SYSTEMATIC REVIEW article
Sec. Environmental Psychology
Volume 14 - 2023 | https://doi.org/10.3389/fpsyg.2023.1086121
Horticultural therapy for stress reduction: A systematic review and meta-analysis
- 1Department of Landscape Architecture, College of Horticulture, China Agricultural University, Beijing, China
- 2Faculty of Architecture, Building and Planning, Melbourne School of Design, University of Melbourne, Parkville, VIC, Australia
Introduction: Horticultural therapy has been increasingly accepted as a non-pharmacological stress reduction treatment. Previous studies have demonstrated its therapeutic effects, with the effect varying according to the populations, settings, and interventions of horticultural therapy. This study aimed to provide a comprehensive review of the current literature regarding the effectiveness of horticultural therapy in reducing stress.
Methods: We selected databases including PubMed, Cochrane Library, Embase, Web of Science, China National Knowledge Infrastructure, and VIP Data as our data source, and the original search was completed in January 2023.
Results: Our results showed significantly increased effects of horticultural therapy on psychological indicators compared to a control group, but an insignificant effect on physiology indicators. The result of the subgroup analysis demonstrated that the stress-reducing effects of horticultural therapy were related to the characteristics of the population and indoor and virtual areas were the most effective setting for horticultural therapy. At the same time, a total duration of 100–500 minutes provided better effects of stress reduction.
Discussion: We also developed a theoretical framework based on a “Participants-Settings-Interventions” structure for horticulture therapy in terms of its stress-reduction effects, to provide a reference for future horticultural therapy activities.
With the ongoing trend of urbanization, more than two-thirds of the world's population is expected to live in cities and towns by 2050 (Montgomery, 2007). In the same time frame, there is an increasing number of people suffering from stress-related issues (Dye, 2008). In fact, stress-related mental health issues such as depression and anxiety will become more prevalent by 2030, according to the World Health Organization (World Health Assembly, 2012). Individual stress can ultimately reduce the productivity and general wellbeing of society as a whole (Vinokur and Caplan, 1986), at the same time increasing the burden on the government's investment in public health (Greenberg et al., 1999; Ho et al., 2013).
Stress-related issues have always been a major focus of medical and psychological research. There are many stress-inducing factors, including an actual or perceived threat to an organism, which is referred to as the “stressor” (Schneiderman et al., 2005). Stressors typically include personal difficulties (e.g., conflict with loved ones, being alone, lack of income, worries about the future), problems at work (e.g., conflict with colleagues, an extremely demanding or insecure job), or major threats in the community (e.g., violence, disease, lack of economic opportunity) (World Health Organization, 2020). The response to stressors is known as “stress response”, an adaptive mobilization of the organism to cope with potentially negative situations (Kaplan, 1995) and any effects that seriously threaten homeostasis (Selye, 1978). It could be linked to vascular (Katsarou et al., 2013), neurological (Busciglio et al., 1998), autoimmune (Stojanovich and Marisavljevich, 2008), cardiovascular (Esch et al., 2002; Pogosova, 2007), inflammatory illness (LeResche and Dworkin, 2002), and other disorders, and might lead to the aggravation of diabetes (Wellen and Hotamisligil, 2005) and asthma (Ohno, 2017). The unprecedented stress caused by social isolation from the COVID-19 pandemic has been proven to lead to anxiety and depression (Santomauro et al., 2021). Therefore, there is an urgent need for appropriate methods to address stress-related problems.
Horticultural therapy has been increasingly embraced as a non-pharmacological stress reduction treatment due to its flexibility and free of side effects. Horticultural therapy encourages people to spend time in nature, which has been shown to have stress-relieving and attention-restoring effects, based on the Stress Recovery Theory (SRT) (Ulrich et al., 1991) and the Attention Restoration Theory (ART) (Kaplan, 1995). In recent decades, researchers and health practitioners have placed greater focus on the possible stress-reduction benefits of horticultural therapy and activities.
These studies have reached inconsistent conclusions, with some studies showing significant effects of horticultural therapy on reducing people's stress levels (Pálsdóttir et al., 2013; Han et al., 2018; Lee et al., 2018b) and others showing non-significant effects (Tu et al., 2020; Wei et al., 2020; Chalmin-Pui et al., 2021). A meta-analysis can synthesize new findings convincingly from previous studies on the same topic (Glass, 1977), while many of the current literature reviews are topic-specific [cognitive function (Tu and Chiu, 2020), depressive symptoms (Zhang et al., 2022), and psychosocial wellbeing (Spano et al., 2020)] or population-specific [the elderly (Wang et al., 2022), people with dementia (Zhao et al., 2020), and people with schizophrenia (Lu et al., 2021)]. Besides, given that differences in the study population, interventions of horticultural therapy, and environmental settings could affect the effectiveness, subgroup analysis is needed for the effect of stress reduction in these areas, which as far as we know has not been addressed in current literature reviews. Therefore, our study included studies with all stress-related physiological and psychological indicators and assessed the stress-reduction effects using a meta-analysis as well as a further subgroup analysis to provide a comprehensive picture of the stress-reduction effects of horticultural therapy.
