As young people transition to adulthood, their constellation of social ties evolves. Although some studies on health behavior consider overall levels of social connection in adulthood, most focus on specific social ties, especially the marital relationship. Lower mortality rates among the married are often attributed, in part, to better health habits (Rogers 1995, Waite & Gallagher 2000). Indeed, the transition into marriage is associated with a reduction in risky health behaviors, including problem drinking, drug use, and smoking (Bachman et al. 2002, Chilcoat & Breslau 1996), and studies show that the married engage in less risky health behavior generally, compared with the unmarried. At the same time, however, the married weigh more and exercise less than the unmarried (Grzywacz & Marks 1999, Jeffery & Rick 2002, Umberson 1992). In fact, Smith & Christakis (2008) find that having an obese spouse increases one’s own obesity risk by 37%. Some studies suggest that the benefits of cohabitation for health habits are similar to those of marital ties (Wu et al. 2003). Duncan and colleagues (2006) find that, among young adults, the transition
