A new systematic review and meta-analysis provides evidence that Social and Therapeutic Horticulture may be an effective intervention for reducing symptoms of depression and anxiety. The findings suggest that structured gardening programs led by trained practitioners can offer mental health benefits compared to control conditions. The research was published in the journal Frontiers in Psychiatry.

Depression and anxiety are the two most prevalent mental health conditions globally. They often occur together and place a substantial burden on healthcare systems. While treatments such as antidepressant medications and psychological therapies exist, they are not effective for everyone. Many patients face challenges with medication adherence or do not achieve full recovery through talking therapies alone. Additionally, the demand for mental health support frequently exceeds the capacity of health services, leading to long waiting lists and delays in care.

Public health officials and medical professionals are increasingly interested in sustainable, community-based treatment options to address this gap. Nature-based interventions have gained attention for their potential to improve well-being. Social and Therapeutic Horticulture, or STH, is a specific type of nature-based intervention that involves the use of plants and gardening activities to improve physical and psychological health. Unlike casual gardening, this therapy is facilitated by trained practitioners who tailor activities to meet specific recovery goals.

The researchers aimed to synthesize existing evidence to determine the effectiveness of these horticultural interventions specifically for depression and anxiety. Previous reviews have often combined various types of gardening or focused on broad well-being outcomes rather than specific clinical symptoms. The new study sought to provide a rigorous analysis of quantitative data to inform future healthcare commissioning and policy.

“Our previous research exploring the barriers to commissioning social and therapeutic horticulture interventions in mental health care identified that the lack of evidence of its effectiveness for specific conditions (such as depression and anxiety) was a barrier to commissioning. This study was therefore undertaken to strengthen the evidence base and the justification for use of STH interventions in mental health care,” said study author Carly J. Wood, a senior lecturer at the University of Essex.

To conduct the study, the investigators followed the Preferred Reporting Items for Systematic Reviews and Meta-analysis guidelines. They performed a systematic search of multiple scientific databases and grey literature to identify relevant studies published in English. The search included terms related to horticulture, gardening, depression, and anxiety.

The review included studies that met strict eligibility criteria. Participants had to be adults aged eighteen or older who were identified as at risk for, or having symptoms of, depression or anxiety. The interventions were required to be led by trained practitioners and focus primarily on horticultural activities. Studies also needed to report on depression or anxiety outcomes using validated measurement scales.

The researchers identified seventeen unique studies that fit these criteria. These included four randomized controlled trials, ten quasi-experimental studies with comparison groups, and three single-group studies. The total sample consisted of 879 participants. The studies were conducted in several countries, with the majority taking place in Korea and others in the United States, China, Sweden, and Switzerland.

Participants in the included studies represented a diverse range of populations. Some studies focused on individuals with clinical diagnoses of mental health conditions, such as major depressive disorder or schizophrenia. Others involved participants with physical health conditions like stroke or chronic pain, or those in adverse social circumstances, including homeless individuals and elderly people in care facilities.

The interventions took place in various settings. Some were conducted entirely indoors, such as in hospitals or greenhouses, while others utilized outdoor community gardens or university campuses. The activities varied but generally included tasks like sowing seeds, potting plants, digging, weeding, and arranging flowers. The duration of the programs ranged from four weeks to sixteen weeks, with session lengths varying from thirty minutes to several hours.

The researchers extracted data from the eligible studies and performed a random effects meta-analysis to calculate the standardized mean difference. This statistical method allows for the comparison of results across studies that use different scales to measure the same outcome.

For depression, the meta-analysis included eleven studies with comparator groups. The results showed a large and significant effect in favor of the horticultural therapy group. This indicates that participants who engaged in the gardening interventions experienced a greater reduction in depressive symptoms than those in the control groups. When the researchers removed one outlier study involving stroke patients, the effect size remained moderate and significant.

For anxiety, the meta-analysis included six studies with comparator groups. The analysis revealed a moderate and significant effect in favor of the horticultural therapy group. Participants in the intervention groups reported greater reductions in anxiety symptoms compared to those who received standard care or other comparison activities.

The findings provide evidence that “STH interventions can be used to support a range of different treatment approaches for depression and anxiety, with combined global data indicating that these interventions are more effective at reducing symptoms of depression and anxiety that a variety of different comparators,” Wood told PsyPost.

The review also examined whether the setting of the intervention influenced the results. The analysis found no significant difference in effectiveness between interventions conducted indoors and those conducted outdoors or in mixed settings. This suggests that Social and Therapeutic Horticulture can be beneficial regardless of the physical environment, provided it is led by a trained practitioner.

The researchers also explored the impact of symptom severity at the start of the intervention. The beneficial effects were observed in participants with both mild and moderate-to-severe symptoms of depression and anxiety. This implies that horticultural therapy may be suitable for individuals at various stages of mental ill-health.