The aims of this study are to (1) identify the physiological and psychological impacts of horticultural therapy on stress reduction; (2) compare the impact of different groups of people; (3) evaluate the impact of various environmental settings; (4) evaluate the impact of various types of intervention. At the same time, we contrived to develop a theoretical framework that could further serve as a reference for future research as well as our efforts in stress-reduction-related horticultural therapy programs.
This quantitative systematic review with meta-analysis was conducted based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (Moher et al., 2009). PRISMA checklist is presented in Appendix A.
2.1. Search strategy
We searched relevant studies in six electronic bibliographic databases including PubMed, Cochrane Library, Embase, Web of Science, China National Knowledge Infrastructure, and VIP Data. The search was undertaken by combining search terms for horticultural therapy and stress, with multiple synonymous terms, such as “gardening” and “pressure”. All databases were searched from inception to January 2023. Detailed search steps are presented in Appendix B.
2.2. Inclusion criteria and exclusion criteria
Table 1 outlines the inclusion/exclusion criteria, according to the population, intervention, comparison, outcomes, and study design (PICOS).
Studies normally utilized physiological and psychological indicators to assess the outcomes of stress-reduction effects. Physiological indicators typically include blood pressure (systolic blood pressure and diastolic blood pressure), pulse pressure, saliva cortisol levels, salivary α-amylase (sAA), pulse rate (BPM), heart rate variability (HRV), electroencephalography (EEG), skin conductance (SC), skin temperature (SKT), facial thermal imaging, etc. Psychological indicators were mainly assessed by standardized tests including the Perceived Stress Scale (PSS), the Stress and Crisis Inventory (SCI-93), the Stress Response Scale (SRS-18), the Depression Anxiety Stress Scale (DASS21), the Labor Occupational Pressure Scale, the Geriatric Depression Scale (GDS-30), the Psychosocial wellbeing Index Short Form (PWI-SF), 4T-PROs-Stress, Rehabilitation Stress Scales, etc.
2.3. Study selection, data extraction and analysis
We imported all studies into EndNote X8. Two independent reviewers assessed the studies based on the inclusion and exclusion criteria after removing duplicate studies. A third reviewer would be brought in when two independent reviewers had divergent opinions.
We first read the title and abstract of each study, followed by a full-text screening work to decide if it should be included in the analysis. We extracted the following information from each study: (1) basic information, including the research title, first author, and publication year; (2) basic characteristics of the research subjects, including the sample size, age, and gender distribution of people included in each group; (3) details of intervention of horticultural therapy, including intervention activities, duration and settings; (4) critical elements of bias risk assessment; and (5) the outcome indicators.
We pooled the information of the individual studies in Revman5.4 software and R 4.0.3 (R Core Team, 2020) using the “meta” package. Researchers employed a random-effects model to account for study heterogeneity and effect sizes. We employed standardized mean differences (SMDs) because of the various indicators of the stress-relieving outcomes adopted in different studies. The data was compiled using 95 % confidence intervals (CIs). We employed standard I2 tests to measure statistical heterogeneity, and we ran a sensitivity analysis to assess the reproducibility and stability of the results. Forest plots were used to visualize the results. Funnel plots were created to visually evaluate publication bias, while Egger's regression test was used to statistically evaluate publication bias.
We also used subgroup analysis to investigate the effects of differences in participants, environmental settings, and interventions of horticultural therapy, accounting for a total of 11 subgroups. As for the participant-related subgroups, we coded their stressors (from education vs. occupation vs. rehabilitation), age, gender, and nationality. The subgroup of environmental settings was coded as indoor, outdoor, combined, and virtual settings. We then categorized the outdoor settings into therapeutically and non-therapeutically designed environments based on the aims and intentions of the design, and we also divided the outdoor settings into farms, gardens, campus, and parks in which horticultural therapy was carried out, to further investigate which kind of outdoor environment could be more effective in stress reduction. We coded the intervention-related subgroups according to the types of activities, duration, frequency, and course. This facilitates researchers and practitioners in developing more effective activities for horticultural therapy.
2.4. Risk of bias assessment
Two independent reviewers critically assessed the quality of the eligible studies. To assess the risk of bias in the included studies with RCT designs, we utilized the RCT-specific bias risk assessment tool in the Cochrane handbook for systematic reviews of treatment (Higgins et al., 2011), which assesses randomization procedure biases, allocation concealment, and selective reporting. We used the Joanna Briggs Institute (JBI) critical appraisal tools to assess studies with quasi-experimental designs.
3.1. Study selection
Figure 1 outlines the evaluation procedure. We originally yielded a total of 11,383 articles from PubMed (n = 269), Embase (n = 1,342), Cochrane Library (n = 8), Web of Science (n = 9,150), China National Knowledge Infrastructure (n = 441), and VIP Data (n = 173). Five hundred sixty-one articles were eliminated due to duplication, and 10,698 were removed after screening the titles and abstracts. Of the remaining 124 studies, 17 were removed because the full text was not available, 63 because they lacked comprehensive data, four because they were off-topic, and one because it was not in English or Chinese. Eight studies were further removed because the outcome indicators were irrelevant to stress reduction and detailed reasons are presented in Appendix C. There were 31 studies included in our final analysis (Kam and Siu, 2010; Gonzalez et al., 2011; Hawkins et al., 2011; Van Den Berg and Custers, 2011; Pálsdóttir et al., 2013; Chen et al., 2015; Lee et al., 2015, 2018a,b, 2022; Dewi et al., 2017; Huang et al., 2017; Park et al., 2017a,b; Han et al., 2018; Hassan et al., 2019; Shao et al., 2020; Siu et al., 2020; Tao et al., 2020, 2022; Tu et al., 2020; Wei et al., 2020; Chalmin-Pui et al., 2021; Gong and Chen, 2021; Kim et al., 2021; Meore et al., 2021; Szczepańska-Gieracha et al., 2021; Chan et al., 2022; Curzio et al., 2022; Du et al., 2022; Odeh et al., 2022).
