126449. [Google Scholar] [CrossRef]
  38. Li, H.S.; Zhang, X.; Bi, S.L.; Cao, Y.; Zhang, G.D. Psychological benefits of green exercise in wild or urban greenspaces: A meta-analysis of controlled trials. Urban For. Urban Green. 2022, 68, 127458. [Google Scholar] [CrossRef]
  39. Zhu, S.; He, S.; Hu, F.; Guo, Y.; Su, Y.; Cui, G.; Li, J.; Qiu, Q.; He, Q. Exurban and suburban forests have superior healthcare benefits beyond downtown forests. Front. Ecol. Evol. 2023, 11, 1105213. [Google Scholar] [CrossRef]
  40. Liu, Q.H.; Wang, X.P.; Liu, J.L.; An, C.Y.; Liu, Y.Q.; Fan, X.L.; Hu, Y.S. Physiological and Psychological Effects of Nature Experiences in Different Forests on Young People. Forests 2021, 12, 1391. [Google Scholar] [CrossRef]
  41. Jowsey, T.; Deng, C.; Weller, J. General-purpose thematic analysis: A useful qualitative method for anaesthesia research. BJA Educ. 2021, 21, 472–478. [Google Scholar] [CrossRef]
  42. Piva, G.; Caruso, L.; Gómez, A.C.; Calzolari, M.; Visintin, E.P.; Davoli, P.; Manfredini, F.; Storari, A.; Spinozzi, P.; Lamberti, N. Effects of forest walking on physical and mental health in elderly populations: A systematic review. Rev. Environ. Health 2024, 39, 121–136. [Google Scholar] [CrossRef] [PubMed]
  43. Dodev, Y.; Zhiyanski, M.; Glushkova, M.; Shin, W.S. Forest welfare services—The missing link between forest policy and management in the EU. For. Policy Econ. 2020, 118, 102249. [Google Scholar] [CrossRef]
  44. Hou, Y.; Cong, L. Forest-based Wellness in Japan: Policy Evolution and Its Enlightenment. World For. Res. 2022, 35, 82–87. [Google Scholar]
  45. Zhang, Z.; Wang, P.; Gao, Y.; Ye, B. Current Development Status of Forest Therapy in China. Healthcare 2020, 8, 61. [Google Scholar] [CrossRef] [PubMed]
  46. Zhang, S.; Teng, J.; Zeng, Y.; Song, H.; Gu, Z. The effects of forest therapy on public mental health and circular economy: A policy support model in Japan. Front. Public Health 2022, 10, 1042589. [Google Scholar] [CrossRef] [PubMed]
  47. Li, H.; Xu, M.R.; Li, J.Z.; Li, Z.Y.; Wang, Z.Y.; Zhuang, W.J.; Li, C.Y. Spatial Distribution Characteristics of Japan’s Forest Therapy Bases and Their Influencing Factors. Sustainability 2022, 14, 15156. [Google Scholar] [CrossRef]
  48. Ochiai, H.; Song, C.R.; Jo, H.; Oishi, M.; Imai, M.; Miyazaki, Y. Relaxing Effect Induced by Forest Sound in Patients with Gambling Disorder. Sustainability 2020, 12, 5969. [Google Scholar] [CrossRef]
  49. Song, C.R.; Ikei, H.; Miyazaki, Y. Physiological effects of forest-related visual, olfactory, and combined stimuli on humans: An additive combined effect. Urban For. Urban Green. 2019, 44, 7. [Google Scholar] [CrossRef]
  50. Song, C.R.; Ikei, H.; Kagawa, T.; Miyazaki, Y. Physiological and Psychological Effects of Viewing Forests on Young Women. Forests 2019, 10, 635. [Google Scholar] [CrossRef]
  51. Song, C.R.; Ikei, H.; Kobayashi, M.; Miura, T.; Li, Q.; Kagawa, T.; Kumeda, S.; Imai, M.; Miyazaki, Y. Effects of viewing forest landscape on middle-aged hypertensive men. Urban For. Urban Green. 2017, 21, 247–252. [Google Scholar] [CrossRef]
