It may seem obvious that strained and conflicted social interactions undermine health, but social ties may have other types of unintended negative effects on health. For example, relationships with risk-taking peers contribute to increased alcohol consumption, and having an obese spouse or friend increases personal obesity risk (Christakis and Fowler 2007; Crosnoe et al. 2004). This “social contagion” of negative health behaviors operates via multiple mechanisms (Smith and Christakis 2008). One key mechanism is social norms. Perceived social norms about drinking behavior influence alcohol consumption among young adults (Thombs, Wolcott, and Farkash 1997), and friendship norms about dieting influence unhealthy weight control (Eisenberg et al. 2005). Unsupportive social ties may also present barriers to improving health behaviors and outcomes. For example, Nagasawa and colleagues (1990) found that negative social environments and their perceived barriers predicted poor compliance to medical regimens among diabetes patients.