Despite the positive findings, the researchers noted some limitations in the existing evidence base. The overall quality of the included studies was low, with a high risk of bias. This was often due to the inability to blind participants to the intervention, as individuals know when they are participating in gardening activities. Many studies also lacked long-term follow-up data, making it difficult to determine if the benefits persist over time.

There was significant heterogeneity, or variability, in the results across the studies. This variation may be due to differences in the populations studied, the specific activities involved, and the cultural contexts in which the interventions took place. For instance, the high number of studies from Korea, where gardening has strong cultural roots, might influence the generalizability of the findings to other regions.

Another limitation is the nature of the comparison groups. In most studies, the control group received “treatment as usual” for a primary physical or social condition rather than a standard mental health treatment. Consequently, the review could not determine how Social and Therapeutic Horticulture compares directly to established treatments for depression and anxiety, such as cognitive behavioral therapy or medication.

“A common misconception is that STH is the same as all other types of gardening (e.g. gardening at home, on an allotment or community facility),” Wood noted. “”However, this is not the case. STH is a therapeutic intervention led by a trained practitioner to support individuals with ill-health, disability, or disadvantage in working towards set outcomes or objectives.”

The researchers conclude that Social and Therapeutic Horticulture has the potential to support existing treatment approaches for depression and anxiety. The interventions appear to be effective across a range of settings and for individuals with varying levels of symptom severity. The ability to address mental health needs alongside physical and social rehabilitation makes it a versatile option for diverse patient groups.

Future research should prioritize rigorous randomized controlled trials that compare horticultural therapy directly to standard mental health treatments. The authors suggest that such studies would help establish the cost-effectiveness of these interventions. They also recommend that future investigations explore the specific mechanisms that drive the observed health improvements.

“To continue to build the evidence base on the effectiveness of STH for mental health, we would like to undertake research to compare its effectiveness to other modes of treatment for depression and anxiety (e.g. talking therapies) and explore whom these interventions work best for and in what circumstances,” Wood said. “This will enable the benefits of STH interventions to be maximized.”

The study, “Effectiveness of social and therapeutic horticulture for reducing symptoms of depression and anxiety: a systematic review and meta-analysis,” was authored by Carly J. Wood, Jo Barton, and Claire L. Wicks.

A new systematic review and meta-analysis provides evidence that Social and Therapeutic Horticulture may be an effective intervention for reducing symptoms of depression and anxiety. The findings suggest that structured gardening programs led by trained practitioners can offer mental health benefits compared to control conditions. The research was published in the journal Frontiers in Psychiatry.

Depression and anxiety are the two most prevalent mental health conditions globally. They often occur together and place a substantial burden on healthcare systems. While treatments such as antidepressant medications and psychological therapies exist, they are not effective for everyone. Many patients face challenges with medication adherence or do not achieve full recovery through talking therapies alone. Additionally, the demand for mental health support frequently exceeds the capacity of health services, leading to long waiting lists and delays in care.

Public health officials and medical professionals are increasingly interested in sustainable, community-based treatment options to address this gap. Nature-based interventions have gained attention for their potential to improve well-being. Social and Therapeutic Horticulture, or STH, is a specific type of nature-based intervention that involves the use of plants and gardening activities to improve physical and psychological health. Unlike casual gardening, this therapy is facilitated by trained practitioners who tailor activities to meet specific recovery goals.

The researchers aimed to synthesize existing evidence to determine the effectiveness of these horticultural interventions specifically for depression and anxiety. Previous reviews have often combined various types of gardening or focused on broad well-being outcomes rather than specific clinical symptoms. The new study sought to provide a rigorous analysis of quantitative data to inform future healthcare commissioning and policy.

“Our previous research exploring the barriers to commissioning social and therapeutic horticulture interventions in mental health care identified that the lack of evidence of its effectiveness for specific conditions (such as depression and anxiety) was a barrier to commissioning. This study was therefore undertaken to strengthen the evidence base and the justification for use of STH interventions in mental health care,” said study author Carly J. Wood, a senior lecturer at the University of Essex.

To conduct the study, the investigators followed the Preferred Reporting Items for Systematic Reviews and Meta-analysis guidelines. They performed a systematic search of multiple scientific databases and grey literature to identify relevant studies published in English. The search included terms related to horticulture, gardening, depression, and anxiety.

The review included studies that met strict eligibility criteria. Participants had to be adults aged eighteen or older who were identified as at risk for, or having symptoms of, depression or anxiety. The interventions were required to be led by trained practitioners and focus primarily on horticultural activities. Studies also needed to report on depression or anxiety outcomes using validated measurement scales.