  52. Li, Q.; Kobayashi, M.; Kumeda, S.; Ochiai, T.; Miura, T.; Kagawa, T.; Imai, M.; Wang, Z.; Otsuka, T.; Kawada, T. Effects of Forest Bathing on Cardiovascular and Metabolic Parameters in Middle-Aged Males. Evid.-Based Complement Altern. Med. 2016, 2016, 2587381. [Google Scholar] [CrossRef]
  53. Ochiai, H.; Ikei, H.; Song, C.; Kobayashi, M.; Miura, T.; Kagawa, T.; Li, Q.; Kumeda, S.; Imai, M.; Miyazaki, Y. Physiological and Psychological Effects of a Forest Therapy Program on Middle-Aged Females. Int. J. Environ. Res. Public Health 2015, 12, 15222–15232. [Google Scholar] [CrossRef] [PubMed]
  54. Zhang, Y.W.; Feng, L.; Duan, W.J. The Impact of Forest Therapy Programs on Stress Reduction: A Systematic Review. Forests 2023, 14, 1851. [Google Scholar] [CrossRef]
  55. Meneguzzo, F.; Albanese, L.; Bartolini, G.; Zabini, F. Temporal and Spatial Variability of Volatile Organic Compounds in the Forest Atmosphere. Int. J. Environ. Res. Public Health 2019, 16, 4915. [Google Scholar] [CrossRef]
  56. Roviello, V.; Gilhen-Baker, M.; Vicidomini, C.; Roviello, G.N. Forest-bathing and physical activity as weapons against COVID-19: A review. Environ. Chem. Lett. 2022, 20, 131–140. [Google Scholar] [CrossRef] [PubMed]
  57. Le Gear, K.; Carlin, C.; Flaherty, G.T. Deep roots: Realising the public health benefits of exposure to forest environments. Adv. Integr. Med. 2023, 10, 86–88. [Google Scholar] [CrossRef]
  58. Donelli, D.; Meneguzzo, F.; Antonelli, M.; Ardissino, D.; Niccoli, G.; Gronchi, G.; Baraldi, R.; Neri, L.; Zabini, F. Effects of Plant-Emitted Monoterpenes on Anxiety Symptoms: A Propensity-Matched Observational Cohort Study. Int. J. Environ. Res. Public Health 2023, 20, 2773. [Google Scholar] [CrossRef]
  59. Kim, T.; Song, B.; Cho, K.S.; Lee, I.-S. Therapeutic Potential of Volatile Terpenes and Terpenoids from Forests for Inflammatory Diseases. Int. J. Mol. Sci. 2020, 21, 2187. [Google Scholar] [CrossRef] [PubMed]
  60. Li, H.S.; Zhang, G.D. How can plant-enriched natural environments benefit human health: A narrative review of relevant theories. Int. J. Environ. Health Res. 2023, 34, 1241–1254. [Google Scholar] [CrossRef]
  61. Zhu, S.X.; Hu, F.F.; He, S.Y.; Qiu, Q.; Su, Y.; He, Q.; Li, J.Y. Comprehensive Evaluation of Healthcare Benefits of Different Forest Types: A Case Study in Shimen National Forest Park, China. Forests 2021, 12, 207. [Google Scholar] [CrossRef]
  62. Takayama, N.; Saito, H.; Fujiwara, A.; Horiuchi, M. The effect of slight thinning of managed coniferous forest on landscape appreciation and psychological restoration. Prog. Earth Planet. Sci. 2017, 4, 17. [Google Scholar] [CrossRef]
  63. Liu, Q.; Wang, X.; Liu, J.; Zhang, G.; An, C.; Liu, Y.; Fan, X.; Hu, Y.; Zhang, H. The Relationship between the Restorative Perception of the Environment and the Physiological and Psychological Effects of Different Types of Forests on University Students. Int. J. Environ. Res. Public Health 2021, 18, 12224. [Google Scholar] [CrossRef] [PubMed]
  64. Roviello, V.; Scognamiglio, P.L.; Caruso, U.; Vicidomini, C.; Roviello, G.N. Evaluating In Silico the Potential Health and Environmental Benefits of Houseplant Volatile Organic Compounds for an Emerging ‘Indoor Forest Bathing’ Approach. Int. J. Environ. Res. Public Health 2022, 19, 273. [Google Scholar] [CrossRef]
