“…While various brainPAD studies have externally validated their models (Beheshti et al, 2018;Cole et al, 2015;Cole, Ritchie, et al, 2018;Cole, Underwood, et al, 2017;Franke et al, 2010;Gutierrez Becker et al, 2018;Lancaster, Lorenz, Leech, & Cole, 2018;Liem et al, 2017;Madan & Kensinger, 2018;Varikuti et al, 2018), only a few studies have reported model performance in terms of accuracy (i.e., correlation or mean absolute error between brainpredicted age and chronological age) on the external validation dataset (Cole et al, 2015;Lancaster et al, 2018;Liem et al, 2017;Madan & Kensinger, 2018). This does not necessarily cast doubt on the validity of the models whose accuracy is reported in terms of internal crossvalidation performance.…”