Hannah Roberts1, Caspar van Lissa2, Paulien Hagedoorn3, Ian Kellar4, Marco Helbich3. 1. Department of Human Geography and Spatial Planning, Utrecht University, Netherlands. Electronic address: h.e.roberts@uu.nl. 2. Department of Methodology and Statistics, Utrecht University, Netherlands. 3. Department of Human Geography and Spatial Planning, Utrecht University, Netherlands. 4. School of Psychology, University of Leeds, United Kingdom.
Abstract
BACKGROUND: Research suggests that exposure to the natural environment can improve mood, however, current reviews are limited in scope and there is little understanding of moderators. OBJECTIVE: To conduct a comprehensive systematic review and meta-analysis of the evidence for the effect of short-term exposure to the natural environment on depressive mood. METHODS: Five databases were systematically searched for relevant studies published up to March 2018. Risk of bias was evaluated using the Cochrane Risk of Bias (ROB) tool 1.0 and the Risk of Bias in Non-Randomised Studies of Interventions (ROBINS-I) tool where appropriate. The Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) approach was used to assess the quality of evidence overall. A random-effects meta-analysis was performed. 20 potential moderators of the effect size were coded and the machine learning-based MetaForest algorithm was used to identify relevant moderators. These were then entered into a meta-regression. RESULTS: 33 studies met the inclusion criteria. Effect sizes ranged from -2.30 to 0.84, with an unweighted mean effect size of Mg=-0.29,SD=0.60. However, there was significant residual heterogeneity between studies and risk of bias was high. Type of natural environment, type of built environment, gender mix of the sample, and region of study origin, among others, were identified as relevant moderators but were not significant when entered in a meta-regression. The quality of evidence was rated very low to low. An assessment of publication bias was inconclusive. CONCLUSIONS: A small effect was found for reduction in depressive mood following exposure to the natural environment. However, the high risk of bias and low quality of studies limits confidence in the results. The variation in effect size also remains largely unexplained. It is recommended that future studies make use of reporting guidelines and aim to reduce the potential for bias where possible.
BACKGROUND: Research suggests that exposure to the natural environment can improve mood, however, current reviews are limited in scope and there is little understanding of moderators. OBJECTIVE: To conduct a comprehensive systematic review and meta-analysis of the evidence for the effect of short-term exposure to the natural environment on depressive mood. METHODS: Five databases were systematically searched for relevant studies published up to March 2018. Risk of bias was evaluated using the Cochrane Risk of Bias (ROB) tool 1.0 and the Risk of Bias in Non-Randomised Studies of Interventions (ROBINS-I) tool where appropriate. The Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) approach was used to assess the quality of evidence overall. A random-effects meta-analysis was performed. 20 potential moderators of the effect size were coded and the machine learning-based MetaForest algorithm was used to identify relevant moderators. These were then entered into a meta-regression. RESULTS: 33 studies met the inclusion criteria. Effect sizes ranged from -2.30 to 0.84, with an unweighted mean effect size of Mg=-0.29,SD=0.60. However, there was significant residual heterogeneity between studies and risk of bias was high. Type of natural environment, type of built environment, gender mix of the sample, and region of study origin, among others, were identified as relevant moderators but were not significant when entered in a meta-regression. The quality of evidence was rated very low to low. An assessment of publication bias was inconclusive. CONCLUSIONS: A small effect was found for reduction in depressive mood following exposure to the natural environment. However, the high risk of bias and low quality of studies limits confidence in the results. The variation in effect size also remains largely unexplained. It is recommended that future studies make use of reporting guidelines and aim to reduce the potential for bias where possible.
Authors: Hector A Olvera-Alvarez; Matthew H E M Browning; Andreas M Neophytou; Gregory N Bratman Journal: Int J Environ Res Public Health Date: 2021-01-10 Impact factor: 3.390
Authors: Elise Peters; Jolanda Maas; Dieuwke Hovinga; Nicole Van den Bogerd; Carlo Schuengel Journal: Int J Environ Res Public Health Date: 2020-11-21 Impact factor: 3.390
Authors: Giuseppe Riva; Luca Bernardelli; Matthew H E M Browning; Gianluca Castelnuovo; Silvia Cavedoni; Alice Chirico; Pietro Cipresso; Dirce Maria Bengel de Paula; Daniele Di Lernia; Javier Fernández-Álvarez; Natàlia Figueras-Puigderrajols; Kei Fuji; Andrea Gaggioli; Jose Gutiérrez-Maldonado; Upyong Hong; Valentina Mancuso; Milena Mazzeo; Enrico Molinari; Luciana F Moretti; Angelica B Ortiz de Gortari; Francesco Pagnini; Elisa Pedroli; Claudia Repetto; Francesca Sforza; Chiara Stramba-Badiale; Cosimo Tuena; Clelia Malighetti; Daniela Villani; Brenda K Wiederhold Journal: Front Psychiatry Date: 2020-09-23 Impact factor: 4.157