I came across this idea that I've never heard of in the study of Li et al. (2023), just a brief context, it's a review on the relationship between epistemic trust and developmental psychopathology.
In their section of "Epistemic Trust and Mental Health". Their first few lines prompted my question of using a proxy measure, specifically they examined multiple studies which used a trust subscale as a proxy measure for epistemic trust. Therefore, I'm just wondering how would that work? It sounds like to me there's alot more disadvantages than advantages since you're using a slightly different variable, but of course, I might be very wrong on this so I welcome any new insights.
Ref: Li, E., Campbell, C., Midgley, N., & Luyten, P. (2023). Epistemic trust: a comprehensive review of empirical insights and implications for developmental psychopathology. Research in Psychotherapy, 26(3). https://doi.org/10.4081/ripppo.2023.704
Using a proxy measure means using a related variable to indirectly measure the one you're interested in. This is often done when direct measurement is difficult.
For example, using the number of steps taken per day as a proxy for physical activity levels.