Cognitive bias modification Utilised to Rectify Errors for Depression (CURED): a double-blind, parallel-group feasibility randomised controlled trial in adults with depression

Background: Depression is a leading cause of global disability, yet access to evidence-based treatments such as CBT remains limited due to shortages of trained clinicians. Scalable, low-cost interventions offer a potential solution. Cognitive Bias Modification for Interpretation (CBM-I) is a promising candidate that is grounded in cognitive theory and backed by evidence. However, effects in depression have been weaker. To address previous limitations, we recently developed CURED (Cognitive bias modification Utilised to Rectify Errors for Depression), a six-session intervention co-developed with individuals with lived experience of depression and refined with clinician input. This study aims to evaluate the feasibility, acceptability and safety of CURED.

Methods: This study is a double-blind, parallel-group feasibility randomised controlled trial recruiting 60 adults meeting inclusion criteria for clinical depression. Participants are allocated 1:1 either to the CURED intervention or a neutral CBM-I control matched for format, length, and delivery, though differing in content. Both arms involve six weekly sessions delivered via mailed pen-and-paper booklets, with remote researcher support to ensure fidelity, and assessment at baseline, post-treatment (6 weeks) and 12-week follow-up. Primary outcomes are feasibility (response, recruitment, eligibility, randomisation, retention, weekly assessment completion, adherence, and randomisation rates); acceptability (Credibility and Expectancy Questionnaire, Exit Questionnaire, and qualitative interviews); integrity of blinding; and safety (adverse and serious adverse events). Secondary outcomes include interpretation bias, depressive and anxiety symptoms, cognitive content and processes, and psychosocial functioning. Analyses will summarise feasibility metrics descriptively and provide variance estimates to inform sample size calculations and primary outcome selection for a future definitive trial.

Discussion: CURED has the potential to address the pressing need for accessible, evidence-based interventions for depression. This feasibility trial will establish whether CURED is feasible, acceptable, and safe. If successful, a fully powered, definitive efficacy randomised controlled trial will be warranted.

Trial registration: ISRCTN51689816, https://www.isrctn.com/ISRCTN51689816. Prospectively registered on 16 June 2025. Recruitment started on 16 July 2025 and is anticipated to be completed by 1 July 2026.