Natural environments and adolescent depression: A literature review

Abstract

With the acceleration of global urbanization, humanity’s disconnection from natural ecosystems has deepened, leading to a concurrent rise in adolescent “nature deficit disorder” and depression risk. In this context, explorations of the impact of natural environments on adolescent depression and the potential of such environments as sites of intervention have provided critical breakthroughs for alleviating the global adolescent mental health crisis. This study employs a literature review methodology to comprehensively synthesize empirical research and theoretical findings on the relationship between the natural environment and adolescent depression. It identifies the core, mediating, and moderating factors that influence this relationship while elucidating its theoretical foundations. On this basis, the study proposes improvement strategies and future research directions. By integrating existing findings, this study not only clarifies the core patterns linking the natural environment and adolescent depression but also provides a clear framework for the subsequent exploration of mechanisms and intervention practices. It aims to promote the standardized application of natural environments within adolescent mental health protection systems, thereby contributing to the sustainable improvement of global adolescent mental health levels.

Key Words: Natural environments; Nature-based interventions; Adolescents; Depression; Mechanisms

Core Tip: Nature-based interventions, in the context of global urbanization, are a new approach for preventing and alleviating adolescent depression. However, there are, notably, both opportunities and challenges in obtaining a systematic understanding of their mechanisms and applying them effectively. To mobilize the full potential of the natural environment and truly empower adolescent mental health, it is necessary to obtain a clear understanding of the core influencing factors and to comprehensively explore the standardized integration of nature into mental health protection systems.

INTRODUCTION

Depression poses a significant challenge to global public health, affecting approximately 20% of adolescents with depression and related mental health issues[1]. Since the 17^th century, depression has been defined as a state characterized by emotional despondency and pessimism, fundamentally involving an individual’s loss of capacity to experience happiness. As a common mental disorder, depression frequently cooccurs with emotional issues such as anxiety, fear, and loneliness, making it one of the primary risk factors threatening adolescents’ physical and mental health[2,3]. Adolescence represents a critical stage of rapid development across physiological, psychological, and social dimensions, during which individuals become more sensitive to external environmental changes, thereby increasing their vulnerability to mental health issues[4]. A 2021 joint report by United Nations International Children’s Emergency Fund and the World Health Organization indicated that globally, one in seven adolescents aged 10-19 years struggles with mental health issues[5]. Concurrently, modern societal stressors, including intense academic pressure, excessive social media use, and unstable family environments, increase the risk of depression among adolescents[6,7]. Depression not only negatively impacts adolescents’ physical health, psychological well-being, cognitive function, and social interactions but also, if not addressed promptly and effectively, may progress to major depressive disorder, imposing significant economic and social burdens on individuals, families, and society[8,9]. Given that many forms of environmental exposure during childhood exert profound, lasting effects into adulthood, in-depth exploration of the factors influencing adolescent depression and effective intervention pathways is critically needed and requires urgent attention in the field of public health.

As the foundation for human survival and development, the role of the natural environment in promoting physical and mental health is gaining increasing academic attention. However, accelerated urbanization and intensified human activities have structurally transformed our living environment, resulting in physical disconnection from natural ecosystems and weakened emotional bonds with nature. This trend has been confirmed to pose a potential threat to public mental health, particularly affecting adolescents during their critical developmental period[10]. In this review, to ensure conceptual clarity and practical relevance, we adopt a broad and inclusive definition of the “natural environment”. We acknowledge that for modern adolescents, the majority of whom reside in urbanized areas, daily access to pristine wilderness is limited. Therefore, the “natural environment” in this study encompasses not only remote natural ecosystems (e.g., forests and mountains) but also “urban nature” or “green/blue spaces”. These include city parks, community gardens, campus greenery, street trees, and accessible water bodies. While these settings may be human designed or managed, they represent the primary interface through which adolescents experience nature and derive psychological benefits. In recent years, substantial research has indicated that exposure to natural environments is closely linked to individuals’ psychological development trajectories. Against this backdrop, “nature connectedness” has emerged as a core concept attracting widespread interdisciplinary attention. Nature connectedness refers to the deep emotional and cognitive bonds that individuals form with nature, reflecting the dynamic relationship between humans and the natural world. Notably, amid the global rise in mental illness incidence, the scarcity of natural exposure during urbanization is viewed as a key contributing factor. Louv[11] introduced the concept of “nature-deficit disorder”, a nonclinical term describing the human costs of alienation from nature rather than a medical diagnosis, to address the “indoor-centric” lifestyle and disconnection from nature that have emerged with modernization. Indeed, recent data from the National Bureau of Statistics of China reveal a dramatic shift: In 2024, the average daily internet usage time for residents increased by 2 hours and 55 minutes compared with that in 2018, more than doubling in duration. Given that adolescents are a primary demographic for heavy internet use, this trend is likely even more pronounced among young people, significantly encroaching upon time previously available for outdoor nature engagement[12]. He argued that contemporary urban children, deprived of direct experiences of free exploration in natural spaces such as forests and fields, may develop a range of mental health issues. Research confirms that maintaining high levels of nature connection significantly buffers against negative emotions such as anxiety and depression while effectively enhancing subjective well-being and life satisfaction. These findings provide crucial theoretical grounding for understanding the protective effects of natural environments on mental health.

Given the profound impact of the natural environment on mental health and the severity of adolescent depression, systematically examining this relationship holds significant theoretical and practical importance. Research indicates that subjectively perceived nature connection is strongly associated with physical and mental health and plays a key mediating role between nature exposure and subjective well-being. This provides crucial insights into the underlying pathways through which the natural environment influences psychological states[13]. Despite substantial evidence supporting the health benefits of natural exposure, narrative reviews targeting adolescents remain limited. As a low-cost, highly accessible public resource, the natural environment offers unique potential for adolescent depression interventions. Nature exposure helps reduce rumination, regulate stress responses, and promote social interaction, thereby alleviating loneliness and other depression-related emotions[14]. This study aims to address the following core questions. Through which core factors, mediating mechanisms, and moderating variables does the natural environment influence adolescent depression? How can nature-based prevention and intervention strategies for adolescent depression be developed on the basis of existing research? What are the limitations of the current research? How should future research deepen and expand these findings?

METHODOLOGY

Search strategy and data sources

To provide a comprehensive overview of the relationship between the natural environment and adolescent depression, we conducted a narrative literature review. We identified relevant literature by searching authoritative multidisciplinary databases, including Web of Science, PubMed, PsycINFO, Scopus, and the Ei Compendex. The search covered articles published from the inception of the databases up to August 2025. The search strategy utilized combinations of core keywords across three domains: (1) “adolescents”, “youth”, “teenagers”, and “students”; (2) “natural environment”, “green space”, “blue space”, “urban parks”, and “nature exposure”; and (3) “depression”, “depressive symptoms”, “mental health”, and “emotional well-being”.

