The dark side of social capital: A systematic review of the negative health effects of social capital.

There is a growing literature demonstrating the health benefits of social capital (defined as the resources accessed through social connections). However, social capital is also acknowledged to be a "double-edged" phenomenon, whose effects on health are not always positive. We sought to systematically review studies that have found a negative (i.e. harmful) association between social capital and health outcomes. Our objective was to classify the different types of negative effects, following a framework originally proposed by Portes (1998). We conducted a literature search in Pubmed, Embase and PsychInfo. We identified 3530 manuscripts. After detailed review, we included 44 articles in our systematic review. There are at least two negative consequences of social capital besides the classification proposed by Portes: behavioral contagion and cross-level interactions between social cohesion and individual characteristics. When leveraging the concept of social capital for health promotion interventions, researchers need to take account of these potential "downsides" for health outcomes.