A tablet-based attentional cognitive bias modification intervention for positive emotion processing in major depressive disorder: a single-blind randomised controlled two-centre trial.

BACKGROUND: Patients with Major Depressive Disorder (MDD) exhibit biased information processing. This study investigates the clinical and neural efficacy of a cognitive bias modification (CBM) training in patients and healthy control (HCS), fostering processing of positive emotion stimuli. METHODS: In a single-blind randomised controlled trial (DRKS00029756), MDD outpatients and HCS, aged 18-60 years, were randomised to positivity training (PT) or control training (CT). Randomisation was carried out by study assistants, blinding researchers. Participants underwent 10 tablet-based dot-probe sessions over 14 days. PT implicitly redirected attention toward positive stimuli to improve depressive symptoms. Primary outcome was pre and post-training EEG-derived Early Posterior Negativity (EPN), investigating neural sensitivity towards positive stimuli. Secondary clinical outcomes included changes in depression symptoms. FINDINGS: From February 2023 to October 2024, 240 participants were included (119 MDD; 121 HCS). 62 MDD and 61 HCS underwent PT; 57 MDD and 60 HCS received CT. In MDD, EPN to positive high arousal stimuli revealed an interaction between time (pre/post) and training (PT/CT), F(1,97) = 5.017, p < 0.028, η2 = 0.049. The between-treatment difference was 1.65 μV, 95% CI [0.19, 3.11]. EPN amplitudes shifted towards negativity in PT and positivity in CT. Depression symptom decreased from pre to post and from pre to follow-up. With respect to adverse events, one patient in the control training was regularly admitted to hospital. INTERPRETATION: CBM positivity training was associated with neural changes in MDD, supporting its potential to target pre-attentive positive emotion processing. Further EEG follow-up and higher stimulus contrasts in the training conditions may clarify clinical relevance. FUNDING: Funded by DFG (ID: 507720021).