Although most Cochrane Reviews cover what would be thought of as medicines or healthcare procedures or practices, some look at much more complex interventions. One such example is a January 2013 review from the Cochrane Public Health Group, described here by one of the authors, Nandita Bhan from the Department of Social & Behavioral Sciences at the Harvard School of Public Health in the USA. The review looks at the evidence on the effects of slum upgrading.