Biophilic Design Application in School Common Areas: Exploring the Potential to Alleviate Adolescent Depression

Abstract

This study proposes design strategies for incorporating biophilic design into common areas in schools, with consideration of adolescents’ levels of depression. Types of common areas and relevant biophilic design attributes were identified through a comprehensive review of existing literature. Using Stable Diffusion, visual representations of school common areas featuring biophilic elements were generated, and adolescents’ preferences for these attributes were surveyed. The analysis revealed that Weather & View was the most preferred attribute across all types of common areas. Furthermore, adolescents experiencing depressive symptoms showed a higher overall preference for biophilic design elements compared to their non-depressed peers, with notable gender differences within the depressed group. Specifically, those with mild depressive symptoms exhibited generally high preferences, particularly for attributes such as Water, Shape & Form, Image, and Material. Distinct patterns of preference also emerged depending on the specific application characteristics of the design. This study contributes by proposing tailored design strategies for different types of school common areas that reflect adolescents’ emotional profiles. Future research should incorporate multidimensional approaches, including field studies and investigation of user preferences and psychological responses, to further validate and refine biophilic design applications in educational environments.

1. Introduction

Adolescence is a period of rapid physical and mental change, and the experiences formed during this time have a significant impact on later adult life [1]. According to global statistics, approximately 14% of adolescents aged 10 to 19 experience mental health issues, with depression and anxiety disorders identified as leading contributors [2]. Adolescent depression is often misunderstood as a temporary mood swing caused by puberty, and it is difficult to receive a timely diagnosis due to atypical symptoms that differ from those in adults [3]. In addition, severe depression can lead to suicide, and the prevalence rate is higher among females than males [4]. Therefore, the built environment that considers adolescent mental health should be a multisensory design that promotes social, emotional, physical, and intellectual development, and it is important to design spaces so that natural elements such as sunlight and plants can be easily accessed [5]. Furthermore, adolescents with mental illness can be treated more effectively in therapeutic environments that include natural elements, as these settings provide emotional stability and reduce stress, compared to conventional closed psychiatric wards [6].

Schools are the primary physical environments where adolescents spend the majority of their time. Beyond fulfilling their functional role as places of learning, they should also contribute to supporting students’ mental health and well-being through exposure to nature [7]. Historically, school common areas—such as hallways and staircases—were primarily designed to facilitate student movement and were regarded as circulation-focused spaces, with spatial hierarchy and functional intent centered more on transit than on educational engagement [8]. Recently, school common areas have been emphasized as important learning environments that promote various activities, such as social interaction and voluntary collaboration among students, going beyond their basic function of movement. Features of these common areas, such as natural lighting, comfortable furniture arrangement, and open spatial structures, encourage students to perceive them as spaces where they want to stay [9]. As common areas evolve into spaces that foster self-directed learning and social exchange, growing emphasis has been placed on the role of biophilic design in reducing student stress and enhancing academic performance [10]. In this context, the integration of natural elements into school environments—where adolescents spend a significant portion of their time—has been shown to contribute positively to their mental health [11]. Biophilic design, grounded in the idea that humans have an inherent affinity for nature, introduces natural elements into built environments to elicit psychological benefits and enhance user well-being. It has been found to reduce stress, improve concentration, and enhance productivity [12]. This design approach has progressed beyond merely offering physical comfort, toward creating environments that support students’ emotional development and foster deeper learning engagement [13].

In line with this shift, school facility guidelines have begun incorporating biophilic design principles, underscoring the importance of enabling students to learn in settings that maintain a connection to nature [14]. These guidelines highlight biophilic design as a means of maximizing educational benefits, including reduced stress, improved mental well-being, and enhanced academic performance [15]. Collectively, these insights affirm the practical value of biophilic design as an architectural strategy for supporting adolescent mental health within educational environments.

The purpose of this study is to identify adolescents’ needs and preferences for biophilic design characteristics in consideration of depression and, based on the findings, to propose strategies for applying biophilic design in school common spaces. In this study, the term common space refers specifically to circulation-oriented public areas within school buildings, such as corridors, staircases, and central halls. While residential buildings typically distinguish between private and shared zones, all spaces in schools are inherently shared; therefore, the term “common space” in this context is used to indicate non-instructional, movement-centered spaces accessible to all students.

The specific research questions are as follows:

RQ1. 

How do preferences for biophilic design attributes vary across different types of school common areas (hallways, staircases, central halls)?

RQ2. 

How do biophilic design preferences differ by gender, depending on the presence or absence of depressive symptoms?

RQ3. 

Are there differences in preference for the method of biophilic design application (vertical vs. horizontal) according to the level of depression?

RQ4. 

What strategies can be proposed for effectively applying biophilic design in school common areas?

Figure 1 illustrates the methodology and scope of this investigation, which are explicated as follows.

First, a comprehensive literature review was conducted to analyze the levels of depression among Korean adolescents and the relevant assessment scales, examine the current conditions of communal spaces in schools, and explore the psychological effects and key attributes of biophilic design. Second, based on insights from the literature review, simulation images incorporating biophilic design elements into school communal spaces were developed and used as instruments for a structured survey. The identified design attributes were categorized by application surface—vertical (walls) and horizontal (ceilings and floors). Spatial types were classified according to the hierarchy of communication into horizontal (corridor), vertical (stairwell), and collective (central hall) spaces, and one representative space from each category was selected for analysis. The simulations were generated using the image-to-image method of the AI image generation model Stable Diffusion (Web UI), which produces new images by applying textual prompts to specified areas of a source (seed) image. Third, high school students were surveyed to assess their levels of depression using the CES-DC scale and to evaluate their preferences for the biophilic design images. Finally, preference scores were compared and analyzed by depression level, space type, and design attribute, and design strategies for the application of biophilic design in school communal spaces were proposed accordingly.

This study was approved by the Institutional Review Board of Keimyung University. Informed consent was obtained from all participants and their legal guardians prior to data collection. The survey was conducted anonymously, and all responses were de-identified to ensure participant confidentiality. Participation was entirely voluntary, and respondents were informed of their right to withdraw from the study at any time without consequence. To ensure ethical safeguards, the research was carried out in collaboration with school counselors and teachers, who also facilitated access to psychological support if needed.

2. Literature Review

2.1. Adolescent Depression

Depression is a prevalent mental disorder worldwide, characterized by persistent feelings of sadness, anhedonia, and various side effects, and is known to nearly double the risk of mortality [16]. Adolescence is not only a critical period of physical and psychological development, but also a time when the likelihood of emotional disorders and behavioral problems significantly increases, making it a period particularly more vulnerable to depression than other stages of life [17]. Adolescent depression has surfaced as a significant public health concern owing to its considerable prevalence, substantial burden of disease, and elevated rates of recurrence [18]. A recent investigation indicated that the prevalence of depression in the adolescent demographic increased from 1990 to 2019, culminating at 21.67%, while the incidence rate ascended to 19.05% [19]. Notably, the proportion of female adolescents experiencing depression was found to be more than twice that of males, underscoring the severity of adolescent depression as a social issue [20]. Furthermore, adolescents with depression often suffer from comorbid psychiatric disorders such as anxiety and ADHD, and severe depression may lead to suicide, one of the leading causes of death in this age group [21]. In contrast to adults, who typically show classic symptoms of depression such as sadness, emptiness, and hopelessness, adolescents tend to express depression through negative emotions like irritability or grumbling, or through problematic behaviors at school [3]. The risk determinants associated with adolescent depression can be broadly classified into biological, psychological, and environmental domains. Biological determinants include a decline in functional connectivity during adolescence between the amygdala and both the prefrontal cortex, which regulates emotions, and the insula, which is involved in emotional and internal state recognition. This disconnection may impair emotional regulation and reduce social functioning [22]. Psychological determinants such as low self-esteem, negative cognitive distortions, and high levels of anxiety contribute to an increased risk of depression in adolescents, particularly when they are exposed to negative events or stressful situations [23]. Environmental determinants, including school, family, and cultural or physical surroundings, are associated with improved adolescent mental well-being and a reduced risk of depression when characterized by harmonious family relationships, emotional support, and abundant greenery [24,25].

