Impact of office light environment on mental health interventions for employees: An investigative analysis

Abstract

Background

The increasing prevalence of work-related stress and mental health issues has become a global concern, particularly in developing countries. The light environment in office spaces, known to influence both visual and non-visual aspects of health, is a critical factor that needs further exploration for its potential in enhancing employees’ psychological well-being.

Objective

The aim of our study was to investigate the role of light environments in office spaces in influencing the psychological well-being of employees.

Methods

The study was conducted in 2 office locations in Shanghai and Dalian, China and analyzed data from 235 employees. Data on the effects of the light environment were self-reported by the participants, and the psychological well-being of the employees was measured on 2 dimensions (differences in color perception, and differences in perception between natural dynamic lighting and artificial static lighting). The effects of hue and lightness on employee psychology, and the effects of natural versus conventional static lighting on employee mood were analyzed.

Results

The findings revealed that the hue and luminance of office spaces significantly affect employees’ psychological satisfaction and emotional states. Specifically, natural dynamic lighting, which aligns with the natural photoperiod, was found to effectively reduce negative emotions such as anger and depression, offering a promising intervention for improving mental health in the workplace.

Conclusions

The light environment in office settings plays a significant role in mitigating mental health issues among employees. While the study confirms the positive effects of dynamic lighting on mental health, it also highlights the need for further interdisciplinary research to fully understand the complex mechanisms involved.

Keywords

workplace healthy light environments human factors analysis proactive interventions employee mental health health and well-being

Introduction

Along with the accelerated pace of work and life, the mental health status of the working population, especially depression and anxiety disorders, has attracted widespread social concern. Helen Frankish has stated in the medical journal The Lancet that the growing number of psychiatric disorders will lead to a global health crisis¹; and the author urgently calls for action to expand services for populations with mental health problems, especially for low- and middle-income income countries and to promote global mental health initiatives.

Light has a profound effect on our physical and mental health.^2,3 In addition to its basic function of illumination, light also harbors therapeutic and healing-promoting properties. The spectral composition and light intensity of light sources have a significant impact on people's daily lives. Some studies have confirmed that improving indoor lighting conditions in the workplace has the potential to contribute to proper circadian hormonal rhythms, sleep and health.^4,5 An optimized lighting environment not only enhances the comfort and safety of an indoor space, but also exhibits many positive characteristics. Dynamic lighting refers to a lighting strategy where the intensity and/or spectral composition of indoor light is varied over time according to preset settings. This variation is designed to alter the activation state of one or more photoreceptor over an extended period, typically throughout a significant portion of the day. Such a lighting system holds promise for addressing the chronobiological and psychological needs of individuals at specific times or during specific activities. Of particular note, several studies^6,7 have explored the positive effects of dynamic lighting on individual health and well-being. A study on office environments⁸ showed that exposure to dynamic light had significant benefits on subjective sleepiness, positive mood and task performance.

Numerous studies have pointed out^9–12 that the work environment is one of the key factors affecting employee performance, productivity, and overall well-being. An industrial study¹³ showed that good lighting conditions can improve employee productivity and concentration. Suitable indoor lighting is a prerequisite for optimizing visual performance, visual comfort and the comfort of the working environment, and the positive effects of adequate lighting can be further extended.⁹ However, despite a deeper scientific understanding of the effects of light on biological mechanisms, lighting design in built environments still focuses primarily on meeting the needs of visual performance. That is, in office lighting design, the focus has often been on providing “suitable and sufficient” light to accomplish tasks and minimize visual discomfort. As architects and engineering designers are increasingly encouraged to create environments that promote human health and well-being, new demands are being placed on indoor light environments.¹⁴

The purpose of this study is to sort out and analyze the correlation between indoor light environment in office space and human health using objective human factors data analysis, and to show whether light environment can be classified as one of the main factors affecting employees’ physical and mental health. By analyzing objective human factors data on the effects of light environment on employees’ physical and mental health and work efficiency through both visual and non-visual channels, the role of light environment in influencing employees’ physical and mental health can be explained more accurately.

The research question has the following 2 questions:

Impact of Indoor Light Environment on Mental Health

Research Question: How does the indoor light environment in office spaces influence the mental health of employees? Can this environment be considered a significant determinant of their psychological well-being?

Definition: The indoor light environment encompasses the type of lighting (natural vs. artificial), level of illumination (measured in lux), and color temperature (measured in Kelvin). Mental health outcomes will be quantitatively assessed using the Brunel Mood Scale, which evaluates key emotional states such as anger, confusion, depression, fatigue, tension, and vigor. b.

Impact of Office Lighting on Physical Health

Research Question: What is the impact of the indoor light environment in office spaces on the physical health of employees, and how is this impact manifested?