Inclusion and exclusion criteria

Studies were included on the basis of the following criteria: (1) Participants. Mainly adolescents and young adults (aged 10-24 years); (2) Topic. Examined the association between natural exposure and depression or related internalizing problems; (3) Study type. Empirical research published in peer-reviewed journals (including quantitative, qualitative, and mixed-method studies); and (4) Language. Published in English. We excluded nonempirical articles (e.g., editorials, commentaries); studies focusing solely on adults or young children; and studies where nature exposure was not a primary variable.

Study selection and synthesis

We employed a three-stage selection process to ensure relevance and quality as follows: (1) Initial screening. Titles and abstracts were screened to exclude clearly irrelevant studies; (2) Full-text rescreening. Full texts of potentially eligible articles were retrieved and reviewed against the inclusion criteria; and (3) Final confirmation. Selected studies were synthesized to identify key themes, mechanisms, and research gaps. This narrative synthesis approach allowed us to integrate diverse findings into the conceptual framework presented in the subsequent sections.

THE THEORETICAL BASIS FOR THE INFLUENCE OF NATURAL ENVIRONMENTS ON ADOLESCENT DEPRESSION

Psychological evolution theory

Psychological evolution theory, also known as stress recovery theory, provides a comprehensive explanation for the stress-reducing effects of natural environments from an interdisciplinary perspective that combines physiology and evolutionary biology. Ulrich et al[15] experimentally demonstrated that, compared with urban settings, human exposure to natural environments elicits more pronounced physiological relaxation responses, such as a slowed heart rate and reduced skin conductance, which are characterized by automaticity and immediacy[16]. Subsequently, Ulrich[17] refined this theory, proposing a core insight: Throughout human evolution, natural environments have consistently provided primary survival resources, food, water, safe shelter, and other essential elements. This long-term adaptation has imprinted an innate positive feedback mechanism in the human brain toward “nonthreatening natural settings”. When individuals are immersed in natural environments, such as forests, rivers, or green spaces, intrinsic stress-reduction processes are spontaneously activated. This occurs independently of conscious cognitive effort, representing an evolutionary “preset self-regulatory mechanism”. This theory holds particular explanatory power for adolescent populations. Adolescence is a period characterized by significant psychological stressors, including academic pressure and social anxiety. With their neuroendocrine systems still developing, adolescents possess weaker stress regulation capabilities than adults do[18]. At this stage, the “automatic stress reduction” properties of natural environments can rapidly alleviate physiological stress states. Brief stays in campus green spaces, for example, significantly lower adolescents’ cortisol levels, thereby preventing the accumulation of chronic stress that may trigger depressive symptoms[19].

Attention restoration theory

Kaplan’s attention restoration theory (ART), proposed in cognitive psychology, reveals the cognitive pathway through which natural environments alleviate adolescent depression from an “attention resource management” perspective[20]. The theory’s core premise distinguishes human attention systems into “voluntary attention” and “involuntary attention”[21]. The former requires individuals to actively expend volitional resources to filter distractions and focus on targets, leading to “cognitive fatigue” with prolonged use; the latter, however, operates without volitional involvement, is automatically triggered by stimuli possessing “intrinsic appeal” in the environment, such as swaying leaves or birdsong, and can restore attentional resources during engagement[22,23]. Research has indicated that natural environments possess four key qualities that promote attentional recovery. First, “charm”, dynamic elements such as streams and clouds, automatically captures attention without inducing a cognitive load. Second, “distance”, the way in which natural settings help individuals detach from stressors, creates psychological “temporary disengagement”. Third, “scope”, the expansive space and rich ecology of nature, satisfies psychological needs for a “sense of wholeness” and “desire to explore”, thereby preventing oppression stemming from cognitive constraints. Fourth, “compatibility” refers to how the rhythms of natural environments align closely with the innate cognitive rhythms of humans. Individuals can freely adjust behaviors and activities, such as walking or sitting quietly, on the basis of their state without passively adapting to environmental pressures[24]. Sustained demands on “attentional focus” from academic tasks make adolescents highly susceptible to cognitive fatigue, which further exacerbates their emotional sensitivity and depressive tendencies. Here, nature’s “attention restoration” function offers an effective intervention: Studies have reported that activities such as park cycling or countryside hiking significantly increase adolescents’ sustained attention capacity, reduce emotional exhaustion caused by cognitive fatigue, and consequently lower the incidence of depression symptoms[25]. In contrast, stimuli in urban environments, such as advertisements and traffic, may provide brief excitement but often constitute “high-intensity distractions”. Such stimuli require individuals to expend additional attentional resources for filtering and fail to achieve genuine cognitive restoration[26].

Biophilia hypothesis

Wilson’s “biophilia hypothesis” explains the profound nurturing effect of the natural environment on adolescent mental health, which is rooted in both emotional and evolutionary aspects. The core tenet of this theory is that over millions of years of evolution, humans have developed an innate “biophilia”, an instinctive need for closeness and connection with other life forms. This need is an evolutionary legacy essential for the survival and reproduction of human species. When individuals have ample access to nature and interact with other life forms, they experience a connection to their “evolutionary roots”, thereby gaining emotional security and a sense of existential meaning, ultimately promoting physical and mental well-being. Conversely, prolonged disconnection from nature, a form of “biological deprivation”, leads to emotional emptiness and psychological imbalance, becoming a potential precursor to mental health issues such as depression. The principles of ecological psychology further reinforce the explanatory power of the biophilia hypothesis. Reed emphasizes that natural environments are not mere “external backdrops” but vital conduits through which individuals can perceive their self-worth and the meaning of life. When adolescents care for plants, observe animal behaviors, or engage in natural exploration, they intuitively experience “life growth and resilience”. Such experiences foster positive self-perception, reducing the “self-denial” and “sense of meaninglessness” common in depressive states. Bennett further elaborates on the perspective of “otherness” whereby the natural environment comprises species, elements, and ecological processes that extend beyond humanity. This “nonanthropocentric” perspective helps adolescents transcend the confines of self-anxiety, view life challenges from a broader perspective, and alleviate the “cognitive narrowness” caused by depressive states. For contemporary adolescents, “nature deficit disorder” has become widespread, urbanization traps them in “concrete jungles”, replacing direct contact with nature with screens and indoor activities. The prolife hypothesis suggests that this “disconnection from nature” directly weakens adolescents’ emotional support systems. Conversely, regular interaction with nature fulfills their “pro-life needs”, enhancing subjective well-being through emotional bonds with the natural world and thereby forming an “emotional buffer zone” against depression.

