Fig. 1

Conceptual framework for mental model-based repeated multifaceted (MRM) intervention design. The MRM framework is based on major concerns cited in existing systematic and scoping reviews, trials, and recent empirical studies regarding the approaches, frequency, treatment components, sample balance variables, and time dimensions of treatment interventions, especially WASH-related field experiments (Table 2). It considers mental model mapping to be essential and further includes two core ideas, namely, multifaceted intervention and repeated interventions, to develop this modified intervention design