Definition: Office lighting, defined by the type of lighting, level of illumination, and color temperature, will be the independent variable. Physical health will be measured through physiological indicators including blood pressure, pulse rate, body temperature, and heart rate. These will be objectively monitored using a wrist blood pressure monitor, a non-contact thermometer, and a smart bracelet.

Overview of the study

In order to test the intervention effect of indoor light environment in office space on staff's mental health, we conducted experiments and data summary analysis. As shown in Figure 1, the light environment of office space mainly affects the physical and mental health and work efficiency of employees through visual and non-visual pathways. As far as the current practice of light environment in office space is concerned, on the basis of safeguarding visual health, different office spaces show different health orientations and ways of creating light environments, so we have conducted investigations and studies in 2 representative office spaces in Shanghai and Dalian, China, namely, Case A (experiments on the differences in color perception) and Case B (experiments on the differences in the perceptions of natural dynamic lighting and artificial static lighting). Their basic information is shown in Table 1, where we identified participants from a list provided by facility management and invited them to participate via email. The email included a description of the study and a link to the online survey. Participants gave their consent by completing the online survey. It is important to state that the respondents in this experiment were informed about the experiment and were willing to participate.

Figure 1.

The relationship between light environment and staff health and productivity.

Table 1.

Basic information of the cases.

	Test site	Space size	Number of staff	Type of space
Case Study A	Shanghai	1680m²	232	Open plan office space
Case Study B	Dalian	940m²	96	Open plan office space

Tests for emotional health: experiments on color perception differences

Participants

In Case A, our recruitment process initially involved 232 employees. From this group, 200 participants (111 males and 89 females) were deemed eligible for inclusion in the experimental phase of the study. This cohort exhibited a diverse age range, spanning from 21 to 57 years. By way of self-report, we were informed that all participants had visual acuity or corrected visual acuity of 1.0 or better, and that none had colour blindness or colour deficiency.

Methods

The survey design was formulated based on an analysis of spatial requirements, structured through a logical framework. Data on color schemes and brightness preferences were collected via a combination of fieldwork, in-depth interviews, online experiments, and offline surveys. The following elaborates on the terminology and experimental approach:

Spatial Brightness and Color Preference

Spatial Brightness: This refers to the perceived intensity and distribution of light within the workspace.

Color Preference: This denotes individual selections and inclinations towards specific colors within the office setting. It is important to stress that we are talking about the colour of light here, not the colour of paint, as they are perceived differently. b.

Color Information and Standardization

Data Collection: Color information was primarily gathered using color cards, which allowed participants to indicate their preferences. These preferences were then cross-referenced with the TM-30 international color hue scale to ensure standardization across the study.

Weighted Data: The weighted data reflected the relative importance of each color within the overall color scheme, based on participant selection frequency.

Two separate experiments were conducted to assess spatial brightness and color preference. A set of color schemes was developed based on experimental data, which was then evaluated through a satisfaction survey. The same participant group was involved in both experiments. c.

Luminance Preferences

Methodology: Initially, luminance preferences were gauged using cards that represented different luminance levels. These were later correlated with actual luminance measurements in the office environment to validate the findings. Specifically, we control changes in the brightness of the lighting environment by adjusting the brightness of the LED strips in the office to meet the preferences of the staff.

Color on Paper vs. Color in Lighting

Medium Discrepancy: We acknowledge the inherent differences between color on paper and color in lighting. The color cards were employed as a preliminary tool to gauge preferences. These preferences were then cross-verified against actual lighting conditions, with office lighting adjusted to replicate the card colors as accurately as possible.

The experimental method involved using a set of 12 color cards, ranging from red to purple. Participants evaluated these colors using the Brunel State of Mind Scale, employing a five-point Likert scale (0 to 4). Extreme ratings were excluded to reduce their influence, and the average score was calculated from the remaining data. Similarly, luminance levels were categorized into 12 stages, and participants provided scores for emotional arousal.

Results

The study's findings suggest that the hue, brightness, and spatial orientation of color significantly influence employees’ psychological satisfaction and emotional intensity. As illustrated in Figure 2, key outcomes include:

Figure 2.

Quantitative analysis chart for hue, lightness and spatial tendency research.

Color tendency

Yellow and Green: These colors were associated with higher psychological satisfaction. Emotional activity decreased progressively from red to purple, with yellow offering a balance between high satisfaction and emotional activity, while green was associated with high satisfaction and lower emotional activity.

Luminance tendency

Light Gray and White: These luminance levels were favored for their ability to elicit higher psychological satisfaction, aligning with a preference for brighter colors. Emotional activity stabilized at medium gray before decreasing at darker luminance levels, indicating a parallel decline in psychological evaluation and emotional intensity as luminance diminished.

