Cognitive deficits in treatment-resistant depression: protocol for a systematic review and meta-analysis
Bibliographic record
Abstract
INTRODUCTION: Major depressive disorder (MDD) is a major global healthcare challenge. This is, in part, due to the lack of treatment response and chronic course of MDD. Such a course of illness is often termed treatment-resistant depression (TRD) and is seen in over one-third of people with MDD. Reasons for treatment resistance are not well established, nor is the definition of TRD. Duration and severity of depression, however, are associated with TRD and are also associated with cognitive deficits. Thus, TRD could be particularly prone to cognitive deficits and at heightened risk for neuroprogression. While the cognitive profile of MDD has been investigated in several systematic reviews, no systematic review of cognition in TRD exists to date. The present study will fill this gap in the literature. It is expected that TRD will show more severe cognitive deficits than generally reported in MDD and deficits in all cognitive functions are expected. METHODS AND ANALYSIS: A systematic review following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines will be performed of the databases Embase, Pubmed/MEDLINE, PsychINFO and Cochrane including peer-reviewed studies on humans using standardised cognitive tests. Pilot searching was performed in January 2025 and the full search will be commenced in June 2025, with additional searches following completion. Where sufficient data are reported, a meta-analysis comparing deficits in TRD with MDD and healthy control participants will be performed; alternatively, effects based on norms will be calculated. Meta-regression, subgroup and sensitivity analyses will be conducted to explore moderators that are sufficiently reported in the literature. The quality of studies will be assessed by the Newcastle-Ottawa Scale. ETHICS AND DISSEMINATION: Ethical approval is not necessary to perform the study, and results will be presented at a suitable conference and published in a peer-reviewed journal. PROSPERO REGISTRATION NUMBER: CRD42024538898.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.062 | 0.079 |
| Meta-epidemiology (narrow) | 0.006 | 0.005 |
| Meta-epidemiology (broad) | 0.025 | 0.036 |
| Bibliometrics | 0.010 | 0.010 |
| Science and technology studies | 0.003 | 0.003 |
| Scholarly communication | 0.007 | 0.007 |
| Open science | 0.005 | 0.005 |
| Research integrity | 0.006 | 0.007 |
| Insufficient payload (model declined to judge) | 0.070 | 0.007 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".