A Scoping Review of Research Trends in Forest Therapy Programs by Subject Types: Focused on KCD-8
Article information
Abstract
Background and objective
This study reviewed forest therapy program studies by applying the scoping review methodology to provide recommendations for future research and basic data for the development of forest therapy programs.
Methods
Data collection was conducted from April 1 to 5, 2022 using South Korean literature databases (RISS, KISS, Science ON, DBpia) and international literature databases (SCOPUS, PubMed, MEDLINE, EMBASE). Focusing on papers published by March 31, 2022, while considering the publication year, we finally selected 118 papers (99 from South Korea and 19 from other countries).
Results
Starting with the first study in 1996, research in South Korea was conducted in earnest since 2006. The study subjects primarily comprised those who were vulnerable to stress, such as office and labor workers, children at community child care centers, and families of patients, followed by mental health and physical patients. In terms of program characteristics, the site types primarily included general forests and forest welfare facilities, and in terms of seasons, summer accounted for the highest proportion, followed by spring and fall, which showed similar proportions. The programs primarily included one-day multiple-session and lodging types. Upon examining the structure of the programs, we observed that the majority of lodging type programs were 3 days and 2 nights programs and 2 days and 1night programs. In contrast, one-day multiple-session programs were primarily conducted in a once-a-week cycle, with 6 to 10 sessions.
Conclusion
Through the results of this study, we examined the current status and scope of forest therapy program research. The findings are expected to be used as a basis for expanding forest therapy program research to collaborate with stakeholders in the health and medical fields in the future.
Introduction
Urbanization has been progressing rapidly, with the global population having approximately doubled in the last 40 years (OECD/European Commission, 2020), which contributes to environmental and noise pollution in cities. These factors can have psychological and physical impacts on humans, leading to severe stress and potentially threatening to their health (Shin, 2009). Previous studies have reported positive effects of visiting natural environments, such as forests, on human health (Wendelboe-Nelson et al., 2019). Thus, people have been visiting forests for recreation and relaxation, as well as for health benefits such as stress reduction (Korea Forest Service, 2020).
In response to this demand, in March 2010, the Korea Forest Service partially amended the Forestry Culture and Recreation Act (hereinafter referred to as the “Forest Recreation Act”) (Act No. 10116) and defined a “healing forest” as a forest that is developed for the utilization of a variety of elements of the forest, including fragrance and scenic view, in order to raise the immunity level of human bodies and enhance health, thereby establishing a legal basis for forest therapy (also known as forest healing). In July 2011, the Forest Recreation Act was partially amended (Act No. 10845) to legally define “forest therapy”, establish a system for training “forest healing instructors”, who are experts in developing and providing forest healing programs, and prepare standards for “forest healing programs” to effectively utilize the therapeutic functions of forests. As of 2022, 2,510 forest healing instructors have been trained (Korea Forest Welfare Institute, 2022). They are deployed in natural recreation forests, forest baths, healing forests, and forest paths to develop and disseminate various forest therapy programs.
A forest therapy program comprises activities that promote human health by utilizing various natural elements to maximize the therapeutic function of the forest (Kim, 2015). Therefore, the first step in the program development process should consider the gender, age, occupational characteristics, diseases, and purpose of the visit, and the program should be developed based on forest healing factors and therapies to maximize their effects (Yoo, 2009). However, the development and dissemination of customized forest therapy programs that consider user characteristics are insufficient, and extensive reviews and guidelines for target persons and applied therapies are needed (Lee et al., 2015).
As the demographic targeted for forest therapy broadens to encompass various fields, the scope of associated research is likewise expanding (Korea Forest Service, 2022). In order to present the health and medical effects of forest therapies for different groups of people, it is necessary to conduct research supported by systematic and scientifically produced evidence. Accordingly, many quantitative studies related to forest therapy programs have been conducted in South Korea, employing objective effectiveness verification aligned with evidence-based medicine principles. To ensure medical safety and the reliability of clinical outcomes, it is necessary to accumulate and socially disseminate research results on the effectiveness of forest therapies by targeting people and diseases (Yoo et al., 2015).
We reviewed the studies that comprehensively examined the effectiveness of forest therapy programs for each category of target people and found that Park (2020) focused on children, Yi and An (2021) on adults, and Lee (2022) on the elderly. In terms of patient category, Lee et al. (2016) focused on atopic children, while Chae and Lee (2020) focused on adult patients. Based on the results, we observed that the effectiveness of forest therapy programs was mainly examined in the healthy general population. However, despite the wide range of target participants in forest therapy programs, studies that examine the current status of populations in forest therapy programs and the effectiveness of forest therapy programs based on the situations and specific diseases of study populations are lacking.
