(NEWS) Nature-based interventions & mental health: Umbrella review shows moderate evidence

A walk in the woods, time spent in the garden, or a visit to the park—can such nature-based interventions truly boost mental health? A new umbrella review published in JAMA Psychiatry (March 2026) examined 28 systematic reviews with meta-analyses of a total of 344 studies. The results: moderate evidence for a reduction in tension (SMD -0.87), fatigue (SMD -0.80), and negative affect (SMD -0.51), plus an increase in positive affect (SMD 0.98) and well-being (SMD 0.40). However, 89% of the associations have low to very low quality evidence. How exactly do nature-based interventions work? For whom are they best suited? This article explains the latest findings—practical and evidence-based.

What the Umbrella Review shows

To clarify whether and how nature influences our psyche, researchers have compiled all available data in a large-scale "umbrella review." An umbrella review is the highest level of evidence in science, as it combines not just individual studies, but all existing meta-analyses on a topic – essentially a "best of" the research.

• Study type: Umbrella Review & Meta-Analysis (comprehensive synthesis of 28 systematic reviews).

• Data basis: A total of 344 original studies in which 91 different associations between nature and psyche were analyzed.

• Publication: JAMA Psychiatry (Tier-1 Journal), March 4, 2026.

• Tension: SMD -0.87 (95% CI -1.31; -0.43). This means that nature-based interventions reduced feelings of tension by 87% of one standard deviation – a large effect.

• Fatigue: SMD -0.80 (95% CI -1.16; -0.44). Subjective exhaustion decreased significantly.

• Confusion: SMD -0.65 (95% CI -1.12; -0.19). Cognitive clarity improved.

• Negative affect: SMD -0.51 (95% CI -0.85; -0.16). Negative feelings and moods were moderately reduced.

• Positive affect: SMD 0.98 (95% CI 0.65; 1.30). Almost a full standard deviation improvement – a very strong effect on good mood and optimism!

• Vitality (Vigor): SMD 0.83 (95% CI 0.37; 1.28). The feeling of energy and liveliness increased significantly.

• Well-being: SMD 0.40 (95% CI 0.07; 0.73). A small to moderate effect on general well-being.

• Quality of evidence: Important for context: Only 10 of the 91 associations examined (11%) showed moderate quality of evidence. The vast majority (89%) had low to very low quality.

• Climate factor: Interventions that specifically address psychological stress caused by climate change (e.g., heat anxiety) currently have a very low evidence base.

Mechanism: How do nature-based interventions work?

Why do we often feel calmer in the forest than in the city? Science has identified several physiological and psychological explanations for this that go far beyond mere "imagination".

• Stress reduction through parasympathetic activation: Natural environments signal safety to our brain. This activates the parasympathetic nervous system (the "rest and digest" mode). As a result, heart rate and blood pressure decrease, and cortisol levels in the blood are reduced.

• Attention Restoration Theory: Modern daily life demands constant, focused attention (screens, traffic). Nature offers "soft fascination" that requires no effort. This allows our cognitive resources to regenerate – we recover from mental exhaustion.

• Biophilia hypothesis: Humans have evolved in nature over millennia. We possess an evolutionary, innate connection to natural environments. Spending time in nature therefore activates reward systems in the brain, giving us a feeling of "home" and security.

• Social interaction: Nature-based activities such as gardening in community gardens or walks in parks often promote social contact. This reduces loneliness, a major driver of mental health problems.

• Physical activity: Many nature-based interventions include gentle exercise (hiking, gardening). Exercise alone already leads to the release of endorphins and neurotransmitters such as serotonin.

• Sensory stimuli: Natural sounds (birdsong, rustling leaves), organic scents (forest floor, flowers) and visually appealing green hues (fractals in plants) have a direct calming effect on the central nervous system.

Dosage & Application

How much nature do you need to benefit from the effects? The good news is: you don't have to spend weeks in the wilderness. Research shows that even small doses are effective.

• Optimal duration: Even 20-30 minutes spent in nature shows measurable physiological effects (e.g., cortisol reduction).

• Ideal weekly dose: Studies suggest that around 120 minutes per week is ideal. It doesn't matter whether you spend these 2 hours in one go or spread them out over several shorter sessions.

