Assessing Core Beliefs in Adolescence: Psychometric Validation of the Negative Core Beliefs Inventory (NCBI)

<b>Background:</b> Core beliefs, per Beck's cognitive theory, are fundamental views of self and others that shape emotion. Although the Negative Core Beliefs Inventory (NCBI) is validated in adults, evidence in adolescents-a key period for belief formation-remains limited. <b>Objective:</b> Validate the NCBI for adolescents by testing factorial structure, reliability, and validity. <b>Methods:</b> 146 students (12-17) in Salvador, Brazil, completed the NCBI plus anxiety, depression, and life satisfaction measures. Analyses included expert content review, EFA/CFA, graded response and generalized partial credit IRT models, and EBICglasso network modeling. <b>Results:</b> CFA supported the two-factor solution with acceptable fit (CFI = .89; RMSEA = .056). Internal consistency was good (most ω > .70); nCB-O ω = .87 and overall nCB-S ω = .93, but helplessness/vulnerability was lower (ω = .64). IRT indicated adequate discrimination for most items and greater information at higher trait levels; nCB-S9 performed poorly. Networks showed expected associations with anxiety, depression, and life satisfaction, supporting concurrent validity. <b>Conclusions:</b> The NCBI appears suitable for assessing negative core beliefs in adolescents and may aid early identification and intervention. Targeted refinement-particularly of nCB-S9 and the helplessness/vulnerability subscale-could strengthen psychometrics for this population. Broader samples and longitudinal designs are warranted to confirm stability and predictive validity.