The treatment of adolescent depression should be appropriately tailored using psychotherapy and/or pharmacological interventions based on the severity of symptoms, developmental level, and associated risk factors. It is essential that caregivers are educated regarding the benefits and risks of treatment, precautions for monitoring, and follow-up care strategies [26]. Despite the availability of effective interventions, treatment rates among adolescents remain low, primarily due to the high cost of care and concerns about social stigma and family reactions [27]. In many cases, depression that begins in early adolescence is not promptly addressed, leading to symptom chronicity and potentially disrupting critical life transitions in adulthood, including interpersonal relationships and marriage. This underscores the importance of early detection and timely intervention [28]. Architectural elements effective in alleviating depression include six key components: nature-centered spaces, concentrated social spaces, diverse spaces, visual comfort, logical processes, and safe spaces. Among these, naturalism has been identified as the most effective element in generating and enhancing patient vitality [29]. Additionally, exposure to nature, such as natural light or plants, can help reduce patients’ stress levels and increase their satisfaction with treatment, and in particular, the physical environment for healing should be designed as a multisensory space that stimulates sight, hearing, smell, and touch [30].

Representative instruments for assessing adolescent depression include the Children’s Depression Inventory (CDI), Beck Depression Inventory (BDI), Reynolds Adolescent Depression Scale (RADS), and the Center for Epidemiological Studies Depression Scale (CES-D) [31,32,33,34]. Shahid et al. [35] developed the Center for Epidemiological Studies Depression Scale for Children (CES-DC), a self-report instrument adapted from the adult version (CES-D) using simpler and more accessible language suitable for children and adolescents based on their developmental levels [36]. The CES-DC comprises 20 items, each rated on a four-point Likert scale, assessing the respondent’s mood and behavior over the past week [35]. Based on scoring criteria like those of the CES-D, a cutoff score of 16 is typically used: scores of 0–15 indicate a normal range, 16–20 mild depression, 21–24 moderate depression, and 25–60 severe depression [34,37,38,39,40]. Accordingly, this study employs the CES-DC to assess the level of depression among adolescent participants.

2.2. School Common Areas Design

Schools serve as environments where adolescents establish their identities and grow through learning, exerting a significant influence on their overall development [41]. They also provide safe and supportive social and academic settings, playing a vital role not only in adolescents’ daily lives but also in shaping their long-term quality of life [31]. Serving as facilitators for promoting healthy behaviors and supporting social and emotional well-being, physical structures in an optimal school environment for adolescents encompass both indoor spaces—such as classrooms and corridors—and outdoor areas, including school grounds [42]. A pleasant and safe physical environment enhances adolescents’ educational and psychological outcomes, strengthening academic achievement and aspirations through healthy and positive learning experiences [43]. Functioning as venues that promote social interaction—such as communication and collaboration—among students, school common areas extend the learning environment beyond traditional classrooms and should be designed with flexibility and modularity to accommodate a variety of activities [44]. School common areas can be categorized, based on the hierarchy of communication, into horizontal, vertical, and collective communication spaces, as detailed in

Table 1. Classification according to the hierarchy of communication in school common areas.

Common Areas	Content	Spatial Composition
Horizontal Communication Space	A space where communication between users on each floor takes place	- Corridor - Floor lobby
Vertical Communication Space	A space where communication between upper and lower floors takes place	- Stairwell - Elevator area
Collective Communication Space	A space where horizontal and vertical communication spaces meet, and where central communication throughout the school takes place	- Indoor plaza - Central hall (main entrance)

[45].

Common areas in schools examined in this study can be categorized by type. In this study, one representative spatial type was selected from each category within the hierarchy of communication for empirical analysis. Accordingly, the corridor was chosen as the horizontal space, the stairwell as the vertical space, and the collective hall as the collective space. These spaces were selected for their frequent use and high visibility in students’ daily routines, making them well suited for analyzing the psychological responses to biophilic design elements.

The hallway, representing a horizontal communication space, not only facilitates circulation but also serves as a setting for educational and social interactions among students, necessitating a design that integrates safety, learning, and social engagement [46]. Similar to classrooms, hallways should be recognized as integral educational environments. As some of the most interaction-rich common spaces within schools, they serve as informal learning settings where students develop mutual respect and shared cultural norms [47]. These spaces should be designed to promote psychological vitality, reduce stress, and facilitate positive social interactions [48].

In addition, stairwells—traditionally viewed as vertical circulation spaces—can function as more than just transitional zones. When thoughtfully designed, they can serve as architectural elements that enhance spatial continuity and promote social interaction [49]. By incorporating specific design features such as visual openness, natural lighting, warm color palettes, and safe, tactile materials, stairwells can transcend their utilitarian role. They can become psychologically supportive environments that accommodate informal activities such as learning, play, and rest [50].

The central hall, classified as a collective communication space, is typically located at the core of the school building and is characterized by an open, multistory interior illuminated by a glass ceiling, enabling its use for various purposes such as communication, learning, relaxation, and psychological stabilization [51]. Moreover, the main entrance should not be perceived merely as a closed, surveillance-oriented security zone but should instead be designed to evoke openness and hospitality through the incorporation of glass windows, natural light, vegetation, color schemes, and community-oriented elements, thereby creating an emotionally safe and welcoming environment for both students and visitors [52].

School common areas should function not simply as zones for movement or waiting, but as spaces that enhance students’ social interaction, learning engagement, and emotional well-being, with physical environments tailored to the psychological and social characteristics of adolescent users [53]. In this context, the presence of rich and diverse natural surroundings has been associated with improved academic performance and behavioral outcomes [54], and even passive exposure to greenery—such as viewing natural landscapes through windows—has been shown to accelerate recovery of physiological stress markers like skin conductance and heart rate variability, underscoring the mental health benefits of visual access to green spaces [55].

Furthermore, integrating green environments within common areas supports adolescents’ stress recovery and cognitive vitality, and school environments with increased natural elements contribute significantly to students’ psychological stability and positive learning behaviors [56]. Therefore, nature-oriented design strategies that foster emotional security and facilitate positive learning experiences should be actively considered in the planning of common areas in schools.

2.3. The Effects and Attributes of Biophilic Design

Biophilic design is a design approach that integrates direct and indirect experiences with nature into the built environment, thereby enhancing human health, productivity, and emotional well-being [57]. It also serves as a strategic framework for improving health, well-being, creativity, and performance by restoring the human connection with the natural world [58]. Educational facilities are often characterized by uniform and static spatial layouts, which can lead to emotional and sensory deprivation among students [58]. Therefore, when planning educational spaces, it is essential to incorporate multisensory experiences with nature to support students’ emotional and physical development, as well as their learning and task performance [59]. Within school environments, biophilic design has been shown to enhance the well-being of both students and teachers, offering a wide range of benefits, including reductions in stress, inattention, and hyperactivity symptoms, decreased absenteeism, increased physical activity, improved learning outcomes and academic achievement, and strengthened social behaviors [60]. Kellert classified biophilic design into three categories of experience: direct experience, indirect experience, and experience of space and place [57]. Direct experiences include elements such as natural light, water, and vegetation, while indirect experiences involve symbolic representations of nature, such as imagery and materials. The experience of space and place encompasses psychological impressions tied to local environmental and geographical context such as feelings of shelter and mobility—but may be subject to interpretive ambiguity depending on the function and nature of the space [61].

Table 2. Space planning elements based on biophilic design attributes.

