Discussion
anhedonia
DISORDERS
This study provides a successful first demonstration of a ‘leapfrog’ trial applied to the development of a psychological treatment, in this case an internet-delivered cognitive training intervention targeting anhedonia, and illustrates its central design features: sequential Bayesian analyses, dropping or promotion of a trial arm on the basis of these analyses, and introduction of new arms into an ongoing trial. These design features could all be successfully implemented, indicating that at least in the context of simple internet-delivered interventions the leapfrog design is a feasible option for treatment development and optimization.How can we interpret the results of such a trial and what would be the next steps? We started with an automated, unguided web-based self-help intervention that had never previously been tested in this format, and tested four possible versions of how to implement it; we ended with one ‘winning’ version that was found to be better at reducing anhedonia than an initial control condition, and whose effectiveness was not surpassed by any other version tested. One option would then be to take this winning arm further forwards in the research process, for example testing it in a definitive (superiority or non-inferiority) RCT against established similar low-intensity unguided web-based interventions to see how it compared to these in reducing anhedonia; if pre-planned, such as step could in fact be added seamlessly to the end of the initial leapfrog trial (Blackwell et al., Selected leapfrog trial advantageous design features and potential challenges illustrated in the current trial55% power to find See Blackwell et al. (The current trial illustrates some of the advantageous features of the leapfrog design for treatment development, as well as some additional challenges and factors researchers may wish to consider in optimizing its application in their own research, summarized in In the current study we demonstrated one specific application of the leapfrog design: a treatment development process aiming to find an efficacious version of a new intervention via testing several different variants. However, via application of the basic principles as illustrated here the design could be applied in many ways across the translational spectrum, from pre-clinical work (e.g. developing optimal versions of experimental paradigms or measures) to large clinical trials testing treatment selection algorithms; the principles could also be extended to non-inferiority or equivalence testing and more complex treatment outcomes such as rate of change or cost-effectiveness (see Blackwell et al., The leapfrog design was conceived and developed in the context of a changing landscape for psychological treatment development: For many disorders the most crucial questions are no longer about whether we can develop an efficacious psychological intervention at all, but rather how we can address the need to increase efficacy and accessibility still further, for example via improved targeting of refractory symptoms, tailoring of treatments to individuals, reducing relapse, and innovating in our basic conceptions of psychological interventions and methods of treatment delivery (Blackwell & Heidenreich, 