The Impact of Nature Exposure on Mental Health and Cognitive Performance: A Systematic Review of Mechanisms, Meta-Analytic Evidence, and Clinical Applications

Abstract

Nature exposure has been proposed as a low-cost, scalable intervention for improving mental health and cognitive function, yet the magnitude and specificity of its benefits remain debated. This systematic literature review synthesizes research published between 2012 and 2025 from PsycINFO, PubMed, Scopus, and Web of Science to examine how different forms of nature contact, such as green space access, forest therapy, nature-based interventions, and passive nature viewing, affect psychological well-being and cognitive performance. The review integrates two principal theoretical frameworks: Attention Restoration Theory (ART), which posits that natural environments replenish directed attention through involuntary "soft fascination," and Stress Reduction Theory (SRT), which emphasizes the psychophysiological calming effects of nature via the parasympathetic nervous system. Meta-analytic evidence indicates that nature exposure reliably improves mood and reduces negative affect, with forest therapy showing moderate-to-large effects on stress (SMD = –0.71), depressive symptoms (SMD = –0.68), and anxiety (SMD = –0.77) in clinical populations. However, evidence for cognitive benefits is weaker and more domain-specific: working memory and attentional control show reliable improvements, but effects are small (mean SMD ≈ 0.20 to 0.30) and highly heterogeneous. A meta-analysis of 80 studies (273 outcomes) found that nature is more restorative than non-nature exposure for overall cognitive capacity, with benefits largest after approximately 30 minutes of exposure. Green space access is associated with reduced odds of depression (OR = 0.71) and anxiety (OR = 0.73) during population-level crises, and residential greenness is associated with a 15% lower risk of neurodegenerative diseases (pooled HR = 0.85), though evidence quality is very low due to high heterogeneity and bias. Neurobiologically, nature exposure in children and youth is associated with increased prefrontal cortex gray matter volume, decreased sympathetic activity, increased parasympathetic activity, and, when combined with cognitive task engagement, enhanced attentional processing reflected in increased brain activity. Moderators include exposure duration (30-minute optimum), cognitive fatigue state (larger benefits for fatigued individuals), age (children and adolescents benefit equally), and intervention type (multisession forest therapy outperforms single exposures). Significant gaps persist regarding long-term durability of effects, the translation of experimental findings into real-world urban planning, the distinction between active (hiking, gardening) and passive (viewing, walking) nature contact, and the development of standardized, dose-response guidelines. The review concludes by proposing a research agenda focused on large-scale, long-term randomized controlled trials of nature-based interventions in clinical populations; the integration of multimodal outcome assessment (self-report, physiological, neuroimaging, behavioral); the identification of active therapeutic ingredients and mechanistic pathways; and the translation of evidence into actionable public health and urban design policies for dementia prevention and mental health promotion.