3.2. Characteristics of the studies
Appendix D summarizes the characteristics of the studies included in our analysis, of which 21 were quasi-experimental studies and 10 were randomized controlled trials. The reported studies were published between 2010 and 2022, with slightly more articles published in 2020 (n = 5), 2021 (n = 5) and 2022 (n = 6). The sample size ranged from 8 to 113 (1,036 in total). Experimental and control group activities, detailed settings and performers are presented in Appendix E.
The participants' ages ranged from 7 to 93 years. In the case of gender, most studies involved both male and female participants, with two studies only involving males and seven only females. Furthermore, the various studies were conducted in 10 countries, with the majority in Asia (22 studies, 13 in China, seven in Korea, and two in Japan), followed by Europe (seven studies, two in the UK and one each in Italy, Sweden, the Netherlands, Poland, and Norway), with two study from North America (the USA). Most reported studies did not identify the stressors, except that one study identified participants' stressors from rehabilitation, two studies from education, and two studies from occupation.
Fourteen studies conducted the intervention of horticultural therapy in indoor settings, 11 in outdoor settings (three in farms, six in gardens, one in campus and one in parks), four in a combination of indoor and outdoor settings, and one involved virtual reality. One study did not mention the settings.
The interventions of horticultural therapy, mainly refer to horticultural activities in this analysis, including transferring plants, tasting and smelling, handcrafting activities, flower arrangement, transplanting plants, potting activities, soil-mixing activities, harvesting activities, planting and sowing activities, walking and meditation. The intervention also differed in terms of duration (three minntes to 210 min), total duration (3–10,080 min), and frequency (two to three times a month to four times a week).
3.3. Risk of bias
Allocation concealment and outcome assessment blinding were rated as unclear risks, whereas five studies did not describe in detail the method of random sequence generation and six studies had instances of participation withdrawal due to incomplete outcome data. The majority of studies were found to be of low risk of bias. We followed the JBI critical appraisal checklist to assess the quasi-experimental studies involved. Figure 2 shows the results of the risk evaluation.
3.4. Meta-analysis outcomes
Thirteen quasi-experimental studies and five studies with RCT designs were adopting physiological indicators to assess the stress-reduction effects, while ten quasi-experimental studies and six studies with RCT designs adopted psychological indicators. Therefore, we used SMDs to manage the differences in measurements, and the meta-analysis was estimated under a random-effects model.
Figure 3 shows the effects on the physiology indicators, with the outcomes slightly varied (SMD = −0.10, 95% CI [−0.24, 0.03], p = 0.13, I2 = 83%) in terms of the influence of horticultural therapy on stress. We detected significant differences in the sensitivity analyses when removing (Tu et al., 2020) (SMD = −0.05, 95% CI [−0.15, 0.05], p = 0.33, I2 = 73%).
In comparison, the psychological effectiveness was more significant (SMD = −0.73, 95% CI [−0.91, −0.54], p < 0.0001, I2 = 44%), as shown in Figure 4. We removed all the studies included in this meta-analysis one by one. When the study of Meore et al. (2021) and Chan et al. (2022) was removed, the results showed that heterogeneity was reduced (SMD = −0.68, 95% CI [−0.86, −0.51], p < 0.0001, I2 = 35%; SMD = −0.68, 95% CI [−0.86, −0.50], p < 0.0001, I2 = 35%).
3.5. Subgroup analysis outcomes
We used subgroup analysis to investigate the effects of differences in participants, environmental settings, and interventions of horticultural therapy. Figure 5 shows the subgroup analysis outcomes.
Figure 5. (A) Results of participant-related subgroup analysis. (B) Results from setting-related subgroup analysis. (C) Results from intervention-related subgroup analysis.
Horticultural therapy efficiently lowered stress related to educational stressors (SMD = −0.79), compared to occupational and rehabilitation stressors (SMD = −0.58 and SMD = −0.72, respectively) in psychological indicators.
Males (SMD = −2.92) obtained better stress-relieving effects than females (SMD = −0.21) in physiological indicators.
Horticultural therapy was most effective in reducing stress in people aged over 60 (SMD = −0.18 in physiological indicators; SMD = −1.11 in psychological indicators), followed by people aged under 18 (SMD = −0.08 in physiological indicators; SMD = −0.79 in psychological indicators).
Participants from Asia had a better stress reduction experience in horticultural therapy (SMD = −0.14) in terms of physiological indicators, while participants from North America had a better stress reduction experience in terms of psychological indicators (SMD = −0.87).
The results confirmed that the indoor setting had the best decompression effect (SMD = −0.18) in terms of physiological indicators, while the virtual environment constituted the most effective in terms of psychological indicators (SMD = −1.11).
