With further industrialization and modernization, increasing occupational psychological problems have gained attention from all social sectors. Indeed, occupational stress can lead to negative conditions such as exhaustion [1
] and depression [2
] and might seriously damage the occupational population’s work ability, social function and status of well-being [3
]. Meanwhile, depression has become one of the most common psychological disorders worldwide. The World Health Organization (WHO) ranked it as the fourth cause of disability, but predicted it to increase to second place by 2020. In China, depression has been ranked as the second highest burden of medical expenses [5
]. Now, the occupational population is the basis of social and economic development, and maintaining their safety and health is an important factor for social progress [6
]. Depression affects people’s ability to work, possibly leading to low production efficiency and even disability. In contrast, well-being is another important guarantee for their safe and efficient work. Thus, discovering the role of occupational stress in maintaining well-being and development of depression has been the focus in occupational health studies. Some studies have shown that occupational stress influences depression and well-being through various working conditions, i.e., effort-reward imbalance is closely associated with depression; job demands (e.g., high work pressure, emotional needs, role ambiguity) might lead to sleep disorders [7
], anhedonia [8
], and so on, which serve as the main component of depression. Well-being and protective factors, specifically, social support [9
], self-esteem [10
] and autonomy [11
] might alleviate occupational factors’ negative effects through increasing employee learning opportunities [12
] and improving a sense of integration in the work [14
At present, most research on this topic has been conducted on health hazards and thereby achieved great success [11
]. However, to predict and evaluate occupational stress and its outcomes, most studies are based on occupational stressors, or, in recent years [12
], they have used two internationally recognized models, i.e., the job demands-control (JDC) model [15
] and the effort-reward imbalance (ERI) model [16
]. These two models’ simple structure and content have become the greatest advantage for their application, and they have been widely used in the study of occupational stress for the past 30 years. However, this simplicity also results in prediction or evaluation bias for occupational stress and its outcomes. The models focus on two important parts of occupational stress that have been respectively taken as the theoretical basis of its prediction and evaluation. However, in the face of the occupational population’s growing complexity and occupational characteristics, these evaluation results might, to some extent, not reflect the current occupational population’s panorama of occupational stress [12
], leading to uncertain correlations with health outcomes. In other words, stress evaluation by JDC or ERI models alone might miss certain populations’ stressed status. For example, the ERI questionnaire cannot accurately assess psychological demands on visual display terminal operators, thus potentially drawing biassed conclusions on occupational stresses’ prevalence. Many works based on the two models have shown many inconsistent results, and job complexity leads, possibly, to producing one-sided evaluation results through application of the two single models [18
]. Also, many studies have questioned how systematic the two models actually are [20
For deeper understanding of the JDC and ERI, many studies have conducted research on occupational stress by using the JDC and ERI simultaneously to solve occupational stress problems under more comprehensive and systematic conditions. Obviously, however, one issue cannot be avoided even by using these two models simultaneously: their evaluation systems are independent. In addition, they were initially designed to evaluate occupational stress from independent angles, and confounding their dimensions or items without a theoretical basis is inadvisable. Although simultaneous JDC and ERI usage can measure stress factors from different perspectives, it is difficult to explain them according to one comprehensive index in a common framework, especially for laypeople. Thus, simultaneous usage maintains just the role of simultaneousness. To compensate for this drawback and for extensive research on occupational stress, we require development of a theoretical platform.
In fact, some scholars have already noticed the issue and made efforts to resolve it. In 2003, Bakker et al. [20
] proposed the “Job demand–resource model”. This model attempted reforms in the working condition of job demands and introduced “job resource” as the dimension interactive with “job demand”. Subsequent literature has shown this model’s practicability and applicability [12
]. As a model recently gaining more and more attention, the job demand-resource model also indicates that measurement of psychological working conditions needs to be comprehensive. Otherwise, it might lead to biassed assessment. However, after reviewing the literature regarding the demand-resource model, we have found that only some of the model’s scales/items are selected from occupational stress-related measurement tools, while items’ specificity to stress measurement remains to be discussed. At the same time, we found that various studies have selected different scales for establishing the demand-resource model’s framework, scales not even familiar in the study of occupational stress. In an article on the relationship between the job demand-resource model and burnout, Bakker himself also indicated that the model’s scales have been selected from heterogeneous scales without the assessment of their reliability and validity. Therefore, we believe that the demand-resource model might have disadvantages in the specificity of measuring occupational stress.
