Treatment-as-usual in effectiveness studies: What is it and does it matter?

A hallmark of an evidence-based practice (EBP) is the systematic appraisal of research related to the effectiveness of interventions. This study addressed the issue of interpreting results from effectiveness studies that use treatment-as-usual (TAU) as a comparator. Using randomised controlled studies that evaluate the effectiveness of multisystemic therapy as an illustrative example, we show that TAU includes a wide variety of treatment alternatives. Estimated treatment effects on recidivism suggest that TAU seems to contain a greater variation in underlying risk than experimental conditions, supporting the hypothesis that the content of TAU could affect outcomes. Implications for the realisation of an EBP are discussed.