Therefore, if we identified research trends and the status of study subjects by reviewing the previous studies on forest therapy programs, the results can be used as a basis for setting the direction for future studies on forest therapy programs for each target category. Furthermore, identifying the characteristics of programs organized by disease type can be used to develop target-specific forest therapy programs.
In this study, we systematically gathered forest therapy program studies conducted to date with the aim of identifying research characteristics (such as year and type of publication, and study subjects) and examining program features (including site type, implemented season, schedule type, and structure) based on disease type.
Research Methods
Research design
We used the scoping review research methodology to examine the research characteristics and program characteristics of papers on forest therapy programs by disease type. This methodology delineates the characteristics and extent of evidence within a specific area, providing guidance for subsequent research. Moreover, it functions to assess the existing research landscape of a particular topic and field, often serving as a preliminary study preceding a systematic review(Arksey and O’Malley, 2005; Seo, 2020). We conducted the study by following the five-stage research procedure suggested by Arksey and O’Malley (2005).
Data collection
In this study, the scoping review comprised five stages: 1) identifying the research questions, 2) identifying relevant studies, 3) study selection, 4) charting the data, and 5) collating, summarizing, and reporting results. We conducted the study in accordance with the recommendations suggested for each step.
Stage 1: Identifying the research questions
In this study, we used the PCC (Population, Concept, and Context) framework (Peters et a l., 2015). The research questions were chosen by selecting study subjects corresponding to the 8th Korean Standard Classification of Diseases (KCD-8) for the population, forest therapy programs for the concept, and the scope of papers in the field of forest therapy for the context. The research questions are as follows: “What diseases do forest therapy programs focus on?” and “How do forest therapy programs operate?” To examine the study populations, we excluded healthy individuals according to the KCD-8 (Korean Standard Classification of Diseases, 2022) and examined the operation methods of forest therapy programs (implemented site, season, type, cycle, number of sessions, and duration) to characterize them by disease type.
Stage 2: Identifying relevant studies
To identify the diseases addressed by forest therapy program interventions in existing research, this study considered papers published up to March 31, 2022, without restricting the publication year. The literature search was conducted from April 1 to April 5, 2022, mainly using online databases. The Korean online databases used for the literature search were RISS, KISS, Science ON, DBpia, and the National Assembly Digital Library, and the international online databases were SCOPUS, PubMed, MEDLINE, and EMBASE. The search keywords we selected were “Forest”, “Greenspace”, “Experience”, “Activity”, “Therapy”, “Healing”, “Shinrin-yoku”, “Exercise”, “Program”. This was to search for studies related to forest therapy programs comprehensively and select papers by disease type in order to obtain comprehensive search results.
Stage 3: Study selection
Based on the recommendations of the scoping review, three researchers (lead author, a professor in forest therapy, and a Ph.D. in forest therapy) held a meeting to select the inclusion and exclusion criteria for study selection. Studies were selected by reviewing the titles and abstracts of the retrieved papers, followed by reviewing the full-text files of the selected studies to make the final selection. The inclusion criteria for studies were (1) experimental studies including pre-post intervention measures of physical or mental health outcomes, (2) intervention of structured forest therapy programs, (3) published in English or Korean. Exclusion criteria were (1) studies targeting healthy individuals or animals, (2) intervention of unstructured simple forest therapy activities, (3) no results presented, (4) no full-text files, and (5) duplication between academic papers and theses/dissertations.
During the process, disagreements on study selection were resolved through meetings. A total of 21,215 articles were retrieved from the aforementioned South Korean and international databases. We excluded 9,910 articles that were not theses, dissertations, and academic papers, articles not written in English or Korean, and articles that did not contain full text. In addition, we excluded 4,546 duplicate papers and 137 conference papers. Subsequently, we also excluded 5,919 papers unrelated to forest therapy, 309 papers without descriptions of experimental studies, 229 papers that examined the general population or animals, 29 papers that conducted simple intervention activities rather than programs, and 18 papers that showed duplication between academic papers and theses/dissertations. As a result, we finally selected 118 papers (see Fig. 1).
PRISMA flow chart.
