Inhibition moderates the effect of attentional bias modification for reducing residual depressive symptoms: A randomized sham-controlled clinical trial.

Objectives: Residual symptoms represent risk factor for relapse. Attention bias modification (ABM) may reduce clinical and sub-clinical depressive symptoms, indicating that is may be of relevance when preventing relapse. Current evidence suggests that executive functions may moderate the outcome of interventions targeting depressive symptoms.
Methods: We assessed inhibition and shifting as indicators of executive functioning by means of the Color-Word Interference Test (i.e., "Stroop task"). These baseline characteristics were investigated as moderator of the effect of ABM on depression symptoms in a double-blinded randomized sham-controlled trial of ABM including patients with a history of recurrent depression (N = 301). Inclusion and follow-ups took place from January 2015 to October 2016. The trial was retrospectively registered #NCT02658682 January 2016.
Results: The moderation analysis was based on the interaction term ABM x Stroop. Scaled inhibition scores ≤10.8, but not shifting ability, moderated the effect of ABM compared to sham on clinician-rated depression (HDRS). The difference from the 15th to the 85th percentile of the inhibition score was about 1 HDRS-point, indicating a small effect size. No moderation was found when self-reported depression and AB were the outcome. Post-hoc power calculation indicates risk of Type-II error.
Conclusion: When targeting depressive symptoms, ABM seems to be somewhat more effective in patients with weak inhibitory control. This suggests that evaluating the level of inhibition in individual patients could provide some information when making decisions about prescribing ABM to reduce residual symptoms, but the clinical implications of this is uncertain due to an overall small effect size attributable to ABM. Future studies should examine whether inhibitory control still is a relevant moderator when comparing ABM to treatment options other than the sham control condition.
Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Nils Inge Landro reports financial support was provided by Research Council of Norway. Nils Inge Landro reports financial support was provided by South-Eastern Norway Regional Health Authority. Ragnhild Boe reports financial support was provided by Foundation Dam. Catherine J. Harmer reports a relationship with P1 Vital that includes: consulting or advisory. Catherine J. Harmer reports a relationship with Lundbeck that includes: consulting or advisory. Catherine J. Harmer reports a relationship with SAGE Therapeutics Inc that includes: consulting or advisory. Catherine J. Harmer reports a relationship with Compass Pathways Plc that includes: consulting or advisory. Catherine J. Harmer reports a relationship with Zogenix Inc that includes: consulting or advisory. Nils Inge Landro reports a relationship with Lundbeck that includes: consulting or advisory and travel reimbursement. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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