Social epidemiology for the 21st century.

Social epidemiology, as defined by the textbook of the same name (Berkman et al., 2014) is "that branch of epidemiology concerned with the way that social structures, institutions, and relationships influence health" (p. 2). As our Special Issue commemorates the 50th anniversary of Social Science & Medicine, it is worth noting that the Social Epidemiology office within the journal has existed only for a fraction of that time (fifteen years). So what has been learned in the fifteen years since the establishment of the new office? In this commentary, we spotlight some of the achievements, substantive topics, and future trends in the research papers that we have featured in our Section of the journal.