The results show that the non-therapeutically designed settings had a better decompression effect (SMD = −0.81) than therapeutically designed settings (SMD = −0.60). The garden settings were more effective in terms of psychological indicators (SMD = −3.82), while the farm settings were more effective in terms of physiological indicators (SMD = −0.23).
126.96.36.199. Type of activities
We included 10 studies in the activity-specific subgroup analysis, among which five reported studies involved multiple horticultural activities as interventions (Lee et al., 2018b; Tu et al., 2020; Wei et al., 2020; Gong and Chen, 2021; Kim et al., 2021), and seven studies involved single horticultural activity as interventions (Van Den Berg and Custers, 2011; Lee et al., 2015; Park et al., 2017b; Hassan et al., 2019; Shao et al., 2020; Tao et al., 2020; Du et al., 2022). The results revealed that walking (SMD = −1.42), meditation (SMD = −1.30), transferring plants (SMD = −0.56), and tasting and smelling (SMD = −0.32) were more effective in reducing stress, while other types of activity had limited or no stress-relieving effect.
The results show that the decompression effect was independent of the times of the intervention (SMD = −0.12).
The once-a-week session was the most effective in terms of physiological indicators (SMD = −0.58), while the 2-to-3-times-a-month session was the most effective in psychological indicators (SMD = −1.87).
Physiological indicators showed a duration of 30–60 min is the most effective (SMD = −0.34); in comparison, psychological indicators showed a duration of fewer than 30 min is the most effective (SMD = −1.11).
188.8.131.52. Total duration
The total duration of 100–500 min is the most effective in both physiological (SMD = −0.99) and psychological indicators (SMD = −0.80).
3.6. Results of publication bias
Funnel plots were created to visually evaluate publication bias. The funnel plot showed an approximate symmetrical distribution of study effect size, which suggests that there might not be any publication bias (Figure 6). Furthermore, Egger's regression test was used to statistically evaluate publication bias. The bias coefficient of Egger's test was < 0.0001, so there was a possibility of publication bias.
4.1. Participants' stressors and characteristics
Stress is often linked to complicated stressors (Chauhan et al., 2015), such as individual factors, relationship characteristics, health, work and education, community, finances, and the environment (Brannen et al., 2009). There was a limited number of studies identifying participants' stressors. Future research with clearly defined stressors is needed to develop stress reduction strategies for specific stressors and to improve the practice of horticulture therapy. Gender, ethnicity, and age have an impact on people's stressors and stress levels.
People with educational stressors obtained better stress reduction benefits in horticultural therapy activities. These activities transferred students' focus from daily stressful situations to plants, allowing them to experience happy feelings (Oh et al., 2020).
Males obtained better stress-relieving effects than females. Our results were consistent with other empirical studies that the self-esteem levels and emotional state of males increased more significantly than females after green exercise (Barton and Pretty, 2010). Females consider stressors as more threatening (Ptacek et al., 1992) and adopt more emotion-focused responses compared to males (Matud, 2004), making it more difficult to benefit from the stress-relieving effects of horticultural therapy.
People of different ethnic groups also differed in their level of stress (Wei et al., 2011; Hamamura and Laird, 2014) as well as their stress management strategies (Lam and Zane, 2004; Sawaumi et al., 2015). This could explain the fact that better stress reduction on physiological indicators was achieved by Asian participants, while better stress reduction on psychological indicators was achieved by North American participants.
People over 60 years old obtained better stress-reduction benefits from horticultural therapy. Long-term stressors can be harmful to people's health, especially elderly people (Schneiderman et al., 2005; Hurst et al., 2013). A review found that horticulture therapy could improve the physical and psychological health of older persons, which is consistent with our findings (Lin et al., 2022). Gardening appears to activate many important protective mechanisms for active and healthy aging. Therefore, the elderly, particularly in nursing homes and retirement communities, could be provided with more opportunities for horticulture therapy.
4.2. Characteristics and selection of intervention settings
The settings for horticultural therapy were essential, and they also had an important influence on the therapeutic benefits (Huxmann, 2016). Our results suggested that indoor and virtual environments were more effective in stress reduction than outdoor settings, which might be somewhat inconsistent with previous studies. This is possible because indoor and virtual environments had a relatively homogeneous and quiet atmosphere which were not likely to be affected by other distracting factors (e.g., other people, other animals, weather, temperature, sun exposure, noise, etc.,) (Guo et al., 2020). In other studies, for example, Brooks and colleagues argue that actual and virtual nature interactions were both beneficial to moods, though actual nature interactions yielded better outcomes (Brooks et al., 2017). Therefore, we encourage people to connect with “First Nature” and “Second Nature” as much as possible. From a practical standpoint, we recommend environments with both indoor and outdoor attributes, especially considering people with limited mobility and weather conditions that prevent outdoor activities.
We found that conducting horticultural therapy activities in gardens had greater effects on psychological indicators. Many studies found that gardens were more suitable environments for stress reduction (Kohlleppel et al., 2002; Coventry and White, 2018; Ulrich et al., 2020) than parks and green views in terms of psychological health (Marques et al., 2021). Meanwhile, the high biodiversity of gardens had a huge benefit in increasing the stress-relieving impact (Keniger et al., 2013; Oh et al., 2020).