Tests for physical health: experiments on perceptual differences between natural dynamic lighting and artificial static lighting

Participants

We recruited 35 participants (17 males and 18 females), aged 20 to 52, all of whom held a bachelor's degree or higher. The participants engaged in both horizontal and vertical work modes and had resided in the local area for at least six months. All participants had normal or corrected visual acuity and were free from any other ocular diseases.

Methods

The experiment was conducted in two distinct office environments: one with natural dynamic lighting and the other with artificial static lighting. The experimental sessions took place from 8:00 AM to 5:00 PM, reflecting a typical workday. Each participant spent 20 min in the natural lighting space and 20 min in the static lighting space, performing paper-based office tasks and computer-based office work. During these sessions, participants completed a comprehensive visual comfort evaluation questionnaire. A 10-min rest period was provided between sessions, during which the experimental staff recorded the data. The overall experiment lasted approximately seven hours (four hours in the morning and three hours in the afternoon), with measurements taken hourly, totaling seven measurements throughout the day.

Intervention

Participants were exposed to each work environment for 20-min intervals. In the natural dynamic lighting environment, participants performed typical office tasks such as writing, reading, and organizing documents, as well as computer-based work. The lighting conditions were as follows:

Natural Dynamic Lighting: This environment was equipped with windows allowing natural light to enter throughout the day. Participants were seated approximately 1.5 to 3 metres from the window. The illumination (measured in lux) and color temperature (CCT, measured in Kelvin) varied according to the time of day and weather conditions. The dynamic lighting automatically adjusted in response to these environmental changes.

Artificial Static Lighting: The static lighting environment was a closed room with fixed lighting fixtures that maintained constant illumination and CCT throughout the experiment. The illumination intensity under static artificial lighting conditions is 400 Lux and the colour temperature is 4000 K.

Data collection

Data collection comprised both subjective evaluations and physiological measurements:

Subjective Evaluations: Participants’ psychological states were assessed using the Brunel Mood Scale, which utilizes a five-point Likert scale ranging from 0 (“not at all”) to 4 (“very much”). The scale includes 23 items spanning six dimensions: anger, confusion, depression, fatigue, tension, and vigor.

Physiological Measurements: Physiological parameters were recorded using the following instruments:

Blood Pressure and Pulse Rate: Measured with an OMRON wrist blood pressure monitor.

Body Temperature: Measured with a non-contact thermometer.

Heart Rate: Monitored using a smart bracelet.

Results

The findings indicated that the natural light cycle with dynamic lighting significantly reduced negative emotions, such as anger and depression, compared to the traditional static lighting environment. The dynamic lighting, which varied throughout the day in response to changes in weather and the sun's position, appeared to be more in harmony with the human body's natural circadian rhythm. Conversely, the static lighting environment had a pronounced stimulating effect, increasing levels of psychological activity Figure 3.

Figure 3.

The effect of natural light versus traditional static lighting on the subjective state of mind.

Discussion

This study determined that the experimental research was carried out from the color perception difference of employees, the perception difference between natural dynamic lighting and artificial static lighting at 2 levels. Utilizing strong instruments and analyses, including the Brunel State of Mind Scale and physiological measurements, we found that the light environment, characterized by type of lighting, illumination levels, and color temperature, significantly influences employee well-being. Our experiments on color perception and the comparison between natural dynamic lighting and artificial static lighting revealed that certain colors and lighting conditions can enhance psychological satisfaction and reduce negative emotions. The results underscore the importance of considering light environment as a main factor affecting employee health and suggest that dynamic lighting aligned with natural light cycles may be more beneficial for mental health. This study not only contributes to the understanding of the therapeutic potential of light in workplace design but also highlights the need for lighting solutions that promote human health and well-being, aligning with the emerging demands on indoor light environments.

The results of this study reflect the analysis of perceptual experience in space by office workers. Human perception has been an important theme in design research, and various types of research have emphasized the connection between perception and physical and mental activities, especially in terms of spatial experience.¹⁵ Essentially spatial perception is closely related to the body, which is not only a recipient of sensory stimuli, but also an active agent in interacting with the perceptible environment and assisting the senses in mediating the relationship between mind, body, and consciousness and space.¹⁵ With the emphasis on health and well-being, there has been a trend to design supportive environments to improve human health and well-being. And when spatial perception is involved in the design of healthy environments, it becomes a key element of research on environmental influences on well-being and health.¹⁶ In the twenty-first century, addressing the physical and mental health issues that result from fast-paced, high-intensity office patterns has become a central issue in promoting the health and well-being of all human beings. The World Health Organization (WHO) states that a safe and healthy work environment is essential, and that we need to invest in building a culture of prevention around mental health at work, reshaping the work environment to stop stigmatization and social exclusion, and ensuring that employees with mental health problems feel protected and supported,¹⁷ which has created a whole new set of requirements for research in the fields of architecture, management, and others. And within the design discourse, perception-led experience design for office spaces plays an integral and supportive role in building a culture of prevention for mental health.¹⁸

