RT Journal Article T1 Developing an accurate and efficient tool for the internalizing spectrum: A simulation study of the adaptive algorithm to the Inventory of Depression and Anxiety Symptoms II (IDAS‐II) A1 Rosa Cáceres, Ana María A1 Rossi, Gina A1 Díaz Batanero, María Carmen A1 Sánchez García, Manuel AB Objectives: This research simulates an adaptive version of the IDAS‐II (IDAS‐CAT).Methods: 2021 participants from both community (n = 1692) and patients (n = 329)samples completed the IDAS‐II. Item response theory metric properties of theIDAS‐II full test and the 20‐items of the general depression (GD) scale were obtained.The efficiency and accuracy of different computerized adaptive algorithmswere simulated. Different subsamples completed additional external measures inorder to gather evidence of validity of the scores estimated with the simulatedadaptive algorithms selected.Results: Both unidimensional computerized adaptive testing algorithm selected fortheGDscale and the bifactor model chosen for the full test, allow70%reduction in thelength of administration, maintaining a measurement error below 0.30 on the generaland 0.50 on the specific factors. Results show high correlations of the scores estimatedwith the adaptive algorithms and the estimates based on the full test, as well as correlationswith external criteria almost equal to those generated with the full test.Conclusions: IDAS‐CAT could be a reliable and fast tool for measuring internalizingspectrum. PB Wiley YR 2024 FD 2024 LK https://hdl.handle.net/10272/24262 UL https://hdl.handle.net/10272/24262 LA eng NO Sanchez‐Garcia, M., Rosa‐Cáceres, A.M., Rossi, G., & Diaz‐Batanero, C. (2024). Developing an accurate and efficient tool for the internalizing spectrum: A simulation study of the adaptive algorithm to the Inventory of Depression and Anxiety Symptoms II (IDAS‐II). International Journal of Methods in Psychiatric Research, e2032. https://doi. org/10.1002/mpr.2032 NO Ministerio de Ciencia e Innovación (MICIU/AEI/10.13039/501100011033), Grant/AwardNumber: PID2020‐116187RB‐I00; Ministeriode Universidades, Grant/Award Number:FPU19/00144 DS Repositorio Institucional de la Universidad de Huelva RD 30 may 2026