Adaptation of the “Osnabrück Scale for Therapy Adjustment and Identification of Psychological Complaints in Schizophrenia-OSSTI-TR” into Turkish culture and investigation of its psychometric characteristics

Aim: This study aims to adapt the "Osnabrück Scale for Therapy Adjustment and Identification of Psychological Complaints in Schizophrenia" (OSSTI) into Turkish and evaluate its psychometric properties. The study addresses the need for a practical self-report tool to simultaneously assess metacognitive awareness and treatment adherence in Turkish patients with schizophrenia. Methods: Data were collected from 335 patients diagnosed with schizophrenia. Following translation and back-translation, content validity was confirmed via expert panel. Construct validity was tested using Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA). Reliability was assessed through Cronbach's alpha and split-half coefficients. Results: EFA identified a three-factor structure-Awareness, Denial, and Adjustment-explaining 58.03% of the total variance. While initial single-factor CFA was rejected, the final model demonstrated acceptable alignment with the theoretical framework. The scale's overall internal consistency was Cronbach's α = .73, with subscale coefficients ranging from .70 to .78. Convergent validity was supported by a significant moderate correlation with the Morisky Medication Adherence Scale (r = -.418, p