CORE FACTORS THROUGH WHICH NATURAL ENVIRONMENTS INFLUENCE ADOLESCENT DEPRESSION

Positive factors

Green space: Because the natural environment is the context that is most closely tied to human daily activities, the protective effect of green space on adolescent depression has become a focal point in the interdisciplinary field of public health and environmental psychology. Its quantification typically involves metrics such as green coverage rate, vegetation type, and spatial accessibility. Research suggests that green space has a positive effect on mental health through three primary functions: Reducing environmental hazards, restoring individual capacity, and building social capital[27]. At the macro level, extensive empirical research has demonstrated a significant positive correlation between natural exposure, centered on residential green spaces, and adolescents’ psychological resilience and stress reduction[28,29]. This effect is not transient but rather exhibits long-term, life-course-spanning persistence. For example, data analysis from the Dutch PIAMA (Prevention and Incidence of Asthma and Mite Allergy) birth cohort (longitudinal; n = 3059; age 11-20 years) revealed that individuals with greater exposure to green space during childhood and adolescence presented a lower risk of poor mental well-being in early adulthood (odds ratio = 0.78, 95% confidence interval: 0.68-0.88)[30,31].

The pathways through which green spaces influence adolescent depression are multidimensional and intertwined. Physiologically, green spaces effectively reduce individuals’ physiological stress load by absorbing pollutants, lowering noise levels, and mitigating the urban heat island effect[32,33]. On the basis of ART, exposure to natural environments helps restore depleted directed attention, thereby enhancing emotional regulation. This manifests as significantly reduced fatigue, anger, and perceived stress among adolescents[27]. Socially, green spaces provide ideal venues for physical exercise and group interaction, strengthening adolescents’ social support networks and community cohesion, which in turn buffers high-risk factors for depression, such as loneliness. Notably, the protective effects of green spaces are not uniform, with specific characteristics playing a crucial role in these effects. Compared with other vegetation types, woodlands are more beneficial for adolescent mental health[34,35]. Moreover, the quality of green spaces (e.g., maintenance levels, safety) is more important than mere quantity, particularly for older adolescents, whose mental health is more closely linked to the quality of green spaces[36]. Moreover, the homogeneity of neighborhood green spaces is crucial; overly varied green space distributions may conversely be associated with reduced well-being[37]. The ecological attributes of green spaces are also significant factors. Research indicates that environmental quality, measured by validated metrics such as tree-species richness (e.g., Shannon diversity index) and vegetation density (e.g., normalized difference vegetation index), is critical. For instance, higher bird abundance within communities is correlated with lower levels of depression.

Blue space: As a vital component of the natural environment, blue space encompasses a diverse range of water bodies, including canals, ponds, lakes, and oceans. Its positive impact on adolescent mental health is emerging as a new research focus[38]. Like green space, blue space has significant potential for alleviating depressive symptoms and enhancing emotional well-being among adolescents because of its unique environmental attributes[39]. Its mechanisms of action are multidimensional, primarily stemming from distinctive patterns of sensory stimulation. The rhythmic undulation of waves, the murmuring sound of flowing water, and the dynamic play of light and shadow reflected on the water surface activate the “soft fascination” mechanism of the brain, a process closely linked to ART. Soft fascination gently redirects adolescents’ attention away from high-intensity cognitive tasks or negative rumination, allowing the prefrontal cortex, which is responsible for executive functions, to rest. This alleviates mental fatigue and stress, which are critical factors in reducing depression risk[40]. Research confirms that when natural landscapes incorporate water, their aesthetic appeal and relaxation effects significantly increase, a phenomenon equally applicable to adolescents[41].

The mental health benefits of blue spaces extend beyond passive observation; they are amplified through physical activity and social interaction, resulting in the formation of an integrated “blue gym”[42]. Compared with ordinary environments, blue spaces offer attractive venues for activities such as swimming, boating and beach sports. These pursuits not only directly improve mood by promoting the release of neurotransmitters such as dopamine and serotonin[43] but also may extend exercise duration through the perception of “time dilation” associated with waterfront settings[44]. The combination of sustained physical activity and the inherent stress-reducing effects of coastal environments can further enhance sleep quality, thereby indirectly promoting mental health[45]. Simultaneously, open water areas, such as beaches and lakeshores, naturally become hubs for social gatherings. Adolescents who participate in group games or family reunions in these settings can effectively strengthen their social support networks and enhance their sense of belonging and self-identity, all crucial psychosocial resources for resilience against depression[46].

While research directly targeting adolescents remains nascent, existing evidence preliminarily reveals associations between blue spaces and mental health[36,47]. A large-scale survey indicated that coastal environments slightly outperform woodland and mountain landscapes in terms of self-rated mental health resilience, suggesting that blue spaces may possess unique emotional restorative functions[48]. Stronger direct evidence comes from a Canadian cross-sectional study of adolescents (n = 29784; age 11-15 years), which revealed that among girls, exposure to outdoor environments (> 0.5 hour/week) was significantly associated with reduced psychosomatic symptoms (odds ratio = 0.76, 95% confidence interval: 0.60-0.95; calculated from a 24% reduction)[13]. Notably, this protective effect is not unconditional. Its ultimate impact is jointly moderated by individual traits (such as interest in water activities) and environmental factors (including accessibility, safety, and the quality of blue spaces). These factors collectively affect the frequency, duration, and quality of adolescents’ blue space experiences, thereby influencing their mental health benefits[49,50].