4.3. Characteristics and effectiveness of the interventions
The lack of direct comparisons between the various activities made it hard to verify whether one activity contributed to the reported effect (Murroni et al., 2021). This question has been answered in our subgroup analysis. Activities that activate the five senses, such as walking, meditation, transferring plants, and tasting and smelling were more effective. At the same time, it is important to consider the different intensities of activities for different groups of people when choosing the types of activity (Park et al., 2014; Lee et al., 2021), with a focus on low and medium-intensity activities.
It is also a key issue to determine the duration and frequency of horticultural therapy programs (Tu and Chiu, 2020). The 30–60 min session was more effective in physiology indicators and the < 30 min session was more effective in psychological indicators, which could achieve the stress-reduction goals and at the same time not make participants feel bored during the session. A total duration of 100–500 min could be more beneficial by maintaining the appeal and uniqueness while attracting people's attention and willingness to engage in the cyclical process of treatment.
4.4. A theoretical framework
Our findings supported the positive effect of horticultural therapy on stress reduction. Educational stressors achieved better results with horticultural therapy interventions. Seniors over 60 and males had a better stress reduction experience in horticultural therapy. Indoor and virtual areas were the most effective setting for horticultural therapy and we believed that a combination of outdoor and indoor areas was the optimal setting for horticultural therapy. At the same time, a total duration of 100–500 min provided better effects of stress reduction.
We developed a theoretical framework for horticulture therapy in terms of its stress-reduction effects on physiological and psychological indicators based on “Participants-Settings-Interventions” to provide a reference for future horticultural therapy activities (Table 2).
We also identified several limitations in this literature review. First, studies that were not published in English or Chinese were not included in this review and generalizability may be limited. Second, the lack of randomized controlled trials of high quality, though difficult to perform, also limited our outcomes. Only ten out of 31 reported studies were randomized controlled trials, let alone the participant withdrawal in several RCT studies. Finally, the number of articles in the study, the sample size of these articles, and the heterogeneity between studies would have affected the results of the subgroup analysis. Moreover, due to the lack of specific data in some of the included studies, we were unable to conduct a subgroup analysis of these studies.
Our meta-analysis found evidence of the beneficial effects of horticultural therapy on stress reduction. We developed a comprehensive theoretical framework that explains the design strategies for horticulture therapy activities in terms of the environmental settings and the interventions (types of activity, duration, frequency, and course) for diverse populations with varied stressors.
We have to pay more attention to the ongoing effect, especially when the program lasts for a longer period of time. Besides, future randomized controlled trials should clearly describe the blind evaluation, suitable follow-up duration, study size calculation, and basic descriptive statistics (e.g., means and standard deviations), all of which are essential for readers and follow-up research.
A comprehensive guide to the operation of horticultural therapy is needed in order to provide realistic therapeutic interventions with sufficient scientific value and clinical relevance. Our results contribute to addressing the question of how horticultural therapy activities can be organized to maximize the stress-relieving effects on different groups of people, to improve their physical and mental health as well as their quality of life.
Data availability statement
The original contributions presented in the study are included in the article/Supplementary material, further inquiries can be directed to the corresponding author.
SL: data curation and writing—original draft preparation. SL, FX, JL, and MX: writing—review and editing. FX: supervision. All authors have read and agreed to the published version of the manuscript.
This study was supported by the Beijing Municipal Science and Technology Commission (project no. Z201100008020004).
Conflict of interest
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.
The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fpsyg.2023.1086121/full#supplementary-material
Brannen, C., Emberly, D. J., and McGrath, P. (2009). Stress in rural Canada: a structured review of context, stress levels, and sources of stress. Health Place 15, 219–227. doi: 10.1016/j.healthplace.2008.05.001
Brooks, A. M., Ottley, K. M., Arbuthnott, K. D., and Sevigny, P. (2017). Nature-related mood effects: season and type of nature contact. J. Environ. Psychol. 54, 91–102. doi: 10.1016/j.jenvp.2017.10.004
Busciglio, J., Andersen, J. K., Schipper, H. M., Gilad, G. M., McCarty, R., Marzatico, F., et al. (1998). “Stress, aging, and neurodegenerative disorders—molecular mechanisms,” in Stress of Life: From Molecules to Man, ed. P. Csermely (New York: New York Acad Sciences), p. 429–443. doi: 10.1111/j.1749-6632.1998.tb09021.x
Chalmin-Pui, L. S., Roe, J., Griffiths, A., Smyth, N., Heaton, T., Clayden, A., et al. (2021). “It made me feel brighter in myself”—the health and well-being impacts of a residential front garden horticultural intervention. Landsc. Urban Plan. 205, 103958. doi: 10.1016/j.landurbplan.2020.103958
Chan, H-. S., Chu, H-. Y., and Chen, M-. F. (2022). Effect of horticultural activities on quality of life, perceived stress, and working memory of community-dwelling older adults. Geriatric Nursing 48, 303–314. doi: 10.1016/j.gerinurse.2022.10.016
Chauhan, E., Bali, A., Singh, N., and Jaggi, A. S. (2015). Cross stress adaptation: phenomenon of interactions between homotypic and heterotypic stressors. Life Sci. 137, 98–104. doi: 10.1016/j.lfs.2015.07.018
Chen, C-. Y., Wu, F-. J., Chen, C-. M., Hsu, H., and Koo, M. (2015). Effects of horticultural therapy activity programme for alleviating work-related stress and improving wellbeing of nursing staff. Taiwan Gardening 61, 281–291.
