Central to the Job Demand Control model is the interaction amid job demands and job control. This has resulted in the identification of four job types; passive jobs, active jobs, low strain jobs and high strain jobs. The least risk to health is found in active jobs with levels of high demand and high control. In contrast, high strain jobs with high demands and low control are the most risky towards an employee’s health. Those in low strain jobs experience below average levels of job strain due to low demands and high control. Passive jobs are those with low demands placed on the employee whilst also possessing low control. The stress hypothesis declares that high demands shared with low control cause stress, therefore it is not surprising to find psychological and physical strain are mostly related to high strain jobs. Furthermore, Karasek (1979) puts forward a learning hypothesis in which the combination of high demands and high control found in an active job can give employees opportunity for growth and development. Therefore, it is clear from the model that high demands are not always detrimental to an employee but in fact can act as a motivator when combined with high levels of control.
The literature provides substantial evidence for the model however, unequivocal results are also present. The major assumptions of the job demand control model are confirmed within epidemiological studies on cardiovascular disease as an outcome variable. Cardiovascular disease is much more prominent in individuals working in high strain jobs (Schnall et al, 1994). Furthermore, the majority of these studies also conclude that high strain jobs are also linked to factors such as high blood pressure and smoking which can cause cardiovascular disease. However, the findings are less conclusive with regards to other outcome variables such as psychological well-being and mental health. Several reasons exist to attempt to explain these less consistent findings. Most prominent is the methodology used in some research. Many studies compared only high demand/low control subgroups (high strain jobs) with high demand/high control subgroups (active jobs) and in turn did not test the interaction effect between demand and control. Moreover, this comparison resulted in significant differences between high strain and active jobs in relation to employee health and well-being (Erikson & Ursin, 1999). However, when testing the interaction effect the job demand control model was supported less repeatedly with some reporting evidence for the model (Sargent & Terry, 1998) and some not (Schaubroeck & Fink, 1998).
In relation to the above inconsistencies found using the job demand control model, Karasek (1979) argued that in order to support the model a statistically significant interaction between job demands and job control is not essential. Karasek stated that the basic principle of the model continues to be supported if job demands and job control both wield independent main effects. Furthermore, reducing job demands and increasing job control would have the result of reducing strain even without the presence of an interaction. Overall, the main criticisms concerning the model are inconsistency and uncertainty with regard to the functioning of the two key constructs within the model; job demands and job control. Also, the models narrow focus on only two of a vast range of workplace characteristics gives excessive burden to the strain hypothesis and applicability to all health related outcomes.
Although conflicting evidence exists towards the model, its use and practicality have allowed it to become one of the dominant theoretical and empirical approaches for relating work organisations to strain and stress in the workplace. One of the main reasons for the models success rests in that it is scientifically clear and easily comprehended by practitioners. However, the models simplicity may also be it weakness as the complex reality of the workplace is unrealistic as it’s reduced to a handful of variables in the model. Much empirical research shows that high demands alongside low decision authority and little opportunity to learn and develop result in a work environment which is detrimental to health (Van der Doef & Maes, 1999). The models ability to predict such working environments is not only beneficial to the employee but also to the workplace as it allows harmful conditions to be eliminated whilst enhancing positive influences. Furthermore, the model is criticised as it does not take individual characteristics into account which could help determine which characteristics in an individual influence psychological alteration to restraints in the workplace. Nonetheless, the practical and beneficial use of the model cannot be overlooked. It goes beyond the health consequences of work but can also give insight into productivity results through looking at motivation factors present in the work environment.
In conclusion, it is clear the job demand control model is one of high practical use which not only examines the health consequences of a toxic work environment but can also examine motivational factors through its active learning hypothesis. This has resulted in the model withstanding the test of time with much empirical evidence to lend its support in many different work environments. Although the theory is not without its criticisms, the model has the ability to predict harmful working environments whilst also identifying positive working conditions in the workplace.
References
Karasek R.A. (1979). Job demands, Job decision latitude and Mental Strain: Implications for Job Redesign. Administrative Science Quaterly, 24, 285-308.
Sargent, L. D., & Terry, D. J. (1998). The effects of work control and job demands on employee adjustment and work performance. Journal of Occupational and Organizational Psychology, 71, 219-236.
Schaubroeck, J. & Fink, L.S. (1998). Facilitating and inhibiting effects of job control and social support on stress outcomes and role behavior: a contingency model. Journal of Organizational Behavior, 19, 167-195.
Schnall, P.L., Landsbergis, P.A. and Baker, D. (1994). Job strain and cardiovascular disease,
Annual Review of Public Health, 15, 381-411.
Van der Doef, M. & Maes, S. (1999). The Job Demand-Control (-Support) model and psychological well-being: A review of 20 years of empirical research. Work & Stress, 13, 87-114.