Negative factors

Short-term impacts: The impact of natural disasters, i.e., extreme adverse events in the natural environment, is often concentrated on adolescents’ mental health within a short timeframe[51]. Research indicates that tornado exposure and subsequent stressors commonly induce adverse mental health symptoms in both adult and child populations, with posttraumatic stress disorder (PTSD), depression, and anxiety being particularly prominent[52]. Studies examining tornado-affected areas across the United States revealed an overall prevalence of 3.7% for PTSD combined with major depressive episodes among adolescents. Further analysis of data from 2000 tornado-exposed adolescents (cross-sectional; mean age = 14.5 years) revealed that depressive symptoms were prevalent, particularly among females, and were significantly associated with lower levels of social support and higher degrees of exposure (P < 0.05)[53]. These findings indicate that under the impact of tornadoes, adolescents’ mental health is influenced by multiple interacting factors, with females and adolescents from low-income families being more vulnerable to psychological distress[54]. Earthquake disasters similarly inflict severe psychological trauma on adolescents. Taking the 2008 Wenchuan earthquake in China as an example, a longitudinal study of Han Chinese adolescents reported a higher prevalence of depression among students 12 months post-disaster[55]. Adolescents’ psychological trauma from earthquakes stems from multiple sources: Witnessing the death or injury of classmates, teachers, or relatives; sustaining physical harm or even becoming disabled; experiencing the destruction of familiar living and learning environments; losing emotional and material support; and enduring physical and mental anguish while awaiting rescue[56]. These factors collectively trigger complex psychological responses in adolescents postdisaster, including fear, numbness, denial, grief, and depression. Some adolescents may even develop suicidal thoughts[57,58]. Natural disasters such as tsunamis and volcanic eruptions also inflict immediate psychological trauma on adolescents. The suddenness and devastating force of tsunamis instantly confronts young people with life-threatening situations, resulting in the loss of home and bereavement. Such intense stressors readily trigger acute stress disorders, manifesting as emotional volatility, insomnia, and anxiety[59]. Volcanic eruptions, accompanied by ash and lava flows, not only devastate the surrounding environment but also worsen air quality and constrict living spaces. This triggers negative emotions, such as fear and helplessness, in adolescents, disrupting their daily lives and academic performance[60].

Additionally, during floods, adolescents may experience anxiety and depression because of submerged homes and property loss, leading to sleep disturbances and difficulty concentrating. The sudden onset of floods strips adolescents of a sense of control over their life, leaving them anxious about an uncertain future. If this psychological pressure is not promptly alleviated, it may escalate into more severe mental health issues[61]. Although not a traditional natural disaster, the pandemic, as a global public health event, shares similarities with crises triggered by environmental changes in its impact on adolescent mental health. Home isolation caused by the pandemic led to a decrease in physical fitness and restricted social activities among adolescents. Research has indicated that compared with the prepandemic average, the incidence of PTSD among adolescents was greater during the early stages of the pandemic[62,63]. These findings demonstrate that sudden environmental upheavals, either natural disasters or public health crises, can disrupt adolescents’ psychological equilibrium in the short term, triggering various mental health issues.

Long-term impacts: The impact of natural disasters and environmental degradation on adolescent mental health extends beyond short-term stress responses. In the long term, these events may lead to chronic, persistent psychological issues that profoundly influence adolescents’ developmental trajectories and adult mental health outcomes[64]. From a disaster trauma perspective, adolescents who experience major natural disasters such as earthquakes, tsunamis, or hurricanes may develop persistent or worsening PTSD if they do not receive effective psychological intervention during the critical recovery period following the disaster[65]. Chinese studies indicate that students in disaster-affected areas exhibit prominent issues such as compulsive behaviors, hypersensitivity in interpersonal relationships, anxiety, depression, hostility, and fear[66]. These persistent psychological problems not only disrupt adolescents’ current studies and daily lives but also may impact their personality development, increasing the risk of personality disorders in adulthood. Such disorders manifest as difficulty understanding and adhering to social norms, along with an inability to establish healthy interpersonal relationships[67,68]. Chronic stress from environmental degradation similarly threatens adolescent mental health. Climate change-induced increases in extreme weather events, such as prolonged heatwaves, droughts, and torrential rains, expose young people to persistently unstable, high-stress environments[69]. As the first generation grows amid rising global temperatures, contemporary adolescents face significant mental health risks from climate change that cannot be overlooked[70]. Prolonged exposure to high temperatures may impair adolescents’ emotional regulation ability, leading to irritability, anger, depression, and other emotional issues[71]. Moreover, food crises and flooding caused by droughts and torrential rains subject adolescents to survival pressures, resulting in anxiety and helplessness. If these negative emotions accumulate over time, individuals may develop chronic mental illnesses.

Changes in the natural environment during urbanization also have long-term latent effects on adolescent mental health. When adolescents are forced to leave familiar living environments due to urban expansion and to switch to a new school, they experience disruption of their existing social networks. Rebuilding social support systems in new settings is challenging and often leads to feelings of loneliness and a lack of belonging[72]. Simultaneously, adapting to new school systems, teaching methods, and cultural differences may cause identity conflicts, with some adolescents developing feelings of inferiority with regard to their backgrounds[73,74]. Family instability, such as parents facing economic transition pressures due to relocation and consequently reducing emotional support for their children, further diminishes adolescents’ sense of security. If these chronic stressors remain unaddressed, they may lead to emotional issues, social difficulties, and low self-esteem among adolescents[75]. These problems can persist into adulthood, affecting career development, family life, and other aspects of life. Furthermore, prolonged exposure to polluted natural environments can subtly affect adolescents’ mental health. Air pollution not only harms adolescents’ physical health but also may disrupt their emotional and cognitive functions by affecting the secretion and regulation of brain neurotransmitters. Research indicates that adolescents who are chronically exposed to high concentrations of PM2.5 have significantly higher scores for depression and anxiety symptoms than those living in areas with good air quality. Furthermore, their cognitive development may be suppressed to some extent[76].

INFLUENCING FACTORS OF NATURE ON ADOLESCENT DEPRESSION

Physical activity

Multiple studies indicate that increasing children’s and adolescents’ exposure to nature has a positive effect on their mental health[77]. Physical activity serves as the most clearly defined behavioral mediator between the natural environment and adolescent depression[78]. Its core mechanism lies in nature’s capacity to significantly increase adolescents’ physical activity frequency and intensity by providing suitable spaces and positive sensory experiences. Regular physical activity subsequently reduces the risk of depression through pathways such as neuroendocrine regulation and improvements in cognitive function[79]. This mediating pathway essentially constitutes a chain reaction of “environmental attractiveness, behavioral change, psychological benefits”, with natural environments offering irreplaceable promotion of physical activity. From an environmental perspective, green spaces and blue spaces provide adolescents with diverse physical activity settings, including walking, running, cycling, ball games, and nature exploration[80]. Unlike indoor spaces or paved surfaces in urban settings, natural environments offer “aesthetic pleasure” through their colors and sounds. Combined with “low-stress attributes”, such as reduced noise and interpersonal interference, these features further stimulate adolescents’ willingness to engage in such activities[81]. For example, compared with exercising on noisy streets, running in a lush park reduces adolescents’ resistance to exercise and extends their activity duration. A German cohort study of adolescents (longitudinal; n = 1192; age 15 years) further confirmed that residing in a neighborhood with higher greenness (normalized difference vegetation index) was associated with significantly more leisure moderate-to-vigorous physical activity among rural dwellers (8% increase; P < 0.05). This increased activity was significantly negatively correlated with lower depression scores, directly confirming the role of nature in alleviating depression through the promotion of physical activity[82]. By controlling for confounding factors such as genetic background and the family environment, Cohen-Cline et al[83] reported that adolescents who accessed green spaces more frequently exhibited higher physical activity levels and a significantly reduced incidence of depressive symptoms.

