Multidimensional transdiagnostic inventory of psychopathology: development and initial validation

Traditional diagnostic systems, such as the DSM-5 and ICD-11, suffer from well-documented limitations, including high comorbidity rates, arbitrary diagnostic thresholds, and within-disorder heterogeneity. Consequently, the field is evolving towards hierarchical, transdiagnostic, dimensional models of psychopathology. This study reports on the development and initial validation of the Multidimensional Transdiagnostic Inventory of Psychopathology (MTIP). This new broadband inventory aligns traditional DSM disorders with contemporary dimensional models of psychopathology. We conducted initial development and basic psychometric analyses in a mixed sample of 301 adults. We then validated the MTIP in a second independent sample (N = 826), of which 640 who self-reported no history of past mental health treatment were used as our normative/reference sample. The final MTIP contained 13 clinical scales and seven supplemental scales. All the MTIP scales met core psychometric assumptions at the item, scale, and transdiagnostic levels. A series of exploratory and second-order factor analyses supported the MTIP hierarchical dimensional structure. Concurrent validity correlations with the DSM-5 level 1 cross-cutting symptom measure were strong, ranging from 0.89 (depression) to 0.51 (drug misuse). Regression analyses supported the construct validity of the higher-order transdiagnostic scales. Twelve of the 13 clinical scales differentiated individuals with a history of mental health care from those without past care, with effect sizes ranging from 0.20 (Alcohol Misuse) to 1.06 (Anxiety). Effect sizes for the transdiagnostic scales ranged from 0.33 (Thought Dysregulation) to 1.07 (Emotion Dysregulation). The clinical implications and potential applications of the MTIP are discussed.