  65. Walker, H.; Jena, A.; McEwan, K.; Evans, G.; Campbell, S. Natural Volatile Organic Compounds (NVOCs) Are Greater and More Diverse in UK Forests Compared with a Public Garden. Forests 2023, 14, 92. [Google Scholar] [CrossRef]
  66. Wu, J.; Wang, Q.; Xu, C.; Lun, X.; Wang, L.; Gao, Y.; Huang, L.; Zhang, Q.; Li, L.; Liu, B.; et al. Biogenic volatile organic compounds in forest therapy base: A source of air pollutants or a healthcare function? Sci. Total Environ. 2024, 931, 172944. [Google Scholar] [CrossRef] [PubMed]
  67. Sundermann, M.; Chielli, D.; Spell, S. Nature as Medicine: The 7th (Unofficial) Pillar of Lifestyle Medicine. Am. J. Lifestyle Med. 2023, 17, 717–729. [Google Scholar] [CrossRef] [PubMed]
  68. Kim, J.-C.; Dinh, T.-V.; Oh, H.-K.; Son, Y.-S.; Ahn, J.-W.; Song, K.-Y.; Choi, I.-Y.; Park, C.-R.; Szulejko, J.E.; Kim, K.-H. The Potential Benefits of Therapeutic Treatment Using Gaseous Terpenes at Ambient Low Levels. Appl. Sci. 2019, 9, 4507. [Google Scholar] [CrossRef]
  69. Bielinis, E.; Omelan, A.; Boiko, S.; Bielinis, L. The Restorative Effect of Staying in a Broad-Leaved Forest on Healthy Young Adults in Winter and Spring. Baltic For. 2018, 24, 218–227. [Google Scholar]
  70. Lim, P.Y.; Dillon, D.; Chew, P.K.H. A Guide to Nature Immersion: Psychological and Physiological Benefits. Int. J. Environ. Res. Public Health 2020, 17, 5989. [Google Scholar] [CrossRef]
  71. Elsadek, M.; Liu, B.Y.; Lian, Z.F.; Xie, J.F. The influence of urban roadside trees and their physical environment on stress relief measures: A field experiment in Shanghai. Urban For. Urban Green. 2019, 42, 51–60. [Google Scholar] [CrossRef]
  72. Hong, J.; Park, S.; An, M. Are Forest healing programs useful in promoting children’s emotional welfare? The Interpersonal relationships of children in foster care. Urban For. Urban Green. 2021, 59, 127034. [Google Scholar] [CrossRef]
  73. Kim, W.; Lim, S.-K.; Chung, E.-J.; Woo, J.-M. The Effect of Cognitive Behavior Therapy-Based Psychotherapy Applied in a Forest Environment an Physiological Changes and Remission of Major Depressive Disorder. Psychiatry Investig. 2009, 6, 245–254. [Google Scholar] [CrossRef]
  74. Vujcic, M.; Tomicevic-Dubljevic, J.; Grbic, M.; Lecic-Tosevski, D.; Vukovic, O.; Toskovic, O. Nature based solution for improving mental health and well-being in urban areas. Environ. Res. 2017, 158, 385–392. [Google Scholar] [CrossRef]
  75. Morita, E.; Fukuda, S.; Nagano, J.; Hamajima, N.; Yamamoto, H.; Iwai, Y.; Nakashima, T.; Ohira, H.; Shirakawa, T. Psychological effects of forest environments on healthy adults: Shinrin-yoku (forest-air bathing, walking) as a possible method of stress reduction. Public Health 2007, 121, 54–63. [Google Scholar] [CrossRef] [PubMed]
  76. Ulrich, R.S.; Simons, R.F.; Losito, B.D.; Fiorito, E.; Miles, M.A.; Zelson, M. Stress recovery during exposure to natural and urban environments. J. Environ. Psychol. 1991, 11, 201–230. [Google Scholar] [CrossRef]
  77. Nisbet, E.K.; Zelenski, J.M.; Murphy, S.A. The nature relatedness scale: Linking individuals’ connection with nature to environmental concern and behavior. Sage J. 2008, 41, 715–740. [Google Scholar] [CrossRef]
