A critical analysis of the intent-to-treat principle in prevention research

Nonadherence to experimental protocols in randomized clinical trials (RCT) is a ubiquitous problem that can lead to erroneous estimations of treatment effects. The most widely advocated strategy for addressing the problem of nonadherence is based on the principle of intent-to-treat (ITT) in which all participants are analyzed according to their randomized condition regardless of actual adherence to the assigned protocol. However, there are numerous problems with using the ITT principle, all of which can be magnified in prevention RCTs. We describe the rationale underlying the use of the ITT principle and the potential problems it can create when interpreting results from prevention RCTs. Four alternative solutions for analyzing nonadherence to experimental protocols that would advance the science and practice of prevention are described. Editors' Strategic Implications: This paper details a strategy that shows promise. This paper speaks to all research methods when treatment and comparisons are involved. The authors' recommendations for analyzing nonadherence to protocols - in both experimental and control conditions - are sound; if followed, they would improve research practice and push the knowledge base forward about how to ensure translation from research to practice. The authors' lessons may be just as relevant to researchers in applied settings as they are to those conducting clinical trials.