Cognitive bias modification for interpretation (CBM-I) for post-traumatic stress disorder: study protocol of an app-based randomised controlled trial

INTRODUCTION: Previous studies indicate that computerised trainings implementing cognitive bias modification (CBM) for interpretation bias might be promising treatments for trauma-related cognitive distortions and symptoms. However, results are mixed, which might be related to the implemented task (sentence completion task), setting, or training duration. Within the present study, we aim to evaluate the efficacy and safety of an app-based intervention for interpretation bias using standardised imagery audio scripts, which is designed as a standalone treatment. METHODS AND ANALYSIS: The study is a randomised controlled trial, implementing two parallel arms. 130 patients diagnosed with post-traumatic stress disorder (PTSD) will be allocated to either the intervention group or the waiting-list control group receiving treatment as usual. The intervention consists of 3 weeks of an app-based CBM training for interpretation bias using mental imagery, with three training sessions (20 min) per week. Two months after the last training session, 1 week of booster CBM treatment will be implemented, consisting of three additional training sessions. Outcome assessments will be conducted pretraining, 1 week post-training, 2 months post-training, as well as 1 week after the booster session (approximately 2.5 months after initial training termination). The primary outcome is interpretation bias. Secondary outcomes include PTSD-related cognitive distortions and symptom severity, as well as negative affectivity. Outcome assessment will be conducted by intention-to-treat analysis, as well as per-protocol analysis using linear mixed models. ETHICS AND DISSEMINATION: The study was approved by the Ethics Committee of the State Chamber of Physicians in Baden-Wuerttemberg, Germany (number of approval: F-2022-080). Scientific findings will be published in peer-reviewed journals informing future clinical studies, which focus on the reduction of PTSD-related symptoms using CBM. TRIAL REGISTRATION NUMBER: German Clinical Trials Register (DRKS00030285; https://drks.de/search/de/trial/DRKS00030285).