• Timing: Contact with nature is valuable at any time. However, spending time in nature in the morning or forenoon is often particularly effective, as natural daylight also regulates your circadian rhythm (sleep-wake cycle).

• Type of nature: It doesn't have to be a primeval forest. Forests, urban parks, private gardens, beaches or riverbanks – almost all forms of natural environments have positive effects.

• Indoor vs. Outdoor: Real "outdoor" nature is significantly more effective. While houseplants or nature pictures may have some positive effects, they cannot replace the experience of being outdoors with all your senses (wind, temperature, smell).

• Activity: You don't have to do any sport. Both passive exposure to nature (sitting on a park bench, observing) and active activities (hiking, gardening) are effective.

• Combination: The combination with mindfulness exercises, such as the Japanese "Shinrin Yoku" (forest bathing), which focuses on consciously perceiving the surroundings, is particularly effective.

• Consistency: As with sports or nutrition, regular exposure is more important and sustainable than a single long stay. Make nature a routine.

For whom is nature-based intervention particularly suitable?

The results of the Umbrella Review suggest that almost everyone benefits from spending more time outdoors. However, there are groups for whom this intervention is particularly promising.

• For people with stress, anxiety & mild depression: The moderate evidence for the reduction of tension and negative affect makes spending time in nature an excellent complementary measure for symptom relief.

• Adults of all age groups: The positive effects on the psyche are largely independent of age, from young adults to senior citizens.

• City dwellers: For people in urban areas with high noise and stimulus density, consciously finding balance in green spaces is particularly important ("Urban Stress Recovery").

• Preventive health: You don't have to be sick to benefit. Even for people without a diagnosis, nature is an important tool for promoting resilience and increasing overall well-being.

• Complementary to therapy: Nature-based interventions can meaningfully complement psychological treatments. They serve as an easily accessible, free resource in everyday life, but do not replace therapy.

• Responder rate: Although exact percentages are not available, individual differences are likely. Some people respond more strongly to natural stimuli than others – try out what works for you.

Limitations of the Umbrella Review

1. Low quality of evidence: A major criticism from the authors is that 89% of all associations examined had only low to very low quality of evidence. This is often due to methodological weaknesses in the original studies (e.g., lack of blinding, small groups) or publication bias.

2. Heterogeneity of interventions: The term "nature-based interventions" is extremely broad. It encompasses everything from forest bathing and gardening to pure nature therapy or visits to parks. This makes it difficult to derive a single, specific recommendation for action that applies to everyone.

3. Lack of climate change-specific evidence: There is a significant research gap regarding interventions that specifically address the psychological consequences of climate change (e.g., fear of extreme weather or heat). The evidence in this area is currently very limited.

4. Short-term effects dominate: Most studies included in the analysis only measure the immediate effects (hours to a few weeks). Whether and for how long the positive effects persist after the intervention ends is not yet sufficiently clear scientifically.

5. Uncertainty about the dose-response relationship: Although we have guidelines, the absolutely precise "dose" (optimal duration, frequency, and exact nature of the treatment) is not yet clearly defined scientifically. Long-term studies on the optimal "prescription" of natural remedies are lacking.

⚠ Important note:

This information is for general informational purposes only and does not constitute medical advice. Nature-based interventions can complement psychological treatment, but do not replace it. Professional psychotherapeutic or psychiatric treatment is essential for severe depressive symptoms, suicidal thoughts, or anxiety disorders. Always consult qualified professionals for any health problems.

Sources

1. Rodriguez-Rivas ME, Warnell KJD, Moore AD, et al. (2026). Climate-Related and Nature-Based Interventions for Mental Health: An Umbrella Review and Meta-Analysis. JAMA Psychiatry ; e260037. DOI: 10.1001/jamapsychiatry.2026.0037

2. Jessen NH, Ussing AM, Christensen J, et al. (2025). Effect of nature-based health interventions for individuals diagnosed with anxiety, depression and/or experiencing stress—a systematic review and meta-analysis. BMJ Open ; 15(7):e098598. DOI: 10.1136/bmjopen-2024-098598

3. Pouso S, Borja Á, Fleming LE, et al. (2021). Contact with blue-green spaces during the COVID-19 pandemic lockdown beneficial for mental health. Science of The Total Environment ; 756:143984. DOI: 10.1016/j.scitotenv.2020.143984