  78. Richardson, M.; McEwan, K.; Maratos, F.; Sheffield, D. Joy and Calm: How an Evolutionary Functional Model of Affect Regulation Informs Positive Emotions in Nature. Evol. Psychol. Sci. 2016, 2, 308–320. [Google Scholar] [CrossRef]
  79. Liu, S.; Li, C.; Chu, M.; Zhang, W.; Wang, W.; Wang, Y.; Guo, X.; Deng, F. Associations of forest negative air ions exposure with cardiac autonomic nervous function and the related metabolic linkages: A repeated-measure panel study. Sci. Total Environ. 2022, 850, 158019. [Google Scholar] [CrossRef]
  80. Wang, R.; Chen, Q.; Wang, D. Effects of Altitude, Plant Communities, and Canopies on the Thermal Comfort, Negative Air Ions, and Airborne Particles of Mountain Forests in Summer. Sustainability 2022, 14, 3882. [Google Scholar] [CrossRef]
  81. Li, A.; Li, Q.; Yang, Y.; Hu, Y.; Xiao, S.; Li, Z.; Zhou, B. Stand structure and environment jointly determine negative air ion concentrations in forests: Evidence from concurrent on-site monitoring in four typical subtropical forests during the growing season. Environ. Exp. Bot. 2024, 220, 105684. [Google Scholar] [CrossRef]
  82. Antonelli, M.; Barbieri, G.; Donelli, D. Effects of forest bathing (shinrin-yoku) on levels of cortisol as a stress biomarker: A systematic review and meta-analysis. Int. J. Biometeorol. 2019, 63, 1117–1134. [Google Scholar] [CrossRef] [PubMed]
  83. Korpela, K.; Nummi, T.; Lipiäinen, L.; De Bloom, J.; Sianoja, M.; Pasanen, T.; Kinnunen, U. Nature exposure predicts well-being trajectory groups among employees across two years. J. Environ. Psychol. 2017, 52, 81–91. [Google Scholar] [CrossRef]
  84. Walsh, L.M.; Benjamin Wolk, C.; Becker-Haimes, E.M.; Jensen-Doss, A.; Beidas, R.S. The Relationship Between Anger and Anxiety Symptoms in Youth with Anxiety Disorders. J. Child Adolesc. Couns. 2018, 4, 117–133. [Google Scholar] [CrossRef] [PubMed]
  85. Kanelli, A.A.; Dimitrakopoulos, P.G.; Fyllas, N.M.; Chrousos, G.P.; Kalantzi, O.I. Engaging the Senses: The Association of Urban Green Space with General Health and Well-Being in Urban Residents. Sustainability 2021, 13, 7322. [Google Scholar] [CrossRef]
  86. Huang, W.; Lin, G. The relationship between urban green space and social health of individuals: A scoping review. Urban For. Urban Green. 2023, 85, 127969. [Google Scholar] [CrossRef]
  87. Rasmussen, L.N.; Montgomery, P. The prevalence of and factors associated with inclusion of non-English language studies in Campbell systematic reviews: A survey and meta-epidemiological study. Syst. Rev. 2018, 7, 129. [Google Scholar] [CrossRef] [PubMed]
  88. Gierlach, E.; Belsher, B.E.; Beutler, L.E. Cross-cultural differences in risk perceptions of disasters. Risk Anal. 2010, 30, 1539–1549. [Google Scholar] [CrossRef]
  89. Dettori, J.R.; Tacoma, W.A. Loss to follow-up. Evid. Based Spine Care 2011, 4, 5–58. [Google Scholar] [CrossRef]
  90. Thomas, T.; Baker, J.; Massey, D.; D’Appio, D.; Aggar, C. Stepped-Wedge Cluster Randomised Trial of Social Prescribing of Forest Therapy for Quality of Life and Biopsychosocial Wellbeing in Community-Living Australian Adults with Mental Illness: Protocol. Int. J. Environ. Res. Public Health 2020, 17, 9076. [Google Scholar] [CrossRef]
Forests 15 01013 g001
Figure 1. Research framework.