Curzio, O., Billeci, L., Belmonti, V., Colantonio, S., Cotrozzi, L., Pasquale, D. e. C. F., et al. (2022). Horticultural therapy may reduce psychological and physiological stress in adolescents with anorexia nervosa: a pilot study. Nutrients 14, 5198. doi: 10.3390/nu14245198
Dewi, N., Komatsuzaki, M., Yamakawa, Y., Takahashi, H., Shibanuma, S., Yasue, T., et al. (2017). Community gardens as health promoters: effects on mental and physical stress levels in adults with and without mental disabilities. Sustainability 9, 63. doi: 10.3390/su9010063
Du, J., Yin, J., Chen, X., Hassan, A., Fu, E., Li, X., et al. (2022). Electroencephalography (EEG)-based neural emotional response to flower arrangements (FAs) on normal elderly (NE) and cognitively impaired elderly (CIE). Int. J. Environ. Res. Public Health 19, 3971. doi: 10.3390/ijerph19073971
Gong, X., and Chen, L. (2021). A study on the effect of lnterventional horticultural therapy on residents' physical and mental health in forest botanical garden. J. Green Sci. Technol. 23, 1–5+35. doi: 10.16663/j.cnki.lskj.2021.11.002
Gonzalez, M. T., Hartig, T., Patil, G. G., Martinsen, E. W., and Kirkevold, M. (2011). A prospective study of group cohesiveness in therapeutic horticulture for clinical depression: therapeutic horticulture in depression. Int. J. Ment. Health Nurs. 20, 119–129. doi: 10.1111/j.1447-0349.2010.00689.x
Greenberg, P. E., Sisitsky, T., Kessler, R. C., Finkelstein, S. N., Berndt, E. R., Davidson, J. R. T., et al. (1999). The economic burden of anxiety disorders in the 1990s. J. Clin. Psychiatry 60, 427–435. doi: 10.4088/JCP.v60n0702
Guo, L-. N., Zhao, R-. L., Ren, A-. H., Niu, L-. X., and Zhang, Y-. L. (2020). Stress recovery of campus street trees as visual stimuli on graduate students in autumn. Int. J. Environ. Res. Public Health 17, 148. doi: 10.3390/ijerph17010148
Hamamura, T., and Laird, P. G. (2014). The effect of perfectionism and acculturative stress on levels of depression experienced by east Asian international students. J. Multicult. Couns. Devel. 42, 205–217. doi: 10.1002/j.2161-1912.2014.00055.x
Han, A-. R., Park, S-. A., and Ahn, B-. E. (2018). Reduced stress and improved physical functional ability in elderly with mental health problems following a horticultural therapy program. Complement. Ther. Med. 38, 19–23. doi: 10.1016/j.ctim.2018.03.011
Hassan, A., Tao, J., Bing, C. Q., Yinggao, L., Li, G., Jiang, M., et al. (2019). Better mind, better work: effects of plants on adolescent mental stress as measured by EEG. Hypertens. Res. 42, 1086–1088. doi: 10.1038/s41440-019-0209-7
Hawkins, J. L., Thirlaway, K. J., Backx, K., and Clayton, D. A. (2011). Allotment gardening and other leisure activities for stress reduction and healthy aging. Hortte 21, 577–585. doi: 10.21273/HORTTECH.21.5.577
Higgins, J. P. T., Altman, D. G., Gotzsche, P. C., Juni, P., Moher, D., Oxman, A. D., et al. (2011). The cochrane collaboration's tool for assessing risk of bias in randomised trials. BMJ 343, d5928–d5928. doi: 10.1136/bmj.d5928
Ho, R. C. M., Mak, K-. K., Chua, A. N. C., Ho, C. S. H., and Mak, A. (2013). The effect of severity of depressive disorder on economic burden in a university hospital in Singapore. Expert Rev. Pharmacoecon. Outcomes Res. 13, 549–559. doi: 10.1586/14737167.2013.815409
Huang, H., Lin, M., and Chen, W. (2017). Preliminary study of the benefits of horticultural therapy on family caregivers' perception of emotion and stress. Appl. Psychol. Res. 67. doi: 10.3966/156092512017120067002
Huxmann, N. J. (2016). “The garden as setting for horticultural therapy,” in Xxix International Horticultural Congress on Horticulture: Sustaining Lives, Livelihoods and Landscapes (ihc2014): Xii International People Plant Symposium: Horticulture and Human Communities, eds. S. A. Park, and E. Rappe (Leuven 1: Int Soc Horticultural Science), p. 39–45.
