Contagious Interactions : Essays on social and epidemiological networks

Abstract: This dissertation has two overall aims; to explore and develop the use of SNA in sociology, and to demonstrate that sociology has much to give to other sciences. Interdisciplinary collaboration is necessary because we do not live in a world in which subject areas are strictly isolated. Human beings are social animals, and a sociological understanding is crucial in all human-related science. The examination in this thesis of different kinds of social networks and how they affect the lives of individuals (and vice versa) will provide knowledge both in the development of methods for analyzing social networks, and in their areas specific scientific areas.Paper I-III investigates sexual networks and how the number of sexual encounters involving intercourse in combination with the number of sexual partners affects the dynamics of sexually transmitted infections (STIs). The results show that this relationship is non-linear, indicating that it may not be the individuals with the largest number of partners who have the most impact on the spread of STIs. One might also have to focus interventions on individuals who have a large number of sexual encounters involving intercourse per partner, and who have several (but not necessarily a very large number of) partners.In the fourth paper, we apply the theoretical concept of so-called small worlds to a sexual network. The spread of epidemics can be difficult to stop in such networks, and we show that the sexual network of individuals infected with chlamydia can be characterized as such.The fifth and last paper differs from the four first. In this paper, we focus on how individuals who committed suicide in Stockholm during the 1990s where connected to each other. The social-interaction exposure effect is larger for the individual within the family than at the workplace; yet work-domain exposure is more important for the overall suicide rate because individuals are more often exposed to suicides of co-workers than family members.