Stage 4: Charting the data
We used the Microsoft Excel program to organize the data in the selected papers. In order to extract data that met the research criteria set for this study, three researchers convened meeting to create a research framework according to the recommendations of the scoping review. The scope of data extraction for the scoping review can be divided into the following categories: authors, publication year, study location, intervention type, study population, study aims, overview of methods, outcomes measures, and results (Armstrong et al., 2011). In this study, data were extracted by dividing them into study characteristics (authors, year of publication, type of publication, study population) and program characteristics (site type, duration, structure) according to the aims of the study, referring to previous studies on forest therapy programs. To identify the characteristics of the study subjects, we examined the characteristics of the study populations presented in the title and text of the papers, and if the information was not specific, we additionally identified the diseases of the study subjects by examining the text. Based on the identified characteristics of the study subjects, disease codes were applied based on the KCD-8, which were then reviewed by nursing and health-related experts. When applying disease codes, we assigned only one disease code to each independent experimental group, and even if an experimental group included multiple diseases, we used just one parent disease code.
Results and Discussion
Characteristics of studies
Year of publication and type of publication
Table 1 shows the year of publication and the type of publication for 118 selected papers. Publication years range from 1996 to 2022, with a notable increase in publications after 2011, peaking at 17 papers (14.4%) in 2017. Based on the publication type, 49 (41.5%) were academic articles, 31 (26.3%) were master’s theses, and 19 (16.1%) were doctoral dissertations in the case of the finally selected South Korean papers. In the case of the foreign papers, 19 (16.1%) were academic articles.
Frequency by publication year and type of selected articles
Study subjects
KCD codes for study subjects
The KCD codes applied to the study subjects in the selected articles included main-category codes and 131 sub-category codes. Based on the main category, the KCD codes applied in the papers included “Factors influencing health status and contact with health services (Z00-Z99)” in 67 papers (51.1%), “Mental and behavioral disorders (F00-F99)” in 44 papers (33.6%), and 7 other main-category codes (see Table 2).
Frequency by main-category and sub-category KCD codes
Disease categorization based on KCD codes
To compare the characteristics of forest therapy programs by disease type, we classified them into health clients, mental health patients, and physical patients based on the applied KCD codes as shown in Table 3. Health clients are those corresponding to include those who have reasons to contact health services, even if they are not currently disease. Mental health patients include those diagnosed with psychiatric medical conditions, and “Codes for special purposes (U00-U99)”, which include patients with Repressed fire disorder. Physical patients encompass individuals with ailments that may manifest in various bodily systems and anatomical regions.
Disease categorization criteria based on main-category KCD codes
Characteristics of forest therapy programs in papers
Site types of forest therapy programs
Table 4 shows the frequency of forest therapy programs by site type. If there were more than two program sites, the frequency of each site was added separately. In the end, 16 site types were derived. When we examined the prevalence of primary study sites, the general forest type showed the highest frequency (n = 58, 39.2%), followed by forest welfare facilities (n = 48, 32.4%). When examined by disease type, for health clients, the frequency for each main type of study site was 31 (38.3%) for general forests, followed by 29 (35.8%) for forest welfare facilities. For mental health patients, the general forest type showed the highest frequency (n = 24, 50.0%). The main site types identified for physical patients showed that forest welfare facilities had the highest frequency (n = 10, 52.6%).
Frequency of each forest therapy program site
Seasons of forest therapy programs
Table 5 shows the frequency of each season in which the forest therapy programs were conducted. When seasons were consecutively classified, each was considered as one, and their frequencies were added accordingly. Overall, summer showed the highest frequency (n = 79, 39.9%), followed by fall (n = 53, 26.8%), spring (n = 53, 26.8%), and winter (n = 13, 6.5%).
Frequency of each forest therapy program season
Forest therapy program schedule types
We classified the forest therapy program types according to their schedule, as shown in Table 6: one-day, one-day multiple session, lodging, and lodging and multiple session types. If multiple types of programs were conducted in the study, each was added with its frequency. Overall, the one-day-multiple session type showed the highest frequency (n = 73, 54.9%), followed by the lodging type (n = 51, 38.3%). For mental health patients, the lodging type showed the highest frequency (n = 35, 74.4%).
Frequency of forest therapy program schedule type
Program structure by forest therapy program schedule type
Lengths of one-day type forest therapy programs
The frequency was reviewed and summarized for each duration of one-day type forest therapy programs, as shown in Table 7. The duration of 120 minutes showed the highest frequency (n = 27, 33.7%), followed by 60 min (n = 8, 10.0%). Overall, regardless of disease type, the duration of 120 min had the highest frequency.