Figure 1. Research framework.
Forests 15 01013 g001
Forests 15 01013 g002
Figure 2. Overall trend of publications and average citations. Annual trend of publications and average citations per article on research on the psychological impact of forest therapy indexed in the Web of Science Core Collection (WoSCC) database during 2006–2023. Analysis performed by using Bibliometrix.
Figure 2. Overall trend of publications and average citations. Annual trend of publications and average citations per article on research on the psychological impact of forest therapy indexed in the Web of Science Core Collection (WoSCC) database during 2006–2023. Analysis performed by using Bibliometrix.
Forests 15 01013 g002
Forests 15 01013 g003
Figure 3. The collaboration network of authors. Each node in the map represents an author. The size of a node reflects the articles that authors have published. According to the legend in the upper right corner, the various colors in the node represent different times when the article has been published. The line indicates the period of collaboration of authors. Analysis performed by using CiteSpace.
Figure 3. The collaboration network of authors. Each node in the map represents an author. The size of a node reflects the articles that authors have published. According to the legend in the upper right corner, the various colors in the node represent different times when the article has been published. The line indicates the period of collaboration of authors. Analysis performed by using CiteSpace.
Forests 15 01013 g003
Forests 15 01013 g004
Figure 4. Affiliation relationships between authors and countries. Tree-field plot of affiliations (items 10), authors (items 12), and countries (items 8), produced by using Bibliometrix.
Figure 4. Affiliation relationships between authors and countries. Tree-field plot of affiliations (items 10), authors (items 12), and countries (items 8), produced by using Bibliometrix.
Forests 15 01013 g004
Forests 15 01013 g005
Figure 5. Country and region collaboration map. Analysis performed by using Bibliometrix.
Figure 5. Country and region collaboration map. Analysis performed by using Bibliometrix.
Forests 15 01013 g005
Forests 15 01013 g006
Figure 6. Corresponding authors’ countries. MCP: multiple-country publications; SCP: single-country publications. Analysis performed by using Bibliometrix.
Figure 6. Corresponding authors’ countries. MCP: multiple-country publications; SCP: single-country publications. Analysis performed by using Bibliometrix.
Forests 15 01013 g006
Forests 15 01013 g007
Figure 7. Core sources according to Bradford’s Law. By using Bradford’s Law principles, Bibliometrix can help researchers determine the most active and influential journals in their dataset, providing valuable insights into the distribution of articles across journals in a particular research domain.
Figure 7. Core sources according to Bradford’s Law. By using Bradford’s Law principles, Bibliometrix can help researchers determine the most active and influential journals in their dataset, providing valuable insights into the distribution of articles across journals in a particular research domain.
Forests 15 01013 g007
Forests 15 01013 g008
Figure 8. Publications co-citation network. Select the “co-citation” file type, and set the unit to “cited sources”. By setting a threshold of 45 co-citation for a source, out of the initial 3722 sources, only 42 keywords met this criterion; analysis performed by using Vosviewer.
Figure 8. Publications co-citation network. Select the “co-citation” file type, and set the unit to “cited sources”. By setting a threshold of 45 co-citation for a source, out of the initial 3722 sources, only 42 keywords met this criterion; analysis performed by using Vosviewer.
