Invited commentary: social capital, social contexts, and depression.

The literature concerning social capital and health has grown exponentially during the past somewhat more than 10 years. The study by Kouvonen et al. (Am J Epidemiol 2008;167:1143-1151) is a longitudinal multilevel analysis of 33,577 public sector employees in Finland. The study shows a significant association between workplace social capital and depression, which is an interesting finding in a very new field of the study of social capital and health. However, the study also serves as an inspiration for further studies in important research areas. Workplace social capital may be investigated according to both horizontal, that is, social contacts and level of trust in relation to coworkers, and vertical, that is, relation with employer/supervisor across power gradients, dimensions. The fact that workplace social capital may affect social capital outside work and vice versa is also of interest. It is also important to define and identify the social context level in a correct way in multilevel studies. In the study by Kouvonen et al., the social context is not a geographic entity but an entity defined according to place of work, and the definition of such a social context entails several difficulties. This study presents interesting findings and provides a basis for future studies.