BDA *	Subject to Application	Detailed Planning Elements
Weather & View	Vertical Plane—Wall	Curtain wall or full-face glass
	Horizontal Plane—Ceiling/Floor	Light well or courtyard
Type of Plants & Landscape	Vertical Plane—Wall	Green wall or vertical green
	Horizontal Plane—Ceiling/Floor	Indoor garden or plant decoration
Water	Vertical Plane—Wall	Waterfall space and decoration
	Horizontal Plane—Ceiling/Floor	Water flow space and decoration
Image	Vertical Plane—Wall	Actual and metaphorical images of nature
	Horizontal Plane—Ceiling/Floor	Murals or decorations depicting nature
Shape & Form	Vertical Plane—Wall	Decorations or designs utilizing geometric shapes
	Horizontal Plane—Ceiling/Floor	Decorations or designs utilizing organic shapes
Material	Vertical Plane—Wall	Wall finishes or decorations using natural materials
	Horizontal Plane—Ceiling/Floor	Material elements or finishes inspired by natural landscapes

Note. BDA *: Biophilic Design Attributes.

presents a reorganization of biophilic design planning elements, based on the biophilic experience-based model proposed by Lee, which builds upon Kellert’s original framework [57,62]. Biophilic design can be applied in various ways depending on the surfaces within indoor spaces, including walls, ceilings, and floors [62]. Accordingly, this study categorized the wall surface as vertical and the ceiling and floor surfaces as horizontal and derived applicable planning elements based on these application orientations. The main attributes identified are Weather & View, Type of Plants & Landscape, Water, Image, Shape & Form, and Material, each of which was detailed according to its application target and associated planning components. For example, the Weather & View attribute was implemented through elements such as curtain walls, large glass façades, skylights, or courtyards, while Type of Plants & Landscape was applied via wall-mounted plantings, indoor gardens, and decorative vegetation. The Water attribute included elements such as wall-mounted waterfalls and floor-integrated water features, while Image comprised visual components such as realistic depictions of nature, metaphorical imagery, and murals. Shape & Form incorporated decorative motifs featuring geometric or organic forms, and the Material attribute included surface finishes for walls and floors based on natural materials. These planning elements contribute to users’ psychological stability and their perception of a nature-friendly environment by facilitating indirect experiences of natural elements within indoor spaces.

Recent empirical studies have further elucidated the mechanisms through which biophilic design supports adolescent mental health, particularly in relation to depression. Exposure to natural elements—such as vegetation, daylight, and organic materials—has been shown to reduce physiological stress markers by activating the parasympathetic nervous system, leading to lower cortisol levels and improved emotional regulation [55,63]. In school settings, even passive exposure to nature—such as through classroom windows or atriums—has been associated with reduced student-reported stress, enhanced mood, and improved cognitive functioning [11,56]. A recent study further confirmed that the integration of greenery and natural light in educational environments significantly alleviates depressive symptoms among high school students [64]. Biophilic design can enhance students’ emotional well-being and sense of place, particularly in vertical school settings, as highlighted in a recent study [11]. These findings underscore the role of biophilic environments not only as psychological moderators but also as restorative interventions that help mitigate depressive symptoms and promote mental health among emotionally vulnerable adolescent populations.

3. Survey and Analysis Methods

3.1. Development of Survey Tool

This study developed a survey tool to assess adolescent depression and preferences, based on the previously reviewed CES-DC and biophilic design planning elements. The CES-DC has been validated for use with children and adolescents in diverse cultural contexts and has demonstrated good psychometric properties in previous studies [35,37]. The scale was originally derived from the CES-D developed by Radloff [34], which remains a widely used tool for depression screening in general populations. In this study, the 20 items of the CES-DC scale were applied in their previously validated form, based on the original structure developed by Radloff [34].

Table 3. Items from the CES-DC 20-item scale.

№	CES-DC Item
1	I was bothered by things that usually don’t bother me.
2	I did not feel like eating; I wasn’t very hungry.
3	I felt that I could not shake off the sad feelings even with help from my family or friends.
4	I felt I was just as good as other kids.
5	I had trouble keeping my mind on what I was doing.
6	I felt down and unhappy.
7	I felt that everything I did was an effort.
8	I felt hopeful about the future.
9	I thought my life had been a failure.
10	I felt fearful.
11	My sleep was restless.
12	I was happy.
13	I talked less than usual.
14	I felt lonely, like I had no friends.
15	People were unfriendly.
16	I enjoyed life.
17	I had crying spells.
18	I felt sad.
19	I felt that people disliked me.
20	I could not get going.

presents the full list of CES-DC items.

To apply biophilic attributes, approximately 20 images of school common areas—primarily from Korean middle and high schools—were collected using the Google search engine with keywords such as “school common areas + biophilic design”, and 10 images suitable for the application of biophilic elements to vertical (walls) and horizontal (ceilings and floors) surfaces were selected. The selected images were set as seed images, serving as the original input, and biophilic design applications were generated using the image-to-image method in Stable Diffusion (Web UI). The image-to-image method generates new images based on a prompt by designating specific areas of the seed image for transformation.

Table 4. Seed images and default settings.

Seed Image			Image Generation Values
Corridor	Stairwell	Center Hall
			Sampler	Exponential SDE 2M DPM++
			Image Size	900 × 600
				900 × 1350
				900 × 1143
			Steps	25
			CGP scale	9

presents the seed images and the default parameter settings, while

Table 5. Quality prompts.

Positive Prompt	Negative Prompt
high quality, highly detailed, attention to detail, photorealistic 8k, UHD, HDR, professional photograph, realistic, precise	human, error, bed quality, tiling, sketch, ugly, pixelated, low resolution, high contrast, split image, distortion, text, watermark, name, signature

presents the quality prompts used in the image generation process.

In this study, multiple images were generated using Stable Diffusion for each application characteristic of six biophilic design attributes across three types of common areas, and image selection was conducted through validation by three experts specializing in biophilic design within the fields of architecture and interior design. The evaluation was carried out using a Likert scale, and the specific evaluation criteria—reorganized and synthesized based on relevant prior studies—are presented in

Table 6. Evaluation metrics for biophilic design application images.

Metric	Details
Domain Fidelity	- To what extent do the images accurately represent the attributes of biophilic design? - Do the design elements in the image form a visually coherent and harmonious composition? - Are the biophilic attributes in the image clearly distinguishable and conceptually appropriate?
Visual Clarity and Quality	- Do the images for each space (central hall, stairwell, and corridor) maintain sufficient visual clarity and overall quality, considering resolution differences, to effectively convey biophilic attributes?
Application Orientation Consistency	- Are the biophilic attributes applied appropriately according to their application characteristics—vertically or horizontally?
Attribute Interpretability	- Are the biophilic attributes in the image easily identifiable and distinguishable by observers?
Spatial Realism	- Does the spatial composition and structure appear realistic and architecturally plausible with the applied biophilic elements?

[65,66].

Ultimately, a total of 36 images were produced by applying six biophilic design attributes—both vertically and horizontally—to the three types of common areas, as detailed in

Table 7. Biophilic application simulation image.

TCA *		Biophilic Design Attributes
		Weather & View	Type of Plant & Landscape	Water	Image	Shape & Form	Material
Corridor	Vertical
	Horizontal
Stairwell	Vertical
	Horizontal
Central Hall	Vertical
	Horizontal

Note. TCA *: Type of Common Areas.

.

3.2. Survey Overview and Analysis Methods

This study conducted an online survey over approximately two months, from January to March 2025, targeting 200 high school students aged 16 to 18 from various regions in Korea to investigate adolescents’ levels of depression and their preferences for biophilic design applied in school common areas. Recruitment was conducted through outreach to school counselors and teachers in both urban and suburban areas, and participation was anonymous to ensure privacy and minimize response bias. To ensure balanced demographic representation, a stratified sampling method was applied based on age (16, 17, and 18 years) and gender (male/female). The sample was structured to include a comparable number of participants within each stratum, thereby avoiding over- or under-representation of specific subgroups and enhancing the generalizability and validity of the findings. The collected data were statistically analyzed using SPSS v29 for Windows, and the survey outline and analysis methods are detailed in

Table 8. Survey overview and how to process statistics.

Survey Items	N	Details	Analysis
Depression Scale (CES-DC)	20	4-point scale (0: not at all~3: very much)	Descriptive statistics
		Normal (T < 15), Mild (16 < T < 20), Moderate (21 < T < 24), Severe (25 < T < 60)
Biophilic Design Planning Characteristics Preference	39	Image preference for vertical and horizontal application by biophilic experience attributes : 5-point scale (1: not preferred~5: highly)	Descriptive statistics response sample t-test
General Matters	2	Gender, Age	Frequency analysis

.

The study utilized a structured questionnaire consisting of three parts. First, depression levels were measured using the Center for Epidemiological Studies Depression Scale for Children (CES-DC), which comprises 20 items addressing emotional, cognitive, and somatic symptoms of depression, such as sadness, sleep disturbance, and fatigue. Each item was rated on a 4-point Likert scale ranging from 0 (“Not at all”) to 3 (“Very much”). Based on the total scores (range: 0–60), the participants were classified into four categories: Normal (T < 15), Mild (16 ≤ T < 20), Moderate (21 ≤ T < 24), and Severe (25 ≤ T ≤ 60), following thresholds used in prior Korean validation studies. Descriptive statistics and paired sample t-tests were conducted to analyze depression scores and their relation to design preferences. The full list of CES-DC items used in this study is provided in Table 3. Second, the participants evaluated a total of 39 simulation images—including seed images—depicting school communal spaces with biophilic design attributes applied to either vertical (walls) or horizontal (ceilings and floors) surfaces. Each image was rated on a 5-point Likert scale from 1 (“Not at all preferred”) to 5 (“Highly preferred”). Descriptive statistics and paired sample t-tests were conducted to compare preference scores between original and biophilic design images. Additional t-tests were performed to examine gender-based differences in preference within groups defined by the presence or absence of depression, as well as to compare preferences across levels of depression severity. Finally, general demographic information—specifically gender and age—was analyzed using frequency analysis and paired sample t-tests.

4. Results Analysis

4.1. Characteristics of Participants and Reliability of the Survey Tool

The general characteristics of the participants are presented in

Table 9. General characteristics of the survey subjects.

Division		F (%)
Gender	Male	100 (50)
	Female	100 (50)
Age	16 years	43 (21.5)
	17 years	76 (38.0)
	18 years	81 (40.5)
Total		200 (100)

. Among the 200 respondents, the gender distribution was equal, and the majority age group was 18 years old.

This study examined adolescents’ levels of depressive symptoms to identify their preferences for biophilic design attributes according to depression status.

Table 10. Depression status of survey subjects.

Division			F (%)
Normal	Male		46 (56.8)	81 (40.5)
	Female		35 (43.2)
Depression Level	Mild	Male	24 (51.1)	47 (23.5)
		Female	23 (48.9)
	Moderate	Male	8 (47.1)	17 (8.5)
		Female	9 (52.9)
	Severe	Male	22 (40.0)	55 (27.5)
		Female	33 (60.0)
Total				200 (100)

presents the depressive status of the participants. Among the 200 respondents, 81 (40.5%) were classified as having no depressive symptoms, while 119 (59.5%) exhibited symptoms of depression. Among those with depression, 55 (27.5%) were categorized as having severe depression, followed by 47 (23.5%) with mild depression, and 17 (8.5%) with moderate depression. Overall, more than half of the participants reported experiencing clinically meaningful levels of depressive symptoms, highlighting the importance of analyzing their environmental preferences in relation to psychological responses.

This study conducted a reliability analysis on a total of 59 items related to the adolescent depression scale and preferences for biophilic design attributes, using the alpha coefficient method (Cronbach’s alpha) to assess the internal consistency of the survey instrument. In this study, the CES-DC scale demonstrated high internal consistency for the 20 items measuring adolescent depression (Cronbach’s α = 0.820), while the 39 items assessing preferences for biophilic design also showed excellent reliability (Cronbach’s α = 0.911). Content validity for the image-based preference evaluation was ensured through expert review by three specialists in architecture and interior design. According to established standards in the social sciences [67], both reliability coefficients indicate that the survey instruments used in this study are acceptable and robust.

4.2. Preferences for Biophilic Design Attributes in Common Areas

Table 11. Preference for biophilic design attributes by common area type among all participants.

Preference Survey Items		Type of Common Areas
BDA *	Application Characteristics	Corridor		Stairwell		Central Hall
		M(SD)	t	M(SD)	t	M(SD)	t
Weather & View	Vertical	3.59(0.95)	−0.699	3.43(0.98)	−6.930 ***	3.93(0.79)	2.534 *
	Horizontal	3.65(1.05)		3.97(1.03)		3.73(1.01)
Type of Plant & Landscape	Vertical	2.73(1.17)	−3.078 **	3.31(1.23)	8.851 ***	2.91(1.23)	−7.684 ***
	Horizontal	2.93(1.23)		2.56(1.21)		3.56(1.05)
Water	Vertical	3.55(1.20)	5.555 ***	3.17(1.28)	3.105 **	3.16(1.36)	1.822
	Horizontal	3.06(1.24)		2.94(1.25)		3.01(1.18)
Image	Vertical	3.12(1.09)	5.429 ***	3.39(1.06)	9.700 ***	2.42(1.14)	−3.378 ***
	Horizontal	2.67(1.20)		2.66(1.11)		2.68(1.18)
Shape & Form	Vertical	3.21(1.11)	3.002 **	3.79(1.06)	4.394 ***	3.49(1.13)	4.427 ***
	Horizontal	2.95(1.17)		3.40(1.19)		3.06(1.21)
Material	Vertical	3.64(1.06)	3.256 **	3.50(1.09)	−0.870	3.58(1.21)	−1.024
	Horizontal	3.36(1.15)		3.57(1.08)		3.66(1.02)
Total		3.21(1.14)	-	3.31(1.13)	-	3.27(1.11)	-

Note. * p < 0.05, ** p < 0.01, *** p < 0.001, bold = biophilic design attributes with significantly higher preference, BDA *: Biophilic Design Attribute.

presents the average preferences for biophilic design applications by application characteristics across different types of school common areas, along with the results of paired sample t-tests. The overall analysis of preferences revealed that the average preference scores for the original seed images were 3.08 for the corridor, 3.24 for the stairwell, and 3.26 for the central hall. Although the differences were not large, the images with biophilic design elements applied to the corridor (3.21), stairwell (3.31), and central hall (3.27) all exceeded the midpoint score of 3.0 and showed relatively higher levels of preference compared to the original seed images. When analyzing preferences for specific biophilic attributes by common area type, the corridor showed the highest preferences for ‘Weather & View—Horizontal (3.65)’, followed by ‘Material—Vertical (3.64)’ and ‘Weather & View—Vertical (3.59)’. For stairwells, the highest preferences were found in ‘Weather & View—Horizontal (3.97)’, ‘Shape & Form—Vertical (3.79)’, and ‘Material—Horizontal (3.57)’. The central hall exhibited the strongest preferences for ‘Weather & View—Vertical (3.93)’, followed by ‘Weather & View—Horizontal (3.73)’ and ‘Material—Horizontal (3.66)’. The paired sample t-tests revealed statistically significant differences in preferences across all three spaces for the attributes ‘Type of Plant & Landscape’, ‘Image’, and ‘Shape & Form’. Additionally, significant differences were found between vertical and horizontal applications for Water and Material in corridors, Weather & View and Water in stairwells, and ‘Weather & View’ in central halls. Table 11 shows the preference for biophilic design attributes by common area type among all the participants.

4.3. Preferences for Biophilic Design by Gender According to Depression Status

Table 12. Average difference in preferences for biophilic design by gender in corridor spaces according to depression status.

Preference Survey Items		Normal			Depression
BDA *	Application Characteristics	Male (n = 46)	Female (n = 35)	t	Male (n = 54)	Female (n = 65)	t
		M(SD)	M(SD)		M(SD)	M(SD)
Weather & View	Vertical	3.48(1.07)	3.89(0.80)	−1.889	3.59(0.92)	3.49(0.94)	0.585
	Horizontal	3.70(1.05)	3.51(0.98)	0.791	3.70(1.09)	3.63(1.05)	0.370
Type of Plant & Landscape	Vertical	2.67(1.27)	2.66(1.35)	0.057	2.89(1.06)	2.66(1.11)	1.137
	Horizontal	2.83(1.43)	2.74(1.22)	0.276	3.06(1.17)	3.00(1.15)	0.261
Water	Vertical	3.57(1.31)	3.57(0.95)	−0.024	3.46(1.31)	3.60(1.16)	−0.605
	Horizontal	2.89(1.48)	2.74(1.17)	0.488	3.33(1.20)	3.11(1.09)	1.074
Image	Vertical	3.24(0.99)	2.86(0.94)	1.752	3.43(1.18)	2.91(1.10)	2.480 *
	Horizontal	2.85(1.11)	2.17(1.07)	2.751 **	3.07(1.32)	2.48(1.09)	2.707 **
Shape & Form	Vertical	3.00(1.17)	3.34(1.06)	−1.359	3.20(1.19)	3.29(1.03)	−0.436
	Horizontal	3.04(1.21)	3.06(1.08)	−0.053	3.09(1.15)	2.71(1.18)	1.788
Material	Vertical	3.67(1.14)	3.66(0.97)	0.070	3.69(1.08)	3.57(1.05)	0.594
	Horizontal	3.30(1.19)	3.20(1.05)	0.411	3.69(1.10)	3.22(1.19)	2.219 *
Total		3.19(1.20)	3.12(1.05)	-	3.35(1.15)	3.14(1.10)	-

Note. * p < 0.05, ** p < 0.01, BDA *: Biophilic Design Attribute.

presents the differences in average preferences for biophilic design attributes in the corridor, categorized by gender and the presence or absence of depression. Overall, adolescents with depressive symptoms showed relatively higher preferences for biophilic design compared to those without. Specifically, the average preference scores were 3.35 for males and 3.14 for females with depression, compared to 3.19 and 3.12, respectively, for their non-depressed counterparts.

Among the non-depressed participants, males showed the highest preferences for ‘Weather & View—Horizontal (3.70)’, ‘Material—Vertical (3.67)’, and ‘Water—Vertical (3.57)’, whereas females preferred ‘Weather & View—Vertical (3.89)’, ‘Material—Vertical (3.66)’, and ‘Water—Vertical (3.57)’. For the participants with depression, males rated ‘Weather & View—Horizontal’, ‘Material—Vertical’, and ‘Material—Horizontal’ the highest (all ≥ 3.69), while females showed strong preferences for ‘Weather & View—Horizontal’, ‘Water—Vertical’, and ‘Material—Vertical’ (all ≥ 3.57). Full preference rankings are provided in Table 12.

The paired sample t-tests revealed statistically significant gender-based differences in specific attributes. Among non-depressed individuals, a significant difference between males and females was found for ‘Image—Horizontal’. In the depressed group, gender differences were significant for ‘Image—Vertical’, ‘Image—Horizontal’, and ‘Material—Horizontal’. These results suggest that perceptual differences between males and females—particularly in visual and material-based stimuli—are more distinct under depressive conditions.

In summary, adolescents with depressive symptoms tend to express stronger preferences for sensory-enriched biophilic design attributes. Additionally, gender-based differences in preferences, especially regarding image and material characteristics, indicate the necessity of personalized design strategies that consider both psychological status and gender when designing restorative educational environments.

Table 13. Average difference in preferences for biophilic design by gender in stairwell spaces according to depression status.

Preference Survey Items		Normal			Depression
BDA *	Application Characteristics	Male (n = 46)	Female (n = 35)	t	Male (n = 54)	Female (n = 65)	t
		M(SD)	M(SD)		M(SD)	M(SD)
Weather & View	Vertical	3.39(1.18)	3.66(0.73)	−1.172	3.44(0.98)	3.31(0.93)	0.776
	Horizontal	4.09(1.13)	3.91(1.01)	0.712	3.76(1.03)	4.08(0.97)	−1.729
Type of Plant & Landscape	Vertical	3.35(1.35)	3.29(1.34)	0.205	3.44(1.21)	3.17(1.10)	1.301
	Horizontal	2.67(1.27)	2.54(1.22)	0.469	2.70(1.27)	2.37(1.10)	1.542
Water	Vertical	3.04(1.48)	3.03(1.18)	0.049	3.33(1.26)	3.20(1.23)	0.583
	Horizontal	3.04(1.43)	2.74(1.15)	1.019	3.11(1.27)	2.82(1.14)	1.336
Image	Vertical	3.43(1.03)	3.34(0.87)	0.426	3.57(1.21)	3.22(1.04)	1.743
	Horizontal	2.80(1.09)	2.46(1.01)	1.467	3.09(1.05)	2.29(1.10)	4.032 ***
Shape & Form	Vertical	3.48(1.22)	3.89(0.87)	−1.674	3.89(0.96)	3.86(1.07)	0.145
	Horizontal	3.70(1.17)	3.34(1.06)	1.401	3.31(1.21)	3.28(1.26)	0.167
Material	Vertical	3.63(1.24)	3.51(1.01)	0.452	3.65(1.05)	3.26(1.05)	2.001 *
	Horizontal	3.46(1.19)	3.83(0.79)	−1.605	3.48(1.14)	3.58(1.09)	−0.503
Total		3.34(1.23)	3.30(1.02)	-	3.40(1.14)	3.20(1.09)	-

Note. * p < 0.05, *** p < 0.001, BDA *: Biophilic Design Attribute.

presents the differences in average preference scores for biophilic design attributes in the stairwell, categorized by gender and the presence or absence of depression. Among males, those with depression reported slightly higher preference scores (3.40) compared to their non-depressed counterparts (3.34). Conversely, females without depression showed higher preference scores (3.30) than those with depression (3.20), suggesting a divergence in how depressive symptoms influence spatial preferences by gender.

Among the non-depressed males, the attributes with above-average preferences included ‘Weather & View—Horizontal (4.09)’, ‘Shape & Form—Horizontal’, and ‘Material—Vertical’. The non-depressed females showed the strongest preferences for ‘Weather & View—Horizontal (3.91)’, ‘Shape & Form—Vertical’, and ‘Material—Horizontal’. In the group with depression, the males most preferred ‘Shape & Form—Vertical (3.89)’, followed by ‘Weather & View—Horizontal’ and ‘Material—Vertical’. For the females with depression, the most favored attributes were ‘Weather & View—Horizontal (4.08)’, ‘Shape & Form—Vertical’, and ‘Material—Horizontal’. Detailed rankings for each group are available in Table 13.

Paired sample t-tests were conducted to assess statistical differences between genders. No significant gender differences were found among the non-depressed participants. However, within the group experiencing depression, significant gender-based differences were observed in ‘Image—Horizontal (p < 0.001)’ and ‘Material—Vertical (p < 0.05)’. These findings suggest that under depressive conditions, females and males may differ more distinctly in how they perceive and prefer certain biophilic design elements, particularly those related to visual imagery and tactile materials.

In summary, the preferences for biophilic attributes in stairwells vary according to both gender and the presence of depressive symptoms. While ‘Weather & View—Horizontal’ consistently received high ratings across all groups, significant gender-based perceptual differences emerged specifically among those with depression, highlighting the nuanced role of psychological state in spatial preference formation.

Table 14. Average difference in preferences for biophilic design by gender in central hall spaces according to depression status.

Preference Survey Items		Normal			Depression
BDA *	Application Characteristics	Male (n = 46)	Female (n = 35)	t	Male (n = 54)	Female (n = 65)	t
		M(SD)	M(SD)		M(SD)	M(SD)
Weather & View	Vertical	3.93(0.88)	3.91(0.70)	0.113	3.91(0.76)	3.95(0.82)	−0.318
	Horizontal	3.76(1.18)	3.80(0.93)	−0.162	3.69(0.99)	3.71(0.95)	−0.127
Type of Plant & Landscape	Vertical	2.87(1.29)	2.86(1.26)	0.043	3.17(1.24)	2.74(1.16)	1.940
	Horizontal	3.26(1.16)	3.69(1.08)	−1.680	3.52(1.08)	3.74(0.91)	−1.210
Water	Vertical	3.13(1.48)	3.17(1.18)	−0.134	3.39(1.38)	2.98(1.34)	1.617
	Horizontal	2.87(1.22)	2.86(1.09)	0.047	3.20(1.22)	3.02(1.15)	0.865
Image	Vertical	2.46(1.09)	2.14(1.00)	1.327	2.89(1.11)	2.14(1.14)	3.610 ***
	Horizontal	2.63(1.22)	2.40(1.09)	0.882	2.93(1.15)	2.66(1.20)	1.219
Shape & Form	Vertical	3.39(1.11)	3.37(1.29)	0.075	3.46(1.09)	3.63(1.11)	−0.826
	Horizontal	3.04(1.17)	2.83(1.15)	0.824	3.37(1.15)	2.94(1.29)	1.911
Material	Vertical	3.48(1.22)	3.57(0.88)	−0.381	3.50(0.99)	3.71(0.96)	−1.158
	Horizontal	3.72(1.07)	3.71(0.83)	0.014	3.72(0.98)	3.52(1.12)	1.022
Total		3.21(1.17)	3.19(1.04)	-	3.39(1.10)	3.23(1.10)	-

Note. *** p < 0.001, BDA *: Biophilic Design Attribute.

presents the differences in average preference scores for biophilic design attributes in the central hall between genders according to the presence or absence of depression. The average preference scores of males and females without depression were 3.21 and 3.19, respectively, whereas those of males and females with depression were higher, at 3.39 and 3.23, respectively, indicating a stronger preference for biophilic design among participants with depressive symptoms. For males without depression, the attributes that showed preference levels above the average (3.21) were, in order, as follows: ‘Weather & View—Vertical (3.93)’, ‘Weather & View—Horizontal (3.76)’, ‘Material—Horizontal (3.72)’, ‘Material—Vertical (3.48)’, ‘Shape & Form—Vertical (3.39)’, and ‘Type of Plant & Landscape—Horizontal (3.26)’, while for females, the attributes that showed preference levels above the average (3.19) were ‘Weather & View—Vertical (3.91)’, ‘Weather & View—Horizontal (3.80)’, ‘Material—Horizontal (3.71)’, ‘Type of Plant & Landscape—Horizontal (3.69)’, ‘Material—Vertical (3.57)’, and ‘Shape & Form—Vertical (3.37)’, indicating higher levels of preference. Among males with depression, the attributes that exceeded the average score of 3.39 were, in order, as follows: ‘Weather & View—Vertical (3.91)’, ‘Material—Horizontal (3.72)’, ‘Weather & View—Horizontal (3.69)’, ‘Type of Plant & Landscape—Horizontal (3.52)’, ‘Material—Vertical (3.50)’, and ‘Shape & Form—Vertical (3.46)’, while females with depression, with an average of 3.23, showed higher preferences for ‘Weather & View—Vertical (3.95)’, ‘Type of Plant & Landscape—Horizontal (3.74)’, ‘Weather & View—Horizontal (3.71)’, ‘Material—Vertical (3.71)’, ‘Shape & Form—Vertical (3.63)’, and ‘Material—Horizontal (3.52)’. As with the stairwell, the t-test results for gender-based differences in biophilic design preferences according to the presence or absence of depression in the central hall showed no statistically significant differences between males and females without depression, whereas among those with depression, a significant difference was found in ‘Image—Vertical’ at the p < 0.001 level.

4.4. Preferences for Biophilic Design Attributes According to Depression Levels

Table 15. Biophilic design preferences in the corridor space by depression level: paired sample t-test results.

Preference Survey Items		Normal (n = 81)		Depression Level
BDA *	Application Characteristics			Mild (n = 47)		Moderate (n = 17)		Severe (n = 55)
		M(SD)	t	M(SD)	t	M(SD)	t	M(SD)	t
Weather & View	Vertical	3.65(0.98)	0.257	3.47(0.93)	−1.794	3.35(1.06)	−0.753	3.65(0.89)	0.381
	Horizontal	3.62(1.02)		3.74(1.07)		3.65(1.17)		3.60(1.05)
Type of Plant & Landscape	Vertical	2.67(1.29)	−1.485	2.85(1.16)	−1.030	2.53(1.12)	−0.677	2.76(1.02)	−2.481 *
	Horizontal	2.79(1.34)		2.98(1.17)		2.71(1.16)		3.16(1.13)
Water	Vertical	3.57(1.16)	5.160 ***	3.81(1.14)	4.955 ***	3.35(1.17)	0.824	3.36(1.30)	−0.331
	Horizontal	2.83(1.35)		2.98(1.09)		3.18(1.33)		3.42(1.10)
Image	Vertical	3.07(0.98)	3.940 ***	3.36(1.22)	2.921 **	2.76(1.03)	1.562	3.07(1.12)	1.932
	Horizontal	2.56(1.14)		2.83(1.27)		2.41(1.06)		2.78(1.24)
Shape & Form	Vertical	3.15(1.13)	0.716	3.30(0.95)	3.149 **	3.47(1.07)	0.000	3.15(1.22)	2.099 *
	Horizontal	3.05(1.15)		2.77(1.24)		3.47(1.01)		2.80(1.15)
Material	Vertical	3.67(1.06)	2.999 **	3.77(1.03)	0.829	3.65(0.86)	1.000	3.49(1.14)	1.252
	Horizontal	3.26(1.13)		3.64(1.07)		3.41(1.18)		3.25(1.24)
Total		3.16(1.14)	-	3.29(1.11)	-	3.16(1.10)	-	3.21(1.13)	-

Note. * p < 0.05, ** p < 0.01, *** p < 0.001, bold = biophilic design attributes with significantly higher preference, BDA *: Biophilic Design Attribute.

presents the results of average preference scores and paired sample t-tests for biophilic design attributes in corridor, classified by depression severity level. Among males, those with depression reported slightly higher preference scores (3.40) than their non-depressed counterparts (3.34). In contrast, non-depressed females exhibited higher preference scores (3.30) compared to females with depression (3.20), suggesting that the impact of depressive symptoms on spatial preferences may differ by gender.

For non-depressed males, the attributes rated above the group average included ‘Weather & View—Horizontal (4.09)’, ‘Shape & Form—Horizontal’, and ‘Material—Vertical’. Among the non-depressed, the most preferred attributes were ‘Weather & View—Horizontal (3.91)’, ‘Shape & Form—Vertical’, and ‘Material—Horizontal’. In the depressed group, males most strongly favored ‘Shape & Form—Vertical (3.89)’, followed by ‘Weather & View—Horizontal’ and ‘Material—Vertical’, while females showed the highest preferences for ‘Weather & View—Horizontal (4.08)’, ‘Shape & Form—Vertical’, and ‘Material—Horizontal’. Full rankings are provided in Table 15.

The paired sample t-tests revealed no statistically significant gender differences among the non-depressed participants. However, within the depression group, significant differences between males and females were observed for ‘Image—Horizontal (p < 0.001)’ and ‘Material—Vertical (p < 0.05)’. These results suggest that depressive symptoms may amplify gender-based differences in the perception of visual and tactile design elements.

To sum up, preference for biophilic design attributes in corridors varies depending on both gender and the presence of depressive symptoms. Notably, Weather & View—Horizontal emerged as a consistently preferred attribute across all subgroups. However, gender-specific perceptual differences—particularly in imagery and material-related features—were more pronounced under depressive conditions, underscoring the importance of mental health-informed design strategies in educational environments.

Table 16. Biophilic design preferences in stairwell space by depression level: paired sample t-test results.

Preference Survey Items		Normal (n = 81)		Depression Level
BDA *	Application Characteristics			Mild (n = 47)		Moderate (n = 17)		Severe (n = 55)
		M(SD)	t	M(SD)	t	M(SD)	t	M(SD)	t
Weather & View	Vertical	3.51(1.01)	−3.846 ***	3.45(1.00)	−4.644 ***	3.35(0.86)	−1.852	3.31(0.96)	−3.422 **
	Horizontal	4.01(1.08)		4.09(0.93)		3.88(0.99)		3.82(1.07)
Type of Plant & Landscape	Vertical	3.32(1.34)	5.285 ***	3.38(1.15)	4.371 ***	2.94(1.09)	3.347 **	3.33(1.17)	4.575 ***
	Horizontal	2.62(1.24)		2.53(1.25)		2.12(0.99)		2.64(1.18)
Water	Vertical	3.04(1.35)	1.134	3.49(1.23)	2.856 **	3.00(1.37)	0.270	3.15(1.19)	1.759
	Horizontal	2.91(1.32)		3.09(1.33)		2.94(1.14)		2.84(1.12)
Image	Vertical	3.40(0.96)	6.232 ***	3.45(1.16)	4.852 ***	3.24(1.15)	2.985 **	3.36(1.11)	4.666 ***
	Horizontal	2.65(1.06)		2.70(1.21)		2.35(1.22)		2.71(1.07)
Shape & Form	Vertical	3.65(1.10)	0.778	3.68(1.02)	2.733 **	4.12(0.78)	4.386 ***	3.96(1.07)	2.889 **
	Horizontal	3.54(1.13)		3.28(1.28)		2.76(1.03)		3.47(1.21)
Material	Vertical	3.58(1.14)	−0.283	3.66(1.03)	−0.904	3.41(1.00)	0.000	3.25(1.09)	−0.444
	Horizontal	3.62(1.04)		3.83(1.09)		3.41(1.12)		3.33(1.09)
Total		3.32(1.15)	-	3.39(1.14)	-	3.13(0.89)	-	3.26(1.11)	-

Note. ** p < 0.01, *** p < 0.001, bold = biophilic design attributes with significantly higher preference, BDA *: Biophilic Design Attribute.

presents the results of the average preference scores and paired sample t-tests for biophilic design attributes in stairwells, classified by depression severity level. The analysis revealed that the Mild group exhibited the highest overall preference (M = 3.39), followed by the Normal (3.32), Severe (3.26), and Moderate (3.13) groups.

In terms of specific attribute preferences, the Normal group reported the highest scores for ‘Weather & View—Horizontal (4.01)’, ‘Shape & Form—Vertical (3.65)’, and ‘Material—Horizontal (3.62)’. Similarly, the Mild group showed strong preferences for ‘Weather & View—Horizontal (4.09)’, ‘Material—Horizontal (3.83)’, and ‘Shape & Form—Vertical (3.68)’. Interestingly, the Moderate group prioritized ‘Shape & Form—Vertical (4.12)’, ‘Weather & View—Horizontal (3.88)’, and both ‘Material—Vertical’ and ‘Material—Horizontal (3.41 each)’. The Severe group preferred ‘Shape & Form—Vertical (3.96)’, ‘Weather & View—Horizontal (3.82)’, and ‘Shape & Form—Horizontal (3.47)’.

The results of the paired sample t-tests revealed statistically significant differences across all depression levels for two attributes: ‘Type of Plant & Landscape’ and ‘Image’. For ‘Type of Plant & Landscape’, vertical applications were favored by the Normal, Mild, and Moderate groups, whereas the Severe group preferred horizontal applications. In the case of Image, all the depression groups consistently showed higher preferences for vertical over horizontal applications.

Additional significant differences were identified by group: the Normal group showed a significant difference for ‘Weather & View’. The Mild group showed differences in ‘Weather & View’, ‘Water’, and ‘Shape & Form’. The Moderate group showed a significant difference for ‘Shape & Form’. The Severe group showed differences in ‘Weather & View’ and ‘Shape & Form’.

These findings suggest that while certain biophilic design attributes such as ‘Weather & View’ and ‘Shape & Form’ are valued across all depression levels, the manner of their application—particularly vertical versus horizontal orientation—may influence perceived effectiveness depending on the individual’s psychological state.

Table 17. Biophilic design preferences in the central hall space by depression level: paired sample t-test results.

Preference Survey Items		Normal (n = 81)		Depression Level
BDA *	Application Characteristics			Mild (n = 47)		Moderate (n = 17)		Severe (n = 55)
		M(SD)	t	M(SD)	t	M(SD)	t	M(SD)	t
Weather & View	Vertical	3.93(0.80)	1.180	4.00(0.78)	0.306	3.71(0.99)	1.305	3.95(0.73)	2.206 *
	Horizontal	3.78(1.07)		3.96(0.75)		3.35(0.86)		3.58(1.10)
Type of Plant & Landscape	Vertical	2.86(1.27)	−4.931 ***	2.89(1.22)	−3.971 ***	2.41(1.06)	−3.405 **	3.13(1.22)	−3.107 **
	Horizontal	3.44(1.14)		3.66(0.98)		3.59(0.94)		3.64(1.02)
Water	Vertical	3.15(1.35)	2.136 *	3.23(1.35)	0.850	2.47(1.37)	−1.692	3.33(1.33)	0.866
	Horizontal	2.86(1.16)		3.06(1.22)		2.88(1.32)		3.20(1.11)
Image	Vertical	2.32(1.06)	−1.872	2.40(1.15)	−2.277 *	2.24(1.15)	−1.000	2.62(1.22)	−1.375
	Horizontal	2.53(1.16)		2.83(1.13)		2.53(1.18)		2.82(1.23)
Shape & Form	Vertical	3.38(1.18)	2.860 **	3.53(1.08)	2.469 *	3.24(1.03)	0.427	3.67(1.14)	2.560 *
	Horizontal	2.95(1.16)		3.06(1.22)		3.06(1.25)		3.22(1.27)
Material	Vertical	3.52(1.09)	−1.650	3.87(0.80)	0.711	3.53(0.87)	0.382	3.42(1.10)	−0.817
	Horizontal	3.72(0.96)		3.77(1.05)		3.41(1.06)		3.55(1.07)
Total		3.20(1.12)	-	3.36(1.06)	-	3.04(1.09)	-	3.34(1.13)	-

Note. * p < 0.05, ** p < 0.01, *** p < 0.001, bold = biophilic design attributes with significantly higher preference, BDA *: Biophilic Design Attribute.

summarizes the results of the preference ratings and paired sample t-tests for biophilic design attributes in the central hall, categorized by levels of depression. The Mild group showed the highest overall preference (M = 3.36), followed by the Severe (M = 3.34), Normal (M = 3.20), and Moderate groups (M = 3.04).

Preference patterns varied by group. The Normal group reported high preference for ‘Weather & View—Vertical (3.93)’, ‘Weather & View—Horizontal (3.78)’, and ‘Material—Horizontal (3.72)’. The Mild group favored ‘Weather & View—Vertical (4.00)’, ‘Weather & View—Horizontal (3.96)’, and ‘Material—Vertical (3.87)’. The Moderate group preferred ‘Weather & View—Vertical (3.71)’, ‘Type of Plant & Landscape—Horizontal (3.59)’, and ‘Material—Vertical (3.53)’. The Severe group showed high preference for ‘Weather & View—Vertical (3.95)’, ‘Shape & Form—Vertical (3.67)’, and ‘Type of Plant & Landscape—Horizontal (3.64)’.

The statistical analysis revealed that ‘Type of Plant & Landscape’ showed significant differences across all depression levels, with a general preference for horizontal application. Additional significant differences were observed in ‘Water’ and ‘Shape & Form’ for the Normal group, ‘Image’ and ‘Shape & Form’ for the Mild group, and ‘Weather & View’ and ‘Shape & Form’ for the Severe group. These results indicate that sensitivity to specific biophilic attributes differs by psychological state, highlighting the potential of adaptive design strategies in mental health-supportive environments.

5. Discussion

The results of the analysis of this study are as shown in Figure 2 and can be summarized as follows:

First, the adolescents demonstrated a consistently higher preference for biophilic design images compared to those of conventional school common areas. Among the various attributes, ‘Weather & View’ received the highest preference across all spatial types. For example, ‘Weather & View—Horizontal’ in stairwells scored 3.97 (p < 0.001), and in central halls, ‘Weather & View—Vertical’ and ‘Horizontal’ scored 3.93 (p < 0.05) and 3.73 (p < 0.01), respectively. In corridors, ‘Material—Vertical’ scored 3.64 (p < 0.01). Notably, horizontal applications were preferred in corridors and stairwells, whereas vertical applications were favored in central halls, reflecting the influence of spatial function and openness on perceptual response. This implies the importance of incorporating architectural elements such as windows, atriums, and courtyards to modulate degrees of visual access to nature. Statistically significant differences were identified across all common areas for ‘Type of Plant & Landscape’, ‘Image’, and ‘Shape & Form’. Additionally, application orientation significantly influenced preference in ‘Water’ and ‘Material’ (corridor), ‘Weather & View’ and ‘Water’ (stairwell), and ‘Weather & View’ (central hall), suggesting that the application method must be tailored to spatial function.

Second, analysis by gender and depression status revealed that adolescents with depression consistently showed higher preference levels across all space types. This finding aligns with prior research highlighting the therapeutic potential of biophilic environments for psychological recovery [68,69]. In corridors, gender differences were particularly evident in ‘Weather & View—Vertical’, ‘Weather & View—Horizontal’, and ‘Material—Vertical’. In stairwells, ‘Weather & View—Horizontal’ was the most preferred attribute regardless of gender or depression status. In central halls, while high preference was shown for vertical applications of ‘Weather & View’ and ‘Material’, a significant gender difference was found only for ‘Image—Vertical’ among depressed adolescents (p < 0.001). These results emphasize the need for biophilic design strategies that are sensitive to both gender and mental health variations.

Third, when analyzed by depression level, the adolescents with mild depression reported the highest overall preference scores, followed by those with severe symptoms. This indicates a greater emotional receptiveness to nature-based stimuli among those with mild depressive symptoms. For example, the Mild group showed the highest preference for ‘Water—Vertical’ in corridors (3.81, p < 0.001), the Moderate group preferred ‘Shape & Form—Vertical’ in stairwells (4.12, p < 0.001), and the Severe group showed high preference for ‘Weather & View—Vertical’ in central halls (3.95, p < 0.05). Across all depression levels, corridors consistently showed high preference for ‘Weather & View’ and ‘Material’, particularly in vertical formats. Preferences for sensory-rich features such as ‘Water’, ‘Image’, and ‘Shape & Form’ were also elevated, underscoring the restorative potential of biophilic elements [63]. The strong preference for vertical applications further suggests that cognitive stimulation and spatial framing may have a greater emotional impact than direct accessibility [70,71].

By application characteristics, significant differences were observed for ‘Water’, ‘Image’, ‘Shape & Form’, and ‘Material’ in the Normal and Mild groups, with a consistent tendency to prefer vertical applications. In stairwells, horizontal ‘Weather & View’ was preferred across all groups, while vertical ‘Shape & Form’ gained preference among adolescents with moderate and severe depression. In the central hall, vertical ‘Weather & View’ was again the most preferred across all levels, and the horizontal application of ‘Type of Plant & Landscape’ showed significant differences. Group-specific significant attributes included ‘Water’ (Normal), ‘Image’ (Mild), and ‘Weather & View’, and ‘Shape & Form’ (Severe).

In conclusion, these findings demonstrate that adolescents’ preferences for biophilic design attributes are differentiated by both space type and psychological condition. Notably, those with mild and severe depression exhibited heightened responses to sensory-rich and nature-based elements, affirming the need for targeted biophilic interventions. Future school design should thus adopt a more nuanced and responsive approach—considering depression levels, gender differences, and space-specific functions—to optimize environmental support for adolescent mental health.

6. Conclusions

6.1. Key Findings and Implications

This study investigated the relationship between adolescents’ depression levels and their preferences for biophilic design attributes applied to school common areas, aiming to establish evidence-based spatial design strategies for emotionally supportive educational environments. The significance of the research lies in demonstrating that biophilic design, when aligned with adolescents’ psychological characteristics, can play a critical role in enhancing mental well-being during a developmentally vulnerable stage.

First, images incorporating biophilic design elements were consistently rated higher than those of conventional school environments. Among all spatial types, the ‘Weather & View’ attribute received the highest preference scores, with horizontal applications favored in corridors and stairwells and vertical applications preferred in central halls. These findings highlight the importance of aligning the spatial deployment of biophilic elements with the function and visual openness of each common area.

Second, the adolescents diagnosed with depression consistently exhibited higher preferences for biophilic design elements compared to their non-depressed peers across all spaces. This supports existing evidence on the psychological benefits of nature exposure and underscores the therapeutic potential of biophilic design in school settings. A statistically significant gender difference (p < 0.001) was identified for the ‘Image—Vertical’ attribute in the central hall, suggesting that gender-based perceptual differences should also inform biophilic design approaches.

Third, the adolescents with mild depression showed the highest overall preference scores, particularly for sensory-driven attributes such as ‘Water’, ‘Shape & Form’, ‘Image’, and ‘Material’. Notably, preference varied with application direction (vertical vs. horizontal), indicating that environmental sensitivity is modulated by the severity of depressive symptoms. These results suggest that vertical elements—associated with visual structure and cognitive stimulation—may be especially effective in supporting emotional regulation.

These findings yield several important implications for biophilic design in school environments. First, the variation in preference by space type and application orientation calls for differentiated spatial strategies that reflect the function and perceptual context of each area. Second, the strong positive responses from adolescents with depression highlight the potential of biophilic design as a preventive and therapeutic tool for supporting mental health. Third, gender-specific perceptual patterns suggest that design approaches should be inclusive of gendered responses to environmental stimuli. Lastly, the high preference for sensory and cognitively engaging attributes implies that such features may offer more restorative value than mere visual access to nature.

Unlike prior case-oriented approaches, this study visualized biophilic attributes and empirically analyzed user preferences based on psychological state and gender, allowing the proposal of differentiated design strategies for each type of school common area. This contributes to the growing body of knowledge supporting targeted, mental health-sensitive design interventions.

However, while the elevated preferences among adolescents with depressive symptoms may reflect increased emotional receptivity to nature-based environments, it is important to recognize that preference alone does not imply therapeutic efficacy. As emphasized in environmental psychology literature, aesthetic or perceptual appeal may not directly correspond to psychological restoration or clinical outcomes [72,73]. Preference often reflects immediate visual attraction rather than deeper emotional or cognitive recovery, as suggested by Kaplan and Kaplan [74]. Therefore, although the findings indicate promising affective responses, future research should empirically verify the psychological and physiological effects of biophilic design using behavioral observations, biometric indicators, or longitudinal intervention studies.

6.2. Limitation and Future Research

This study has a few limitations. First, it was conducted with a geographically and culturally homogeneous sample of Korean adolescents, which limits the generalizability of the findings across different cultural contexts. Cultural background has been shown to influence how individuals perceive and emotionally respond to natural environments, including the interpretation of biophilic elements [75,76]. For example, preferences for spatial openness, vegetation types, or symbolic representations of nature may differ based on cultural norms and environmental familiarity. Therefore, future research should conduct cross-cultural comparative studies to examine whether the affective responses and design preferences observed in this study hold across diverse adolescent populations. Such efforts will enhance the cultural applicability and global relevance of biophilic design strategies in educational environments.

Second, while the CES-DC is a validated and widely used instrument, its cutoff scores were not culturally calibrated for Korean adolescents, which may affect the accuracy of depression level classification. Future research should pursue localized clinical validation to enhance diagnostic relevance.

Third, the cross-sectional design restricts causal inference and does not permit conclusions regarding therapeutic effects. Although the elevated preferences observed among adolescents with depressive symptoms suggest emotional receptivity to nature-based environments, these findings should not be interpreted as evidence of clinical improvement. To verify the mental health benefits of biophilic design, future studies should adopt longitudinal or experimental approaches and incorporate contextual and behavioral investigations in real school settings. Expanding the scope of analysis to include variables such as stress coping mechanisms, environmental awareness, and spatial behavior will further strengthen the framework for adolescent-centered biophilic design.

In addition, although biophilic design preferences were analyzed using multiple paired sample t-tests, no formal correction for multiple comparisons was applied. This decision was made to preserve statistical power in line with the exploratory purpose of the study. Furthermore, while gender and age were considered through stratified sampling and subgroup comparisons, potential confounding variables were not statistically controlled using multivariate techniques. Future studies are encouraged to apply regression analysis or ANCOVA to more clearly isolate the effects of demographic factors.

Lastly, while the findings offer meaningful insights into adolescents’ affective responses to biophilic features, visual preference alone does not imply therapeutic efficacy. As the environmental psychology literature suggests, subjective preferences may not directly correlate with psychological or physiological outcomes. This study thus acknowledges the limitations of relying solely on perceptual data and recommends future research to incorporate empirical validation—such as behavioral tracking, biometric measures, and longitudinal interventions—to assess the actual impact of biophilic design on adolescent mental health.