The results of existing studies suggest that work environment influences do have a certain impact on the mental health status of the working population,^19,20 especially the impact of poor work nature, work pressure and occupational stress, workplace interpersonal support and workplace health service provision on the mental health of the working population.^21,22 Therefore, in the workplace health promotion interventions, targeted to make improvements in this aspect of the poor working environment, indoor light environment and other support for human mental health to promote the physical and mental health of the working population. Targeted control and improvement of adverse work environment factors is conducive to improving the mental health of the occupational population.²³

Light and visual health. As a visual organ also has the function of capturing the wave characteristics of light, which is manifested in the discernment of coloration. High-quality light coloration quality can enhance people's comfort in the light environment, different spaces for the light coloration needs are not the same, of which the office is more suitable for the use of intermediate tones of the light environment. In addition, research has found that too much light, high-frequency flashing, glare, ghosting and other bad light environment, will not only lead to the reduction of visual performance, visual fatigue, but also reduce the efficiency of the work, affecting the progress of the situation²; in the long run under the role of the more will bring about serious visual injuries, such as nearsightedness, dry eye and so on.¹⁴

Physiological effects of light. The light environment has a significant effect on the physiological state, the dark environment stimulates the pineal gland of the human brain to synthetic and secretion of melatonin, while the bright environment leads to pupil constriction and inhibition of melatonin secretion.^24,25

The emotional effect of light. The visual image formed by the light environment and space as a constituent of the emotional system makes light indispensable in the human perception and emotional experience of the act of activity.²⁶ John Flynn, a pioneer in lighting psychology, confirmed that changes in the light environment cause people to respond differently to feelings of privacy, pleasure, relaxation, and so on.²⁷ Warm tones and high brightness coloration, more attractive to the attention, able to draw the visual sense of distance; and cool tones, low brightness coloration, easy to be ignored, easy to produce a sense of distance backward in the vision. For example, in a narrow space, the use of light environment design, with light blue as the tone, will give people a visual illusion, so that the space appears to be wider. In the working environment, the reasonable use of light environment can make the staff keep a good mood in the work.²⁸

Our experiments show that the light environment in the office space has a good intervention effect on the mental health of the staff in the space, and the perception-led office light environment creation plays an indispensable supportive role in building a preventive culture of mental health. How to guide through the visual level of perception, enhance the human emotional response in the psychological and physiological system, so that it is synergistic under the role of neural regulation of the human brain mechanism, enhance the human and the spatial environment to produce a better interactive experience. Our study further validates the role of spatial light environments on the mental health of staff member and enriches the interventions to alleviate the psychological stress of staff member.

Limitations

This study analyses the intervention of the light environment in architectural spaces on the health of the working population, which is conducive to the enhancement of the mental health of the occupational population. However, there are some limitations in the study: firstly, gender, age, income and family status are also used as influencing factors for individual mental health, and simply the function of proactive health intervention in the workspace is used as one of the influencing factors, which does not allow for a more comprehensive analysis of the influencing factors of the intervention on the mental health of the staff, which is a limitation of the study. Secondly, the impact of each workplace environment on the psychological condition of the occupational population is different, so that it cannot be a blanket statement, but requires specific analyses and “precision” health promotion. Finally, the initial use of matt or printed colour to represent lighter colour in the experiments was also inaccurate and needs to be analyzed more accurately in subsequent studies.

Conclusions

Current research suggests that stronger negative influences, stress exposure, and affective reactivity in daily work are all associated with increased depression among employees, and that alleviating work stress is an effective intervention on the way to reducing the risk of depression and improving mental health in office populations. Our findings reveal insights into the different dimensions of work stress relief, and this study adds to the potential approaches to intervene in the mental health of the working population from the dimensions of the light environment in a space. Analyzing the effects of the light environment in office space on employees’ mental health from two dimensions of experiments on Color Perception Differences and experiments on Perceptual Differences between Natural Dynamic Lighting and Artificial Static Lighting of artificial lighting not only expands the relevance of human health in the field of spatial environments, but also promotes interdisciplinary research. Therefore, in further research on work stress, we should grasp the interdisciplinary and multidisciplinary characteristics of work stress and establish a research system of mental health intervention for working people from multiple dimensions.

Footnotes

Acknowledgments

The author wishes to thank the anonymous referees who provided valuable comments on an earlier draft of this paper.

ORCID iD

Dian Jiao

Ethics approval

Not applicable.

Informed consent

Written informed consent was obtained from all the participants prior to the enrollment of this study.

Funding

The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by The National Social Science Fund of China (Grant numbers 21BSH039).

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

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