By considering these issues, and for developing a model that fits the Chinese social and cultural background, we propose the “job burden-capital model” on the basis of the widely used JDC and ERI in China for predicting and evaluating the occupational population’s health outcomes (depression and well-being). The model’s basic theory supposes that when the job burden-capital does not match, since the occupational population’s job burden goes beyond the capital owned, risk of depression increases. Additionally, regulation of personal characteristics affects the extent and speed of depression’s development.
“Job burden” mainly refers to those psychological, physical, organizational, social and personal job factors that require enhanced or transitory physical and/or psychological diathesis or capability and lead to daily costs physiologically and/or psychologically. For example, the work environment, task intensity, psychological burden, skill requirements and so on probably increase risk of depression. When the occupational staff’s available work capital is certain, high job burden might directly increase risk for and development of depression [21
]. It might also reduce their well-being and work efficiency [22
“Capital” refers to those psychological, physical, organizational, social and personal factors that can function to address the requirement of job burden, fulfil job tasks, alleviate depressed feelings [12
], increase sense of accomplishment and improve individuals’ ability. Examples are high personal job skills, job autonomy, fair treatment, future development, work stability, work identity, sense of respect, income and social support. Enough capital is an important guarantee of occupational groups fulfilling occupational tasks; capital is directly related to their well-being [23
In addition, employees’ depression and well-being might also be regulated by differences in individual personality [24
], especially by the trait of inability to withdraw from obligations at work [25
]. For example, people who are too concerned about work might be more sensitive to the reaction of depression than others. Job burden and capital should be matched in professional life to ensure the staff’s completion of assignments and their well-being and satisfaction.
The present study explores a more comprehensive and systematic association between occupational stress and depression or well-being by proposing the innovative model of job burden-capital. Three hypotheses are to be confirmed: (1) Job burden and capital directly relate to employees’ depression and well-being; (2) Personality can mediate the relationship between job burden-capital and related health outcomes; (3) For occupational groups, the theoretical model has general applicability among populations with different characteristics, and this buffers effects on the model’s association of variables.
Generally speaking, the job burden-capital model is the reform of mainstream models. It avoids some of limitations of the JDC model or the ERI model. The JDC or the ERI model focuses on limited aspects of work-related stressors, and this might initially lead to ignorance of the impact on the occupational population’s health by other working conditions [20
]. However, the burden-capital model, in terms of job burden, integrates occupational psychological demands and workload, making the assessment of extrinsic risking conditions more comprehensive than the “job demands” of the JDC model. That is, the working condition of job burden can be reflected more comprehensively in terms of stressors during work, thus expanding the scope of application to the occupational population. Similarly, in respect to the extrinsic stress protective factor—job capital, sense of control at work (e.g., job skills, autonomy), social support and social exchange (e.g., respect, fairness, identity, income) are included. In turn, this reflects, under a particular job burden level, the impact on occupational stress and even health damage’s occurrence or development by job capital. Notably also, compared with the job demand-resource model, the job burden-capital model has identified that the occupational population’s individual personalities are also an important intrinsic factor in occupational stress’s occurrence or development. The role of personality in the relationships of psychological working conditions and health outcomes (depression or well-being) has been simultaneously verified.
By reviewing theoretical models of occupational stress (e.g., job demand-control-social support model, effort-reward imbalance model), job burden-capital-personality model of occupational stress summarizes specific working conditions as follows: the dimension of job burden that increases risk of depression and reduces well-being, and the dimension of capital that reduces risk of depression and improves well-being. Individual characteristics play an intermediary role in the relationship between working conditions and health outcomes. The latent variable of job burden is mainly measured based on the following:
Workload and psychological demands, such as over tasking, time pressure and complex operations, which might directly or indirectly increase risk of occupational stress’ occurrence and development;
Capital, which mainly includes job autonomy, skills, social support, feedback, job stability and job prospects, such as personal job skills, job autonomy, fair treatment, future development, work stability, sense of identity, respect sense, income and social support;
Dimension of personality that mainly involves the three typical characteristics of overwhelmed, laid-back, and postponing.