Forests 15 01013 g008
Forests 15 01013 g009
Figure 9. Keywords co-occurrence network. Select the “co-occurrence” file type, and set the unit to “all keywords”. By setting a threshold of 15 occurrences for a keyword, out of the initial 1079 keywords, only 38 keywords met this criterion; analysis performed by using VOSviewer.
Figure 9. Keywords co-occurrence network. Select the “co-occurrence” file type, and set the unit to “all keywords”. By setting a threshold of 15 occurrences for a keyword, out of the initial 1079 keywords, only 38 keywords met this criterion; analysis performed by using VOSviewer.
Forests 15 01013 g009
Forests 15 01013 g010
Figure 10. Keyword cluster map. The analysis considers all the keywords and divides them into several clusters. Each cluster has its own color and label. The order of label represents the size of the cluster. The smaller the label number, the more members the cluster contains. The figure neglects the small cluster by pruning the network for a higher-quality illustration. The legend in the left corner references different years of publication. Analysis performed by using CiteSpace.
Figure 10. Keyword cluster map. The analysis considers all the keywords and divides them into several clusters. Each cluster has its own color and label. The order of label represents the size of the cluster. The smaller the label number, the more members the cluster contains. The figure neglects the small cluster by pruning the network for a higher-quality illustration. The legend in the left corner references different years of publication. Analysis performed by using CiteSpace.
Forests 15 01013 g010
Forests 15 01013 g011aForests 15 01013 g011b
Figure 11. Thematic evolution chart. The chart illustrates the influence of forest therapy on publications related to mental health from 2006 to 2023: (a) 2006–2012; (b) 2013–2018; (c) 2019–2023. Analysis performed by using Bibliometrix.
Figure 11. Thematic evolution chart. The chart illustrates the influence of forest therapy on publications related to mental health from 2006 to 2023: (a) 2006–2012; (b) 2013–2018; (c) 2019–2023. Analysis performed by using Bibliometrix.
Forests 15 01013 g011aForests 15 01013 g011b
Forests 15 01013 g012
Figure 12. The top seven keywords with the strongest citation bursts; analysis performed by using CiteSpace.
Figure 12. The top seven keywords with the strongest citation bursts; analysis performed by using CiteSpace.
Forests 15 01013 g012
Table 1. The top 10 most productive authors for related publications on the impact of forest therapy on mental health.
Table 1. The top 10 most productive authors for related publications on the impact of forest therapy on mental health.
RatingAuthorNPTCACh-IndexLCPY-Start
1Y. Miyazaki27231585.74207492006
2T. Kagawa182465136.94167072009
3H. Ikei17114967.59144202014
4N. Takayama1598065.33133232011
5C.R. Song1379361.00112902014
6E. Bielinis1043043.00101322018
7B.J. Park141408100.57104242009
8Q. Li1288573.7593862014
9J. Lee1299282.6782882009
10M. Imai749771.0062572015
Note: Data comes from WoSCC. NP: number of publications; TC: total citations; AC: average citations per article; h-index: Hirsch index, an author-level metric; LC: the author who has been cited the most within a particular region or field; PY-start: year of the first publication.
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Wan, R.; Wan, R.; Qiu, Q. Progress and Prospects of Research on the Impact of Forest Therapy on Mental Health: A Bibliometric Analysis. Forests 2024, 15, 1013. https://doi.org/10.3390/f15061013

AMA Style

Wan R, Wan R, Qiu Q. Progress and Prospects of Research on the Impact of Forest Therapy on Mental Health: A Bibliometric Analysis. Forests. 2024; 15(6):1013. https://doi.org/10.3390/f15061013

Chicago/Turabian Style

Wan, Ruoyu, Ruohong Wan, and Quan Qiu. 2024. "Progress and Prospects of Research on the Impact of Forest Therapy on Mental Health: A Bibliometric Analysis" Forests 15, no. 6: 1013. https://doi.org/10.3390/f15061013

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop