Key words
cancer, anhedonia
CANCER
Given the scale of the global mental health burden, we need time- and resource-efficient methods for the development, testing, and optimization of psychological interventions. However, this need stands in contrast to the present reality: The standard route for treatment development is slow and inefficient; typically proceeding via initial single case or cohort designs followed by a series of 2- or 3-arm randomized controlled trials (RCTs), this process is essentially the same as it was a few decades ago and is unable to keep pace with the demand for improved outcomes in mental health. In other areas of health, such as cancer, recognition of the need for more rapid treatment development has led to the creation of a new generation of alternative research designs (e.g. Hobbs, Chen, and Lee, The leapfrog design can be considered a simple form of an ‘adaptive platform trial’ (Angus et al., How does a leapfrog trial work? In such a trial, multiple treatment arms can be tested simultaneously, with one designated as the comparison arm or control. As the trial proceeds and data accumulates, sequential Bayes Factors (BFs; e.g. Schönbrodt, Wagenmakers, Zehetleitner, and Perugini, We therefore aimed to conduct a leapfrog trial to provide a concrete demonstration from pre-registration to final reporting, as well as to ascertain the design's feasibility and identify any potential problems or adjustments needed. We applied the design to an internet-delivered cognitive training intervention, imagery cognitive bias modification (imagery CBM; Blackwell et al., In applying the leapfrog design to imagery CBM as a low-intensity intervention to reduce anhedonia, our primary aim in this study was to implement and thus demonstrate the core features of a leapfrog trial: Sequential Bayesian analyses based on Bayes Factors (BF), updated continuously with each new participant completing the trial; removal of a trial arm when it hit a prespecified threshold for failure; introduction of new trial arms into an ongoing trial; and replacement of the control arm with a different arm when that intervention arm reached a pre-specified threshold for success.