Analysis of sub-items’ internal consistency reliability show that selected variables or dimensions have good internal consistency. Hypothesis 1 proposed that job burden and capital can be directly associated with depression and well-being. Correlation and SEM analyses show that job burden positively correlates to depression, in other words, a higher burden is directly associated with greater depression and lower well-being. Similarly, increased capital significantly relates to risk of depression and increased well-being, which has negatively correlates with job burden [31
]. Moreover, job burden and capital could also indirectly affect depression and well-being through personality. Indirect effects alter in different variables, of which job burden has stronger indirect effects than job capital. In other words, job burden influences personal characteristics more to affect occupational outcomes indirectly.
Hypothesis 2 proposed that the individual personality might mediate the relationship between job burden-capital and depression-well-being. TaruFeldt’s work indicates that participants with low over-commitment as a certain personal characteristic with a set of attitudes reflecting excessive striving combined with a strong desire for approval [38
] tend to score higher in well-being [39
]. Individual personality, such as exaggerating their efforts beyond levels or exposing high demands at work too often, might reduce potential to recover from job demands and increase susceptibility to frustration [40
]. In addition to direct influences on occupational outcomes, results show that individual personality could also mediate effects between job burden-capital and outcome of working status.
Analysis of multi-group SEM shows that the model has good applicability to different genders, ages, education levels, marital statuses and positions. According to good applicability, we can detect these variables differentiated effects. Results show that gender, marriage and education load significantly different coefficients of the path from job burden to depression, indicating that such variables act as adjusting roles for the association between these two aspects. In other words, single male employees with a low educational level might weaken health effects of depression caused by a job burden. Similarly, we found that the male gender is also a risk factor for depression by personality, and a single employee shows fewer preventive effects with decreasing burden.
The next deduction might be obtained through comparison of job burden and capital’s direct effect on outcome. That is, capital has a more obvious effect on depression and well-being; this result is similar to some existing research. In both the JDC model and the demand-resource model, job demands’ impacts on job strain could be buffered by job control/resources [12
]. Additionally, the JDC neglected control’s role in affecting occupational outcomes until Bakker indicated that job resources are not only essential for dealing with job demands, but they have influencing effects in their own right as well [12
]. In other words, job capitals either play an intrinsic motivational role because they promote employees’ growth, learning and development or play an extrinsic motivational role because they are helpful in achieving work goals [12
]. This indicates that employees with adequate capitals for work tasks will probably be obtained and completed [43
], consistent with either previous stress theory or our model. That is to say, job burden, a major source of tension, might play a role in depression and well-being, while capital is necessary to adjust health outcomes, work efficiency or motivation. Furthermore, the correlation coefficient indicates interactive effects between them in development of occupational outcomes [43
In the job burden-capital model, psychological working conditions in different dimensions are now comparable; that is, workload versus psychological demand, effort versus control or social support can be compared and explained within a unified index under a common framework. Results of the measurement model by structural equation analysis have also tested this conclusion: the loading of each measurement dimension in the job burden-capital model is greater than 0.50, i.e., the contribution of corresponding stress factors to psychological working conditions is quite even, and thus comparable. This provides a reliable research platform for further exploring psychological working conditions’ impact on health. Based on this platform, this article has measured the extrinsic stress factor—job burden—and the extrinsic protection factor—job capital. Thus, it clarified the relationship between burden/capital and depression/health. That is, an increase in either psychological needs or working task requirements of job burden might directly damage health, while increase in capital might have protective effects on health. From another point of view, the result reflects the model’s flexibility in use. More specifically in the present study, different dimensions of stress have different roles in depression and health status, helping healthcare workers or enterprise managers identify populations at high risk of depression; for example, single male employees with low educational levels might weaken the health effects of depression caused by job burden. The application of the JBC model in stress study might deepen our understanding of depression’s health damage and help distinguish different stress characteristics among different occupational populations.
In the future, this model can be used to investigate occupational stress and its health impacts on a broader occupational scope and to explore its reliability and validity in different occupational groups. At the same time, it will be meaningful to improve the model’s measurement indicator system continuously and to ameliorate the theoretical framework for comprehensive reflection of work-related stress among occupational populations. Moreover, the model is helpful in detecting modifiable conditions such as skill, social support or even personality related to work, which employers could promote through professional training and culture construction. Thus, practical evidence for health intervention under the job burden–capital model must be illustrated in future studies, and the model’s reliability and validity remain to be further investigated before application in other language contexts.