Kim, S-. O., Jeong, J-. E., Oh, Y-. A., Kim, H-. R., and Park, S-. A. (2021). Comparing concentration levels and emotional states of children using electroencephalography during horticultural and non-horticultural activities. Horts 56, 324–329. doi: 10.21273/HORTSCI15522-20
Lam, A. G., and Zane, N. W. S. (2004). Ethnic differences in coping with interpersonal stressors: a test of self-construals as cultural mediators. J. Cross Cult. Psychol. 35, 446–459. doi: 10.1177/0022022104266108
Lee, A-. Y., Kim, S-. O., and Park, S-. A. (2021). Attention and emotional states during horticultural activities of adults in 20s using electroencephalography: a pilot study. Sustainability 13, 12968. doi: 10.3390/su132312968
Lee, A-. Y., Park, S-. A., Park, H-. G., and Son, K-. C. (2018a). Determining the effects of a horticultural therapy program for improving the upper limb function and balance ability of stroke patients. Horts 53, 110–119. doi: 10.21273/HORTSCI12639-17
Lee, M. J., Oh, W., Jang, J. S., and Lee, J. Y. (2018b). A pilot study: Horticulture-related activities significantly reduce stress levels and salivary cortisol concentration of maladjusted elementary school children. Complement. Ther. Med. 37, 172–177. doi: 10.1016/j.ctim.2018.01.004
Lee, M. S., Lee, J., Park, B-. J., and Miyazaki, Y. (2015). Interaction with indoor plants may reduce psychological and physiological stress by suppressing autonomic nervous system activity in young adults: a randomized crossover study. J. Physiol. Anthropol. 34, 21. doi: 10.1186/s40101-015-0060-8
Lee, S-. M., Jang, H-. J., Yun, H-. K., Jung, Y-. B., and Hong, I-. K. (2022). Effect of apartment community garden program on sense of community and stress. Int. J. Environ. Res. Public Health 19, 708. doi: 10.3390/ijerph19020708
LeResche, L., and Dworkin, S. F. (2002). The role of stress in inflammatory disease, including periodontal disease: review of concepts and current findings. Periodontol. 30, 91–103. doi: 10.1034/j.1600-0757.2002.03009.x
Lin, Y., Lin, R., Liu, W., and Wu, W. (2022). Effectiveness of horticultural therapy on physical functioning and psychological health outcomes for older adults: a systematic review and meta-analysis. J. Clin. Nurs. 31, 2087–2099. doi: 10.1111/jocn.16095
Lu, S., Zhao, Y., Liu, J., Xu, F., and Wang, Z. (2021). Effectiveness of horticultural therapy in people with schizophrenia: a systematic review and meta-analysis. IJERPH 18, 964. doi: 10.3390/ijerph18030964
Marques, P., Silva, A. S., Quaresma, Y., Manna, L. R., Magalhaes Neto, d. e., Mazzoni, N., et al. (2021). Home gardens can be more important than other urban green infrastructure for mental wellbeing during COVID-19 pandemics. Urban Forestry Urban Green. 64, 127268. doi: 10.1016/j.ufug.2021.127268
Meore, A., Sun, S., Byma, L., Alter, S., Vitale, A., Podolak, E., et al. (2021). Pilot evaluation of horticultural therapy in improving overall wellness in veterans with history of suicidality. Complement. Ther. Med. 59, 102728. doi: 10.1016/j.ctim.2021.102728
Moher D. Liberati A. Tetzlaff J. Altman D. G. The Prisma Group (2009). Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement. PLoS Med. 6, e1000097. doi: 10.1371/journal.pmed.1000097
Murroni, V., Cavalli, R., Basso, A., Borella, E., Meneghetti, C., Melendugno, A., et al. (2021). Effectiveness of therapeutic gardens for people with dementia: a systematic review. Int. J. Environ. Res. Public Health 18, 9595. doi: 10.3390/ijerph18189595
Odeh, R., Diehl, E. R. M., Nixon, S. J., Tisher, C. C., Klempner, D., Sonke, J. K., et al. (2022). A pilot randomized controlled trial of group-based indoor gardening and art activities demonstrates therapeutic benefits to healthy women. PLoS ONE 17, e0269248. doi: 10.1371/journal.pone.0269248
Oh, Y-. A., Lee, A-. Y., An, K. J., and Park, S-. A. (2020). Horticultural therapy program for improving emotional wellbeing of elementary school students: an observational study. Integrative Med. Res. 9, 37–41. doi: 10.1016/j.imr.2020.01.007
Pálsdóttir, A. M., Grahn, P., and Persson, D. (2013). Changes in experienced value of everyday occupations after nature-based vocational rehabilitation. Scand. J. Occup. Ther., 1–11. doi: 10.3109/11038128.2013.832794
Park, S-. A., Lee, A-. Y., Lee, K-. S., and Son, K-. C. (2014). Gardening tasks performed by adults are moderate-to high-intensity physical activities. Horttechnology 24, 58–63. doi: 10.21273/HORTTECH.24.1.58
Park, S-. A., Lee, A-. Y., Park, H-. G., Son, K-. C., Kim, D-. S., Lee, W-. L., et al. (2017a). Gardening intervention as a low- to moderate-intensity physical activity for improving blood lipid profiles, blood pressure, inflammation, and oxidative stress in women over the age of 70: a pilot study. Horts 52, 200–205. doi: 10.21273/HORTSCI11232-16