Social interaction

Natural environments can alleviate depressive moods by fostering positive social interactions, which provide adolescents with emotional support and a sense of belonging, a key interpersonal mediating pathway[84,85]. Unlike the enclosed, fragmented social settings of urban areas, natural spaces possess “openness and sharing” and “activity inclusivity”, breaking down interpersonal barriers and creating more opportunities for face-to-face socializing. High-quality social interaction serves as a vital psychological resource against depression. Particularly during adolescence, a “socially sensitive phase”, social experiences in natural settings are more likely to foster positive self-identity. Mechanistically, nature’s promotion of social interaction manifests in two ways. First, natural environments provide a “neutral medium” for group activities. When adolescents jointly participate in activities such as picnics, tree planting, or nature observation in parks, they experience lower social pressure, facilitating relaxed and equal interactions. Birch et al[86] reported that adolescents perceive community green spaces as “safe social havens”. Exploring nature with peers fosters emotional experiences of “being understood” and “accepted”, effectively reducing loneliness. Second, nature’s “restorative qualities” enhance individuals’ social willingness and capacity. Dopko et al[87] randomly assigned adolescents to either a “nature school group” or a “space museum group”. While physical activity levels did not significantly differ between groups, the nature school group presented a higher frequency and better quality of peer interactions. These findings directly indicate that time spent in nature more effectively enhances children’s positive emotions.

Positive psychological experiences

By stimulating positive psychological experiences in adolescents, natural environments can directly buffer depressive symptoms, a crucial mediating pathway at the subjective experience level[88,89]. Unlike the previous pathways, positive psychological experiences emphasize “optimizing internal psychological states”. Natural environments enhance adolescents’ subjective well-being by fulfilling their emotional and existential needs. High levels of well-being significantly reduce the likelihood of depression, forming a chain of transmission: “nature exposure, positive experiences, depression alleviation”. With respect to overall well-being enhancement, a connection to nature is strongly positively correlated with adolescents’ subjective well-being, demonstrating cross-context consistency. From the perspective of specific positive psychological experiences, the role of the natural environment can be broken down into three aspects. First, in the context of positive emotions, experiments by Oh et al[90] revealed that adolescents reported significantly lower levels of negative emotions after viewing nature photographs. Koselka et al[91] compared the effects of “forest walks” and “urban walks” and reported that forest walks produced more pleasant moods, whereas urban walks generated more negative moods. Similarly, Litleskare et al[92] proposed that exposure to nature helps individuals detach from distress and activates positive emotional responses. Chawla et al[93] proposed that natural environments contain abundant objects that can immerse adolescents, enabling them to achieve their goals more effectively. In summary, numerous studies indicate that children and adolescents experience reduced levels of stress, anger, depression, anxiety, and loneliness and exhibit greater vitality and happiness after they interact with nature[94]. Furthermore, a synthesis of research evidence reveals that stress reduction serves as the primary mediator linking natural contact to mental health[95]. Second, to enhance rational decision-making ability, Berry et al[96] randomly assigned college students to three groups and reported that participants exposed to natural imagery made more rational decisions. Third, with respect to building security and psychological resilience, Coyne and Whiffen[97] reported that while individuals with depression often experience deep-seated insecurity, natural environments provide adolescents with a “sense of refuge”. Furthermore, research by Marselle et al[98] demonstrated that natural experiences provide adolescents with opportunities to engage in activities and develop skills. This, in turn, enhances psychological resilience by fostering self-esteem, competence, confidence, and self-efficacy, thereby further refining the mediating pathways of positive psychological experiences. Wood and Smyth[99] also reported that childhood exposure to nature has a “long-term spillover effect” on adult well-being, providing sustained buffering against depressive symptoms later in life. This discovery offers long-term evidence supporting the pathway through which the natural environment influences adolescent depression via positive psychological experiences.

MODERATING FACTORS OF NATURE’S INFLUENCE ON ADOLESCENT DEPRESSION

Individual factors

Gender: Gender significantly influences the protective effect of nature on depression by moderating adolescents’ patterns of nature exposure, emotional sensitivity, and psychological needs. This moderating effect exhibits “context specificity” across studies[100]. Larsen et al[31] reported that higher levels of greenery in males’ childhood residential environments were associated with a decrease in externalizing symptoms, such as aggression and impulsivity, over time during adolescence. In contrast, no such association was observed in females. Conversely, a cross-sectional study conducted across 45 Chinese universities revealed that campus green spaces significantly alleviated depressive symptoms more effectively among male university students than among female university students. This disparity may stem from men’s greater need for “spatial openness” and women’s more substantial reliance on “social support”[101]. Sarkar et al’s study[102] of 94879 individuals in the United Kingdom revealed that green spaces offer greater protection against the risk of depression among women. This may stem from women being more susceptible to depression triggered by accumulated stress, with nature’s stress-reducing effects being more pronounced in highly sensitive populations. Furthermore, gender modulates adolescents’ natural engagement behaviors. Wheeler et al[103] used GPS and accelerometer monitoring and reported that boys engage in physical activity significantly more often in green spaces than in nongreen outdoor areas. Girls, however, tend to engage in “low-intensity socializing” in green spaces. These behavioral differences may further differentiate the moderating effect of nature on depression, boys alleviate depression through “nature + physical activity”, whereas girls gain psychological benefits from “nature + social support”. However, regardless of gender, “perceived importance of nature exposure” positively moderates the protective effects of nature, adolescents who value nature exposure more often exhibit lower rates of physical and mental symptoms, suggesting that subjective cognition may mitigate gender differences[13].

Behavioral problems: Adolescent behavioral issues, including hyperactivity, aggression, and rule breaking, serve as key moderators of nature’s protective effects, resulting in “greater benefits for high-risk groups”. Research shows that children with behavioral problems benefit most readily from nature. A comparative experimental study revealed that emotionally distressed children and adolescents experience the most substantial restorative effects in natural settings, a phenomenon termed the “amplification mechanism of protective effects”. Research indicates that adolescents with behavioral issues perceive natural spaces as “safe zones free from evaluative pressure”. In nature, they avoid being negatively labeled for their behavior by others and more readily develop a “sense of self-efficacy” through exploration. This positive experience significantly reduces self-denial and depressive emotions stemming from behavioral problems[104]. Previous studies have demonstrated that natural environments can lower depression risk among adolescents with behavioral issues by reducing rumination[105]. Simultaneously, autonomous exploration activities enhance their “sense of behavioral control”, thereby reducing depressive mood stemming from a “sense of loss of control”[106].

Environmental factors

Socioeconomic status: Socioeconomic status (SES) is a key environmental variable that moderates the association between the natural environment and adolescent depression. Cross-sectional studies consistently demonstrate a “priority protective effect” of natural environments for low-SES adolescents across multiple settings. Mitchell et al[107] reported that adolescents from low socioeconomic backgrounds presented lower rates of depressive symptoms after regular exposure to nature than did those without such exposure. Longitudinal studies further validate the stability and causal nature of SES as a moderator of health outcomes. Geary et al[108] revealed that while green spaces have a positive effect on mental health across socioeconomic groups, the effect is strongest among the poorest populations. Compared with that in high SES groups, the association between green space exposure and reduced depression risk was stronger among the poorest individuals, and this difference remained significant after socioeconomic changes were adjusted for during follow-up[109]. Studies focusing on adolescents have reached consistent conclusions: Liu et al’s analysis[110] of a nationwide Chinese adolescent sample revealed that school green spaces significantly alleviated depressive symptoms more effectively among adolescents from economically disadvantaged families than among those from economically advantaged families. This moderating effect remained consistent across different regions and educational levels. Furthermore, Joung et al[111] revealed physiological evidence: Adolescents from low socioeconomic backgrounds presented significantly greater activation intensity in the prefrontal cortex after viewing forest landscapes than did those from high SES backgrounds did, indicating more pronounced neuropsychological benefits derived from natural exposure.

Population density and urbanization: Population density and urbanization levels significantly moderate the protective effect of nature against depression among adolescents by altering the “scarcity” and “stress background” of natural environments. Specifically, higher population density and urbanization levels increase the depression-alleviating effects of nature, a phenomenon termed the “environmental stress compensation mechanism”. In terms of population density regulation, Lederbogen et al[112] reported that high-density urban environments impose greater stress and social demands on residents. From the perspective of urbanization moderation, the urbanization process amplifies the “protective value” of natural environments by reducing natural spaces and increasing psychological stress[88]. Urban densification decreases the availability of private and public green spaces, leading to greater depression risks among urban adolescents than among their rural counterparts. Research has confirmed that urban living is a risk factor for poor mental health among adolescents. In contrast, natural spaces, acting as “antidotes to urban stress”, exhibit more pronounced depressive relief effects among urban youth[113]. Moreover, the “landscape design” of urban environments further modulates the effects of nature. Continuous, open urban green spaces significantly outperform fragmented, enclosed green spaces in alleviating depression, providing evidence for optimizing natural space layouts in urban planning[114].

Role of sunlight: Sunlight exposure in natural settings acts as a “hidden factor” regulating the association between nature and depression. The protective effect of natural exposure on depression among adolescents partially relies on the “added value” of sunlight exposure, particularly through indirect mechanisms involving vitamin D synthesis and mood regulation. Consequently, varying levels of sunlight exposure lead to different depression-alleviating effects[115]. Sunlight exposure is the primary pathway for human vitamin D synthesis[116]. Low vitamin D levels are significantly associated with increased depression risk among adolescents[117]. Thus, natural environments exert indirect protective effects through the “sunlight-vitamin D-depression alleviation” pathway. A cross-latitude study by Marqueze et al[118] further confirmed a significant negative correlation between sunlight duration and adolescent depression incidence. Additionally, sunlight exposure modulates the effects of nature through “nonvitamin D pathways”: Blue light in sunlight suppresses melatonin secretion, improving adolescents’ sleep quality[119]. Simultaneously, sunlight exposure activates the serotonin system in the brain, directly enhancing positive emotions, both mechanisms amplify the antidepressant effects of nature[120]. Consequently, in seasons or regions with abundant sunlight, natural exposure has more pronounced protective effects against depression among adolescents. Conversely, during overcast weather or in high-latitude areas, maximizing the psychological benefits of nature requires combined interventions of “nature exposure + artificial light supplementation”[121].

IMPROVEMENT STRATEGIES

Optimizing the natural environment provision

The “accessibility” and “quality” of natural environments are fundamental prerequisites for their depression-alleviating effects. Campus-centered efforts should collaborate with surrounding communities to create multitiered, highly adaptable green space systems, reducing the temporal and spatial costs of natural encounters among young people. Within campuses, the green space layout should be optimized on the basis of the principle of “balancing functionality and ecology”. On the one hand, idle campus areas should be utilized to plan “micronature spaces”, such as “secret gardens” for growing herbs and flowers or small ecological wetlands with aquatic plants and fish. These factors provide adolescents with private settings for emotional relaxation while enriching their natural experiences through biodiversity. On the other hand, open lawns and tree-lined green spaces should be expanded around playgrounds and teaching buildings equipped with resting benches and nature observation points to meet diverse needs for natural engagement during recess and group activities. Around campuses, enhanced coordination between municipal and education departments is essential. Priority should be given to the development of “pocket parks” and “slow-paced greenways” within the school’s catchment area that link community green spaces and urban parks to form a continuous green pedestrian network. Simultaneously, “child-friendly” upgrades to surrounding green areas, such as adding nature education signage and safety barriers, should be implemented to ensure that young people can conveniently and safely engage with nature during commutes and weekend leisure, thereby achieving “routine nature exposure”.

Promotion of nature-based interventions

Nature-based interventions should be integrated into the school education system. “Curriculum-based integration” is combined with “personalized guidance” to encourage young people to engage in active nature experiences, transforming the psychological benefits of the natural environment into personal emotional regulation skills. At the curriculum level, nature education should be formally incorporated into teaching plans. For example, primary and secondary schools could offer 1-2 weekly “nature and mental health” weekly courses covering topics such as “nature-based emotional awareness”, “nature-inspired artistic expression”, and “natural science understanding”. These courses should adopt a dual-classroom model of “outdoor practice + indoor reflection” to ensure deep integration of theoretical knowledge and experiential learning. Higher education institutions can offer elective courses on nature-based healing, collaborating with botanical gardens and forest parks for field-based instruction to cultivate young people’s ability to utilize natural resources for self-psychological adjustment. For mental health counseling, innovative interventions in natural settings are needed: Installing “outdoor counseling booths” in campus green spaces to guide adolescents with mild depression or anxiety via techniques such as “nature meditation” and “nature imagery reconstruction”. The calming atmosphere of natural environments reduces psychological defenses, thereby increasing the effectiveness of counseling and therapy. During high-stress periods, such as exams and college admissions, individuals consider organizing “nature group counseling activities”, such as forest hikes and team nature scavenger hunts. These activities combine natural experiences with teamwork to release pressure and strengthen group cohesion. Simultaneously, “personalized nature intervention prescriptions” should be developed for adolescents with specific needs, the weekly nature exposure duration and recommended settings of which should be specified to increase intervention precision.

Strengthening family and social support

Sustaining nature interventions requires joint family and societal participation. By integrating resources and disseminating scientific principles, we foster a “whole-person, whole-process” nature-based mental health ecosystem. At the family level, parental awareness and behavioral guidance must be strengthened. Schools can utilize parent education programs and online lectures to disseminate knowledge on topics such as “the protective effect of nature exposure on adolescent depression” and “the synergistic effects of screen time control and nature exposure”. Such programs encourage 1-2 parent-child nature activities per week and can help parents reduce adolescents’ electronic device usage. Parents should also be encouraged to lead, for example, through active participation in nature experiences. Keeping a “family nature journal” to document shared nature experiences and emotional changes can strengthen the family’s natural interaction environment. At the societal level, government departments should incorporate “adolescent nature-based mental health” into public health and urban planning systems. Urban green space planning should prioritize securing natural activity areas for adolescents. Moreover, policies such as free admission days to nature reserves for youth and subsidies for nature-based educational programs should be introduced. Nonprofit organizations and businesses can jointly launch “nature-based healing public benefit projects” and establish a “nature-based mental health service platform” to integrate resources, including psychologists and nature educators, and offer nature intervention consultations and activity reservations. Social media and short video platforms can be utilized to disseminate scientific knowledge on nature-based mental health, enhancing societal awareness and acceptance of nature interventions. To provide a comprehensive overview of the relationships discussed above, Table 1 summarizes the core environmental factors, mediating mechanisms, and moderating variables identified in the literature.

Table 1 Overview of reviewed studies by research dimension.

Category	Specific factors	Key findings/mechanisms	Ref.
Core factors	Green space (positive)	Reduces physiological stress, restores attention (attention restoration theory), and builds social capital	Markevych et al[27]; James et al[28]; Bloemsma et al[30]; Larsen et al[31]
		Long-term exposure in childhood predicts lower depression in early adulthood
		Ecological quality (e.g., biodiversity) matters more than quantity
	Blue space (positive)	Provides “soft fascination” and sensory stimulation (sound of water)	Gascon et al[50]; Pasanen et al[42]
		“Blue gym” effect: Promotes water-based physical activities
		Reduces internalization problems (depression/anxiety)
	Natural disasters (negative)	Short-term: Tornadoes, earthquakes, and floods trigger acute stress, posttraumatic stress disorder, and depression	Paul et al[52]; Feng et al[55]; Meltzer et al[64]; Proulx et al[70]
		Long-term: Disruption of social support and chronic stress from climate change lead to persistent psychological issues
Mediating mechanisms	Physical activity	Nature increases frequency/intensity of exercise (“environmental attractiveness”)	McCormick[77]; Lubans et al[78]; Thompson Coon et al[79]
		Neuroendocrine regulation through active behavior
	Social interaction	Nature serves as a “safe social haven” and “neutral medium”	Sugiyama et al[84]; Birch et al[86]
		Enhances social cohesion and reduces loneliness
	Positive psychological experiences	“Optimizing internal states”: Reduces rumination and enhances subjective well-being	Bratman et al[88]; Liu et al[89]; Marselle et al[98]
		Builds psychological resilience and self-efficacy
Moderating variables	Individual factors	Gender: Context-specific results (e.g., males benefit more from physical activity in nature; females from social support)	Larsen et al[31]; Liu et al[101]; Bratman et al[106]
		Behavioral problems: “Amplification effect”, adolescents with behavioral issues benefit more from nature’s nonjudgmental setting
	Environmental factors	SES: “Priority protective effect”, nature benefits low-SES adolescents more significantly	Mitchell et al[107]; Geary et al[108]; Beyer et al[115]; Anglin et al[116]
		Urbanization: “Stress compensation”, nature acts as an antidote to high-density urban stress
		Sunlight: Regulates vitamin D synthesis and circadian rhythms

SES: Socioeconomic status.

DISCUSSION AND FUTURE RESEARCH DIRECTIONS

As a key ecosystem factor influencing adolescent depressive symptoms, the natural environment has a pronounced “double-edged sword” effect. On the one hand, green spaces and blue spaces, with their unique ecological and sensory attributes, collectively serve as protective carriers that alleviate cognitive fatigue and regulate emotional states. On the other hand, natural disasters such as tornadoes, earthquakes, and floods have become potential sources of threats that induce or exacerbate adolescent depression through acute traumatic stress or prolonged environmental deprivation (Figure 1).

Figure 1 The mechanism of nature-adolescent depression. PA: Physical activity; SES: Socioeconomic status; ADHD: Attention-deficit hyperactivity disorder.

An in-depth analysis of nature’s protective mechanisms revealed that physical activity, social interaction, and positive psychological experiences form the core mediating pathways through which the natural environment influences adolescent depression. By providing diverse activity settings, the natural environment promotes regular physical activity, which in turn alleviates depression by regulating neuroendocrine functions. Simultaneously, the openness and inclusivity of natural spaces foster equitable social interactions, helping adolescents strengthen social support and a sense of belonging, thereby effectively reducing loneliness. Furthermore, exposure to nature directly stimulates subjective well-being, enhances cognitive function, and suppresses negative cognitive patterns, such as rumination, forming a complete chain of transmission: “nature exposure, positive psychological experiences, depression alleviation”. These three pathways are not independent but synergistically interact, collectively constructing the protective effect of the natural environment on adolescent mental health.

However, this protective effect is not uniform; both individual and environmental factors modulate its intensity and pathways in complex ways. At the individual level, gender differences emerge: Girls may benefit more readily from nature’s direct stress-reducing effects. Moreover, boys tend to alleviate depression through the combined pathway of “nature + physical activity”. Additionally, adolescents with behavioral issues may exhibit an “amplified protective effect” mechanism, where they experience more pronounced emotional recovery from nature exposure. At the environmental level, SES modulates this effect, revealing a pattern where “lower SES groups benefit more”. This may stem from the greater marginal psychological benefit of single exposures for low-SES youth, who often have relatively scarce opportunities for natural contact. Simultaneously, urbanization levels play a crucial role: In high-density urban environments, the depressive-alleviating effects of nature (the “environmental stress compensation” effect) typically surpass those in rural areas. Furthermore, sunlight, often an overlooked “latent moderator”, indirectly amplifies nature’s protective effects by promoting vitamin D synthesis and improving sleep quality. This is particularly relevant in high-latitude regions with insufficient daylight, where combined interventions, such as “natural exposure + artificial light supplementation”, warrant exploration.

