What qualitative research can contribute to a randomized controlled trial of a complex community intervention

Using the case of a large-scale, multi-site Canadian Housing First research demonstration project for homeless people with mental illness, At Home/Chez Soi, we illustrate the value of qualitative methods in a randomized controlled trial (RCT) of a complex community intervention. We argue that quantitative RCT research can neither capture the complexity nor tell the full story of a complex community intervention. We conceptualize complex community interventions as having multiple phases and dimensions that require both RCT and qualitative research components. Rather than assume that qualitative research and RCTs are incommensurate, a more pragmatic mixed methods approach was used, which included using both qualitative and quantitative methods to understand program implementation and outcomes. At the same time, qualitative research was used to examine aspects of the intervention that could not be understood through the RCT, such as its conception, planning, sustainability, and policy impacts. Through this example, we show how qualitative research can tell a more complete story about complex community interventions.