Park, S-. A., Song, C., Oh, Y-. A., Miyazaki, Y., and Son, K-. C. (2017b). Comparison of physiological and psychological relaxation using measurements of heart rate variability, prefrontal cortex activity, and subjective indexes after completing tasks with and without foliage plants. IJERPH 14, 1087. doi: 10.3390/ijerph14091087
R Core Team. (2020). R: A Language and Environment for Statistical Computing. R Foundation for Statistical Computing, Vienna, Austria. Available online at: https://www.R-project.org/
Santomauro, D. F., Herrera, A. M. M., Shadid, J., Zheng, P., Ashbaugh, C., Pigott, D. M., et al. (2021). Global prevalence and burden of depressive and anxiety disorders in 204 countries and territories in 2020 due to the COVID-19 pandemic. Lancet 398, 1700–1712. doi: 10.1016/S0140-6736(21)02143-7
Sawaumi, T., Yamaguchi, S., Park, J., and Robinson, A. R. (2015). Japanese control strategies regulated by urgency and interpersonal harmony: evidence based on extended conceptual framework. J. Cross Cult. Psychol. 46, 252–268. doi: 10.1177/0022022114563749
Schneiderman, N., Ironson, G., and Siegel, S. D. (2005). Stress and health: psychological, behavioral, and biological determinants. Annu. Rev. Clin. Psychol. 1, 607–628. doi: 10.1146/annurev.clinpsy.1.102803.144141
Spano, G., D'Este, M., Giannico, V., Carrus, G., Elia, M., Lafortezza, R., et al. (2020). Are community gardening and horticultural interventions beneficial for psychosocial wellbeing? A meta-analysis. Int. J. Environ. Res. Public Health 17, 3584. doi: 10.3390/ijerph17103584
Szczepańska-Gieracha, J., Cieślik, B., Serweta, A., and Klajs, K. (2021). Virtual therapeutic garden: a promising method supporting the treatment of depressive symptoms in late-life: a randomized pilot study. JCM 10, 1942. doi: 10.3390/jcm10091942
Tao, J., Hassan, A., Qibing, C., Yinggao, L., Li, G., Jiang, M., et al. (2020). Psychological and physiological relaxation induced by nature-working with ornamental plants. Dis Dyn Nat Society 2020, 1–7. doi: 10.1155/2020/6784512
Tao, M., Lu, L., Gao, J., and He, X. (2022). Horticultural activities can achieve the same affect improvement effect of green exercise: a randomized field controlled trial. Front. Psychol. 13. doi: 10.3389/fpsyg.2022.989919
Tu, P-. C., Cheng, W-. C., Hou, P-. C., and Chang, Y-. S. (2020). Effects of types of horticultural activity on the physical and mental state of elderly individuals. IJERPH 17, 5225. doi: 10.3390/ijerph17145225
Ulrich, R. S., Cordoza, M., Gardiner, S. K., Manulik, B. J., Fitzpatrick, P. S., Hazen, T. M., et al. (2020). ICU patient family stress recovery during breaks in a hospital garden and indoor environments. HERD 13, 83–102. doi: 10.1177/1937586719867157
Ulrich, R. S., Simons, R. F., Losito, B. D., Fiorito, E., Miles, M. A., Zelson, M., et al. (1991). Stress recovery during exposure to natural and urban environments. J. Environ. Psychol. 11, 201–230. doi: 10.1016/S0272-4944(05)80184-7
Wang, Z., Zhang, Y., Lu, S., Tan, L., Guo, W., Lown, M., et al. (2022). Horticultural therapy for general health in the older adults: a systematic review and meta-analysis. PLoS ONE 17, e0263598. doi: 10.1371/journal.pone.0263598
Wei, M., Ku, T-. Y., and Liao, K. Y-. H. (2011). Minority stress and college persistence attitudes among African American, Asian American, and Latino students: perception of university environment as a mediator. Cult. Divers. Ethn. Minor. Psychol. 17, 195–203. doi: 10.1037/a0023359
Wei, Y., Dong, Z., Yu, W., Huang, Q., and Li, S. (2020). Study on the physical and psychological effect of the four different horticultural activitieson the elderly without family members. J. Northwestern Univ. Nat. Sci. Edn. 50, 11. doi: 10.16152/j.cnki.xdxbzr.2020-06-007
World Health Assembly (2012). Global Burden of Mental Disorders and The Need For a Comprehensive, Coordinated Response From Health And Social Sectors At The Country Level: Report by the Secretariat. Geneva: World Health Organization.
World Health Organization (2020). Doing what matters in times of stress: an illustrated guide. Geneva: World Health Organization Available at: https://apps.who.int/iris/handle/10665/331901.
Zhang, Y. W., Wang, J., and Fang, T. H. (2022). The effect of horticultural therapy on depressive symptoms among the elderly: a systematic review and meta-analysis. Front. Public Health 10. doi: 10.3389/fpubh.2022.953363
Keywords: horticultural activities, stress, environmental settings, theoretical framework, meta-analysis
Citation: Lu S, Liu J, Xu M and Xu F (2023) Horticultural therapy for stress reduction: A systematic review and meta-analysis. Front. Psychol. 14:1086121. doi: 10.3389/fpsyg.2023.1086121
Received: 23 November 2022; Accepted: 01 March 2023;
Published: 26 July 2023.
Edited by:Yuka Kotozaki, Iwate Medical University, Japan
Reviewed by:Esther Chow, City University of Hong Kong, Hong Kong SAR, China
Chongxian Chen, South China Agricultural University, China
Copyright © 2023 Lu, Liu, Xu and Xu. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Feng Xu, firstname.lastname@example.org