While the therapeutic potential of nature is evident, translating these findings into equitable and effective public health interventions requires a critical examination of existing barriers. First, equity and access remain formidable challenges. The “green gap”, the disparity in the quality and accessibility of natural environments, often mirrors socioeconomic inequalities. Adolescents in low-income or high-density urban areas may face structural barriers such as safety concerns, a lack of maintenance, or physical distance, preventing them from accessing high-quality green spaces. Without addressing these environmental injustices, nature-based interventions risk benefiting only the privileged, thereby exacerbating rather than mitigating health inequalities. Second, the issues of dosage and specificity warrant rigorous scrutiny. Although current research confirms the benefits of nature, the precise “dose-response” relationship remains elusive. It is unclear what frequency, duration, and intensity of exposure (e.g., “20 minutes in a park” vs “weekend forest immersion”) are required to elicit clinically significant improvements in depressive symptoms. Current evidence on this relationship among adolescents remains fragmented. While Piccininni et al[13] identified a potential minimum threshold, finding that engaging with nature for as little as 30 minutes per week was associated with significant mental health benefits for adolescent girls, evidence regarding an upper limit or “plateau”, where increased exposure yields no further benefit, remains absent. To address this gap, future research, particularly randomized controlled trials, should adopt designs with multiple exposure arms (e.g., 0, 60 minutes/week, and 120 minutes/week) to precisely map the dose-response curve. Furthermore, not all of nature is equal; the specific impacts of environmental quality, quantified by validated metrics such as tree species richness or the natural environment quality score, vs “blue spaces” on adolescent mental health likely differ. However, current guidelines often treat “nature” as a monolithic entity without distinguishing these specific attributes. Finally, the integration of nature into health systems involves tension between standardization and flexibility. Evidence-based medicine typically demands standardized protocols to ensure reproducibility. However, the restorative power of nature often stems from unscripted, autonomous exploration and the unique, subjective connection an individual forms with the environment. Imposing overly rigid protocols may strip nature engagement of its intrinsic motivation and meaning. Future implementation strategies must therefore use a “structured flexibility” approach, establishing safety and minimum duration guidelines while endowing adolescents with agency to interact with nature in personalized ways.

As the risks of “nature deficit disorder” and adolescent depression have risen globally in tandem, uncovering and harnessing the protective value of nature has gained critical public health significance. Future research and practice should evolve toward precision and systematization, expanding nature-based interventions from universal prevention to personalized treatment. Although existing research has established a foundation for the association between the natural environment and adolescent depression, significant room for expansion remains. Future research and practice must evolve toward precision and systematization, guided by specific, testable hypotheses.

First, strengthening longitudinal studies and causal inference designs is an urgent priority. Most existing studies employ cross-sectional designs, limiting causal conclusions. Future efforts should prioritize prospective cohort studies to test the hypothesis that cumulative nature exposure during early adolescence serves as a longitudinal buffer against the onset of depressive symptoms in late adolescence. Moreover, rigorous randomized controlled trials are needed to determine the comparative efficacy of different intervention modalities. We propose the specific hypothesis that compared with unstructured nature contact (e.g., casual park visits), structured, goal-oriented interventions (e.g., horticultural therapy or guided forest bathing) yield superior outcomes for adolescents with moderate-to-severe depression because of the added benefits of social scaffolding and professional guidance.

Second, research must explore individual difference moderation mechanisms in greater depth. Future studies should move beyond descriptive analysis to identify the “active ingredients” of nature. Specifically, researchers should test whether specific environmental features, such as high biodiversity, fractal patterns in vegetation, or the presence of water (blue space), independently contribute to stress reduction and mood regulation, distinct from general greenness. Furthermore, studies should investigate neurophysiological moderators, testing the hypothesis that natural exposure downregulates amygdala reactivity more significantly in adolescents from high-stress urban environments than in their rural counterparts, thereby validating “environmental stress compensation” theory. Crucially, given that adolescence (10-19 years) encompasses marked developmental shifts, future analyses should move beyond aggregate data and stratify results into early (10-13 years), middle (14-16 years), and late (17-19 years) adolescence. Such stratification is essential for determining whether specific developmental windows exist where nature-based interventions are most potent (e.g., early adolescence for family-based nature bonding vs late adolescence for autonomous stress relief).

Third, a more comprehensive theoretical framework for mediating mechanisms should be constructed. Current pathways remain incomplete; future studies should employ structural equation modeling to systematically examine sequential mediators. A particularly promising avenue is to test the “old friends” hypothesis, examining whether exposure to diverse soil microbiomes in natural settings mediates improvements in depressive symptoms via the gut-brain axis. Additionally, attention to potential negative impacts is crucial. Future research should evaluate how safety hazards or allergens impact adolescents’ willingness to engage with nature, enabling the development of safer, more tailored intervention strategies. Finally, advancing interdisciplinary and multimethod integration is crucial. We advocate for a mixed-methods research paradigm that combines quantitative rigor with qualitative depth to strike a balance between scientific precision and humanistic care, thereby providing sustainable, nature-based solutions for the prevention and control of global adolescent depression.

CONCLUSION

This narrative review systematically synthesized the complex relationship between natural environments and adolescent depression. The evidence indicates that green and blue spaces exert protective effects against depressive symptoms through three interconnected mediating pathways: Promoting physical activity, facilitating positive social interactions, and fostering beneficial psychological experiences such as stress reduction and enhanced subjective well-being. However, this protective effect is not uniform; it is significantly moderated by individual factors (e.g., gender, pre-existing behavioral problems) and environmental factors (e.g., SES, urbanization level, and sunlight exposure). Notably, lower-SES adolescents and those in high-density urban environments may derive greater marginal benefits from nature exposure, a finding with important implications for health equity.

Despite the promising therapeutic potential, significant barriers remain, including inequitable access to quality green spaces, an incomplete understanding of the dose-response relationship, and the challenge of balancing standardized protocols with the inherent flexibility of nature engagement. Future research should prioritize rigorous longitudinal and experimental designs to establish causality, stratify analyses by developmental stage (early, middle, and late adolescence), and identify the specific “active ingredients” of nature that confer mental health benefits. By advancing toward precision and systematization, nature-based interventions can be effectively integrated into public health and educational systems, offering a sustainable, low-cost strategy for preventing and alleviating the global burden of adolescent depression.

In conclusion, as the global burden of adolescent depression continues to rise alongside increasing urbanization and nature deficit, harnessing the protective power of natural environments offers a sustainable, low-cost, and universally accessible strategy for mental health promotion. By advancing toward precision and systematization, nature-based interventions can be effectively integrated into public health and educational systems worldwide, ultimately contributing to the well-being of future generations.