The self-employed are a relatively small, but important group of workers. They contribute to society and its economy through growth, innovation, and job-creation. Self-employed work is characterised by working for oneself; it is associated with high levels of autonomy, but also uncertainty about income, high demands, and sometimes lack of social context at work. This may lead to strenuous work situations and thus impaired health, which over time can affect work negatively, in a reciprocal relationship where health and work affect each other. Despite the importance of self-employed workers, health and the unique circumstances of self-employed work are still understudied. Further, while they are a diverse group, this heterogeneity has seldom been considered in earlier research. 

This thesis investigates health in terms of wellbeing, illbeing, and self-rated health in relationship to work and demographic characteristics, entrance into, and exit out of self-employment, thereby taking the heterogeneity of self-employed workers into account. The thesis comprises three studies based on survey data to: compare mental illbeing in self-employed workers, organisationally-employed workers, and those combining the two types of work (Study I); study the health of workers engaging in self-employment over time (Study II); and compare wellbeing and its relationship to experiences of work in self-employed and organisationally-employed workers (Study III). In all studies, advanced statistical methods using the Bayesian approach were applied to accurately model the complexity of the longitudinal or multilevel data.

In Study I, we found that illbeing in self-employed, organisationally-employed workers and combinators does not substantially differ. In Study II we demonstrate that workers engaging in self-employment belong to four distinct health profiles, which they also mostly maintain over time. Furthermore, entrance into and exit out of self-employed work, and work characteristics, but not demographic characteristics, are related to these health profiles of the self-employed. Lastly, in Study III, we found that experience of self-determination and meaning during the performance of work tasks have stronger associations with wellbeing than employment type (self-employed or organisationally employed).

In summary, this thesis shows that there are few substantial differences in illbeing between organisationally-employed workers, self-employed workers, and combinators. Further, and perhaps explaining some of these results, there is variation in the health of self-employed workers, both between different individuals, and over time, indicating that heterogeneity among self-employed workers is substantial. Lastly, also further explaining why health differences between workers of different employment forms are small, differences in wellbeing between self-employed and employed workers can be explained by the tasks that these workers perform during the day, beyond that of their employment form.

This thesis shows the importance of taking aspects of health, time, heterogeneity of workers, and assessment of these into account to gain more in-depth understanding of the interrelations between health and self-employed work.