Todays workers are living in a rapidly changing environment and adaptability has become one of the most valued competences. Because of economical competition, demands imposed on workers are getting more and more elevated. The opposition between constraints of efficiency, search for performance, workload and private life, combined with a loss in work meaning and in social support, contribute to expose workers to job stress and burnout. Besides dealing with high workload and exigencies of adaptability, workers are expected to create their own career opportunities and development. More specifically, in order to stay competitive, organizations need workers that are active and creative at work, workers that are ready to invest not only their time, but also their mind into their work. In other words, they need workers to be engaged in their work. Given this apparent opposition between increased risk for job stress and burnout on the one hand, and increased need of engaged workers on the other, it is necessary to investigate which conditions are prevalent in the development of those phenomena. In this thesis, we present a theoretical overview of burnout and engagement concepts (chapter1 and chapter2, respectively). We then expose how they are integrated into the theoretical framework of the Job Demands-Resources (JDR) model, and what criticism it can be addressed (chapter3). Chapter4 is dedicated to our research objectives, which are declined in five empirical studies. In study1(chapter5) and study2 (chapter6), we aim at validating the Positive and Negative Occupational States Inventory (PNOSI), a tool that was designed to measure positive and negative workers reactions to their working environment. Results indicate that the tool is composed of two factors, one measuring negative occupational state and the other measuring positive occupational state. This structure was replicated on a variety of samples. Negative occupational state can be conceived as an intermediate state occurring before burnout, while positive occupational state seems to be similar to work engagement. Both are different from commitment and workaholism. The impact of item wording, and interactions between items on the one hand and gender and age on the other were also investigated. In study3 (chapter7), we aim at validating the JDR model on three-wave longitudinal data that we collected among workers of a Belgian public administration. In addition, this study aims at validating the JDR model using predictors derived from stigma and social identity literature. Results indicate that perceived prejudice predicts higher burnout, whereas group identification predicts higher engagement. This was found above the effects of job demands and job resources, respectively. An interaction effect was also observed: among those who identify strongly to their occupational group, engagement was lower when workers also perceived high prejudice towards this group. Study4 and study5 also aim at validating the model using new types of predictors. Study4 (chapter8) more specifically focuses on the health-impairment process of the JDR model. It investigates whether person-related factors (namely workaholism) predict burnout in addition to job demands. Study4 also longitudinally testes whether job strain can indeed be considered as an intermediate state occurring in response to high job demands before burnout develops. We found that job strain acts as an intermediate, shorter term reaction to high job demands, before the occurrence of burnout. Results were mitigated as to the role of workaholism. It was hypothesized that this variable would initiate another kind of process, dealing with person-related issues. In study5 (chapter9), we focus more specifically on the energetic process, and investigate whether workers work-related personal demands (namely, the expectations they develop with regards to their own performance) predict engagement above the effects of job and personal resources. Results indicate that work-related personal demands predict high future engagement, above the impact of job and personal resources. However, no reciprocal impact of engagement was observed. We end this thesis with a discussion of our results and a general conclusion.

De nombreuses organisations contemporaines cherchent à développer l’engagement dans letravail de leurs employés en tant que moyen de générer un niveau élevé de performance. Surla base des recherches antérieures sur l’engagement au travail, la présente étude examine larelation entre l’engagement dans le travail d’un échantillon de salariés et ses antécédents etconséquences.Engager les employés peut permettre d’aboutir à la création d’un état d’esprit volontaristechez les employés, susceptible de développer leur motivation. Pour créer un tel état d’esprit,différents modèles sont présentés dans la thèse. Le modèle des demandes et ressources estensuite privilégié. Sur la base de ce modèle, il apparaît que les organisations peuvent agir surl’engagement dans le travail en diminuant les exigences du travail (par exemple, la surchargede travail, l’insécurité de l’emploi, etc.) et en augmentant les ressources d’emploi (parexemple, l’autonomie, le perfectionnement professionnel, etc.). Dans cette recherche, nousavons cherché à vérifier notre hypothèse d’une relation entre l’engagement dans le travail etcertains antécédents et conséquences. Nous concluons que, parmi les antécédents étudiés, lacroissance des ressources personnelles est la plus efficace au niveau de ses conséquences surl’engagement dans le travail et la qualité de vie au travail. / Many contemporary organizations are placing a greater emphasis on their employees’engagement at work as a means of generating higher levels of organization performance.Drawing on previous research on work engagement, the present study investigates therelationship between work engagement and its antecedents and consequences. Engaging theemployees will result in creating a willingness feeling in employees, leading to performing alltheir time and energy on their duties in such a way that they don’t realize the passing of time.To create such feelings within employees, different theories have been presented, amongwhich the job demand-resource is a major instance. Based on this model, organizations makework engagement through decreasing job demands (e.g. work overload, job insecurity, etc.)and increasing job resources (e.g. autonomy, professional development, etc.). In this research,we analyze our hypotheses that work engagement has specific antecedents and consequences.We conclude that, out of its antecedents, growth of personal resource has the most effect onwork engagement, as well as on the quality of work life.