Frequency of the duration of one-day type forest therapy programs
Duration of lodging type forest therapy programs
In Table 8, we have summarized the frequency for different durations of lodging type forest therapy programs. If multiple types of lodging programs were conducted in the study, each was added with its frequency. The results show that 3 days and 2 nights had the highest frequency (n = 26, 46.4%), followed by 2 days and 1 night (n = 18, 32.2%). When characterized by disease type, for health clients, 2 days and 1 night had the highest frequency (n = 16, 43.3%), followed by 3 days and 2 nights (n = 14, 37.8%). For mental health patients and physical patients, 3 days and 2 nights showed the highest frequency.
Frequency of the duration of lodging-type forest therapy programs
Cycles of session type forest therapy programs
Table 9 shows the results of examining the frequency of different cycles of session type forest therapy programs. The once-a-week cycle showed the highest frequency (n = 47, 61.9%), followed by twice a week (n = 12, 15.8%). When characterized by disease type, the once-a-week cycle showed the highest frequency in every type.
Frequency by cycle of session-type forest therapy program
Number of sessions in session type forest therapy programs
We have examined the frequency based on the number of sessions in each session type forest therapy program and summarized the results based on five-session units, as shown in Table 10. If multiple types of session programs were conducted in the study, the frequency of each was added. Overall, 6 to 10 session programs had the highest frequency (n = 34, 43.6%), followed by 2 to 5 session programs (n = 16, 20.5%), and 11 to 15 session programs (n = 15, 19.2%). When analyzed by disease type, 6 to 10 session programs showed the highest frequency in all disease types. For mental health patients, there is a wide distribution ranging from 2 to 30 session programs.
Frequency by number of sessions in session type forest therapy programs
Conclusion
In this study, we systematically collected forest therapy program studies using the scoping review methodology to analyze research trends and the status of study subjects and examine the characteristics of forest therapy programs by disease type.
Upon examining the research trends, we found that the number of academic papers has been steadily increasing in South Korea since 2006, starting with the first study in 1996. In particular, since 2011, the number of academic papers and theses has increased dramatically in South Korea, accounting for the majority of the total research. This finding can be attributed to the fact that in 2006, forestry and medical experts established the Korea Forest Healing Forum through interdisciplinary cooperation to explore ways of utilizing the healing functions of forests (Yeom, 2009), followed by developing of healing forests and disseminating forest therapy programs under the leadership of the Korea Forest Service in 2007, leading to their popularization. Since then, forest therapy has been introduced as a legal concept through a partial revision of the Forest Recreation Act in 2011, and policy conditions have been set, including “the active implementation of forest therapy programs to improve public health.” Furthermore, studies confirming the medical effects of forest therapy have been conducted actively through the establishment of forest therapy-related majors in regular university courses in 2010 (Chungbuk National University, 2024). In the case of studies in other countries, the number of publications has been steadily increasing since 2015. Therefore, evidence-based research should be continuously expanded by establishing policy conditions appropriate to the current situation, such as the enactment of independent forest therapy-related laws and the preparation of plans to implement forest therapy actively. This will contribute to disseminating the effectiveness of forest therapy within society and establish a foundation for collaboration with the health and medical sectors, fostering the international promotion of forest therapy.
Upon examining the study subjects from the selected papers, we found that the main subjects were health clients. Specifically, they included workers such as teachers, counselors, social welfare and mental health workers, and healthcare workers, as well as those who were socially vulnerable and exposed to stressful situations, such as young individuals in child welfare facilities, individuals with an addiction to the internet and smartphones, and families of patients. The second main group was mental health patients, including children with intellectual, developmental, and speech disabilities, as well as individuals with depression. The last group comprised physical patients, including menopausal women and patients with cancer patients and atopic dermatitis. This suggests that forest therapy has been utilized as part of preventive medicine and alternative therapies for unhealthy conditions attributed to lifestyle and environmental stress (Korea Forest Service, 2022), and studies have been conducted to identify the medical effects of forest therapy on patients. The relationship of diseases with certain occupations, caregiver roles, and social circumstances such as poverty has been reported (Wilhelm et al., 2004; Kuruvilla and Jacob, 2007). Moreover, individuals in socioeconomically and psychosocially disadvantaged situations have higher levels of stress than the general population and higher morbidity rates for depression and other diseases (Korean Women’s Development Institute, 2010). Therefore, there is a need to analyze the effectiveness of forest therapy programs comprehensively through systematic literature reviews and meta-analyses of forest therapy programs for health clients who are the main target. In the case of mental health and physical patients, this study shows similar results as a study by Park et al. (2012), in which a Delphi survey was conducted among experts in the fields of forestry and medicine to identify diseases suitable for forest therapy; however, there is a lack of research on this topic. The lack of research can be attributed to limitations in the process of recruiting special study subjects, namely patients, without cooperation from the health and medical fields. Therefore, it is necessary to continue to expand effectiveness research on patients through collaboration with the healthcare and medical sectors.
