Abstract
BACKGROUND: Obsessive-compulsive personality disorder is a chronic condition characterized by a maladaptive pattern of excessive perfectionism, preoccupation with rules and details, and the urge to control the environment, which results in significant distress or impairment, especially in interpersonal functioning. Individuals diagnosed with the mentioned disorder are often seen as rigid, inflexible, and highly controlling. Therefore, the present study aims to investigate the effectiveness of unified transdiagnostic interventions based on common mechanisms of obsessive personality patterns. MATERIALS AND METHOD: This quantitative research is a semi-experimental single-case and multiple-base design with asynchronous participants. Five participants were selected using purposive sampling through semi-structured interviews based on DSM-5 among patients who visited the clinics during 2022-2023. The research included the Millon Clinical Multiaxial Inventory. Moreover, the treatment intervention was administered individually throughout 12 sessions with one session a week. Data analysis involved visual inspection or graphical representation of each case's improvement percentage and change index. RESULT: The results from visual representation indicated that the transdiagnostic intervention based on common mechanisms significantly influenced the obsessive personality patterns at baseline, during treatment, and at follow-up. There was a significant change in the reliable change index compared to the baseline for all five participants. During the treatment phase, participants showed a mean score of 30.28 for the obsessive personality pattern, indicating a significant level of effectiveness. However, the mean score increased to 57.50 at the follow-up stage. CONCLUSION: According to Blanchard and Schwartz's classification, the unified transdiagnostic interventions based on common mechanisms and their effectiveness on obsessive personality patterns fell into the improvement category during treatment and into the success category at the follow-up stage of the study. Overall, the findings suggest a bright future for the treatment of individuals with obsessive personality patterns, as unified diagnostic interventions show great potential for significant impact.