The researchers identified seventeen unique studies that fit these criteria. These included four randomized controlled trials, ten quasi-experimental studies with comparison groups, and three single-group studies. The total sample consisted of 879 participants. The studies were conducted in several countries, with the majority taking place in Korea and others in the United States, China, Sweden, and Switzerland.

Participants in the included studies represented a diverse range of populations. Some studies focused on individuals with clinical diagnoses of mental health conditions, such as major depressive disorder or schizophrenia. Others involved participants with physical health conditions like stroke or chronic pain, or those in adverse social circumstances, including homeless individuals and elderly people in care facilities.

The interventions took place in various settings. Some were conducted entirely indoors, such as in hospitals or greenhouses, while others utilized outdoor community gardens or university campuses. The activities varied but generally included tasks like sowing seeds, potting plants, digging, weeding, and arranging flowers. The duration of the programs ranged from four weeks to sixteen weeks, with session lengths varying from thirty minutes to several hours.

The researchers extracted data from the eligible studies and performed a random effects meta-analysis to calculate the standardized mean difference. This statistical method allows for the comparison of results across studies that use different scales to measure the same outcome.

For depression, the meta-analysis included eleven studies with comparator groups. The results showed a large and significant effect in favor of the horticultural therapy group. This indicates that participants who engaged in the gardening interventions experienced a greater reduction in depressive symptoms than those in the control groups. When the researchers removed one outlier study involving stroke patients, the effect size remained moderate and significant.

For anxiety, the meta-analysis included six studies with comparator groups. The analysis revealed a moderate and significant effect in favor of the horticultural therapy group. Participants in the intervention groups reported greater reductions in anxiety symptoms compared to those who received standard care or other comparison activities.

The findings provide evidence that “STH interventions can be used to support a range of different treatment approaches for depression and anxiety, with combined global data indicating that these interventions are more effective at reducing symptoms of depression and anxiety that a variety of different comparators,” Wood told PsyPost.

The review also examined whether the setting of the intervention influenced the results. The analysis found no significant difference in effectiveness between interventions conducted indoors and those conducted outdoors or in mixed settings. This suggests that Social and Therapeutic Horticulture can be beneficial regardless of the physical environment, provided it is led by a trained practitioner.

The researchers also explored the impact of symptom severity at the start of the intervention. The beneficial effects were observed in participants with both mild and moderate-to-severe symptoms of depression and anxiety. This implies that horticultural therapy may be suitable for individuals at various stages of mental ill-health.

Despite the positive findings, the researchers noted some limitations in the existing evidence base. The overall quality of the included studies was low, with a high risk of bias. This was often due to the inability to blind participants to the intervention, as individuals know when they are participating in gardening activities. Many studies also lacked long-term follow-up data, making it difficult to determine if the benefits persist over time.

There was significant heterogeneity, or variability, in the results across the studies. This variation may be due to differences in the populations studied, the specific activities involved, and the cultural contexts in which the interventions took place. For instance, the high number of studies from Korea, where gardening has strong cultural roots, might influence the generalizability of the findings to other regions.

Another limitation is the nature of the comparison groups. In most studies, the control group received “treatment as usual” for a primary physical or social condition rather than a standard mental health treatment. Consequently, the review could not determine how Social and Therapeutic Horticulture compares directly to established treatments for depression and anxiety, such as cognitive behavioral therapy or medication.

“A common misconception is that STH is the same as all other types of gardening (e.g. gardening at home, on an allotment or community facility),” Wood noted. “”However, this is not the case. STH is a therapeutic intervention led by a trained practitioner to support individuals with ill-health, disability, or disadvantage in working towards set outcomes or objectives.”

The researchers conclude that Social and Therapeutic Horticulture has the potential to support existing treatment approaches for depression and anxiety. The interventions appear to be effective across a range of settings and for individuals with varying levels of symptom severity. The ability to address mental health needs alongside physical and social rehabilitation makes it a versatile option for diverse patient groups.

Future research should prioritize rigorous randomized controlled trials that compare horticultural therapy directly to standard mental health treatments. The authors suggest that such studies would help establish the cost-effectiveness of these interventions. They also recommend that future investigations explore the specific mechanisms that drive the observed health improvements.

“To continue to build the evidence base on the effectiveness of STH for mental health, we would like to undertake research to compare its effectiveness to other modes of treatment for depression and anxiety (e.g. talking therapies) and explore whom these interventions work best for and in what circumstances,” Wood said. “This will enable the benefits of STH interventions to be maximized.”

The study, “Effectiveness of social and therapeutic horticulture for reducing symptoms of depression and anxiety: a systematic review and meta-analysis,” was authored by Carly J. Wood, Jo Barton, and Claire L. Wicks.