The sites of forest therapy programs primarily included general forests and forest welfare facilities. In addition, such programs were conducted in various locations such as parks, urban forests, university research forests, and national parks, and differences in the locations depending on the type of disease were noted. It is believed that nature recreation forests (Korea Forest Service, 2015a), healing forests (Korea Forest Service, 2015b), and other forest welfare facilities consider Barrier-Free design and Universal Design elements in their facility construction, making them suitable as forest therapy activity sites for health clients and individuals with physical patients in terms of safety. The effects of forest therapy may vary depending on the type of forest space (Kim, 2012). However, while most studies have conducted an overall analysis of available forest therapy resources, forest environments, forest compositions, and climatic conditions, etc., at the study sites, there has been a lack of discussion on the correlation between research subjects and forest environments. Therefore, research should be conducted on the appropriate forest therapy environment according to the characteristics of the subjects, and studies are needed to determine the correlation between the types of sites and the subjects.
In terms of the implemented seasons, summer accounted for the highest proportion overall, and spring and fall had similar proportions. This is likely due to the fact that spring, summer, and fall are considered for outdoor activities. These results are consistent with the findings of Park et al. (2021), who analyzed a forest therapy program operated by the Korea Forest Welfare Institute. South Korea has four distinct seasons due to its geographical characteristics (Lee, 1979), thus showing diverse ecological characteristics of the forest environment. Due to these characteristics, the concentration of non-volatile organic compounds in the forest environment varies depending on the season (Park et al., 2018), and diverse scenic views of forests are recorded in different seasons, eliciting psychological and physiological recovery effects (Chen et al., 2023; Kim and Lee, 2023). Specifically, winter has been associated with decreases in human physical fitness and activity levels (Shephard and Aoyagi, 2009), as well as reductions in serum BDNF levels (Molendijk et al., 2012), and increased rates of diagnosis for depression and anxiety (Winthorst et al., 2011). However, despite research on the impact of winter forest environments on human recovery, studies on winter forest therapy programs have been lacking (Bielinis et al., 2018a; Bielinis et al., 2018b; Bielinis et al., 2021; Peterfalvi et al., 2021). Therefore, it is necessary to conduct research to verify the effectiveness based on the characteristics of forest therapy resources existing in each season, and research on forest therapy programs utilizing winter forest environments needs to be expanded.
Upon scrutinizing the structures of forest therapy programs, we noted that the primary types of schedules included one-day multiple session type and lodging type. For the one-day type programs, 120 min showed the highest frequency, followed by 60 min, and 180 min. The lodging type programs were mainly 3 days and 2 nights programs and 2 days and 1 night programs, and the session type programs were mainly based on a once-a-week cycle, with 6 to 10 sessions. In particular, one-day multiple session type programs predominated among mental health patients (74.4%), with programs of 16 sessions or more being attempted. It is interpreted that such programs aim to provide repetitive and long-term interventions for mental health patients. Generally, it has been reported that the effectiveness of forest therapy varies depending on program schedules, lengths, durations, cycles, and sessions (Cho, 2019; Kwon, 2023), and greater changes and effectiveness can be observed when participation is continuous (Yeon, 2007; Kim and Jeon, 2019). However, there has been a lack of discussion on the correlation between the characteristics of subjects and forest therapy program attributes. Therefore, it is necessary to expand the research on various types and schedules of forest therapy programs, in addition to the ones that are currently being studied, and to verify the appropriate program structures according to the type of disease. This will allow for more options and appropriate structures when developing forest therapy programs for specific populations.
This study applied the scoping review methodology to extensively review the studies on forest therapy programs conducted to date and provided an overview of the research characteristics and program characteristics in the selected papers. This study is significant in that we have suggested the study subjects of forest therapy programs objectively by summarizing them according to the KCD-8 and identifying the scope of research conducted to date. We hope that this study serves as a reference for developing target-specific forest therapy programs in the future by segmenting the targets according to their characteristics and collaborating with the stakeholders in the healthcare and medical fields. Nevertheless, it is essential to acknowledge a limitation in this study, as it relies on a literature review, which might introduce potential gaps in the research results. Therefore, it is necessary to review more cases of forest therapy programs and current program data of public and private forest therapy organizations to analyze and summarize the results more broadly. This will contribute to the discussion on the relationship between diseases and forest therapy programs.
