Conflicts of Interest in Systematic Reviews: What to Disclose and Why

Conflict of interest disclosure in a systematic review is expected practice, but it covers more ground than many first-time authors initially realize, extending beyond simply naming your own funding source to how you handle sponsorship considerations for your included primary studies as well.

Author-level conflicts of interest

The most familiar category covers your own funding source for conducting the review, any financial relationships with organizations that might benefit from a particular conclusion, and any prior professional involvement with the specific intervention or topic under review that could reasonably be seen as influencing your objectivity. PRISMA 2020 expects explicit disclosure here, following the same standards as most other biomedical and health research publishing.

Funding source for the review itself

State clearly whether your systematic review received specific funding, from whom, and whether that funder had any role in the review's design, conduct, analysis, or decision to publish. A funder with no role beyond providing financial support is a materially different disclosure than a funder who specified the research question or reviewed results before publication, and this distinction should be stated explicitly rather than left implicit.

Conflicts related to your included studies

A less commonly recognized but methodologically important dimension is whether your included primary studies themselves were industry-funded, and whether this correlates with their reported findings. Extracting and reporting each included study's funding source, where available, lets readers and lets you assess whether your pooled evidence base skews toward industry-funded research with a plausible risk of sponsorship-related bias.

Sponsorship bias as a specific, documented phenomenon

Research specifically examining this question has found that industry-funded studies of a given intervention sometimes report more favorable findings than independently funded studies of the same intervention, a well-documented phenomenon in several fields. A systematic review that extracts funding source data and examines this pattern, where feasible, adds a genuinely useful layer of critical appraisal beyond standard risk-of-bias assessment alone.

Where to place this in your risk-of-bias assessment

Some risk-of-bias frameworks include funding source and conflict of interest as an explicit consideration within their broader appraisal, while others treat it as a separate, additional extraction item to report alongside standard risk-of-bias findings rather than folded directly into the formal RoB 2 or ROBINS-I domains, which don't explicitly include this consideration in their core structure.

Team-level conflicts and independent verification

For reviews with a specific funding source or an author team with a plausible interest in a particular conclusion, having risk-of-bias assessment and data extraction conducted by team members without the specific conflict, or by an independent third party, strengthens the review's credibility considerably more than disclosure alone. Disclosure informs readers of a potential concern; independent verification of key methodological steps actively mitigates it.

Reporting using ICMJE standards

The International Committee of Medical Journal Editors' conflict of interest disclosure form is widely used and expected across health research publishing, including systematic reviews, and completing it thoroughly and honestly for every author, not just the corresponding author, is standard expected practice most journals will require before considering your manuscript.

What happens when a genuine conflict exists

Having a conflict of interest doesn't automatically disqualify a systematic review from being conducted or published -- clinical and subject-matter experts often have some prior professional connection to a well-studied intervention area, and this is normal rather than inherently disqualifying. What matters is transparent, complete disclosure, and where a conflict is substantial, additional safeguards like independent verification of key methodological steps, rather than an attempt to conceal or minimize a genuine, disclosable interest.

A practical disclosure checklist

Confirm every author's funding sources and relevant financial relationships are disclosed completely, not selectively. Confirm your review's own funding source and that funder's specific role, if any, in the review's conduct is stated explicitly. And consider, where your evidence base plausibly warrants it, extracting and reporting your included studies' own funding sources as part of your broader critical appraisal, giving readers a fuller picture of potential sponsorship-related influence throughout your entire evidence base, not just at the level of your own authorship.

A practical example of why this distinction matters

Consider a systematic review examining a specific drug's effectiveness where the majority of included trials were funded by that drug's manufacturer. Even with impeccable author-level disclosure from the review team itself, failing to note this pattern in the underlying evidence base leaves readers without an important piece of context for interpreting the pooled result, since sponsorship-related bias in the primary literature can meaningfully shape a review's conclusions regardless of how independent the reviewers conducting the synthesis actually are.

Conflicts of interest and registered protocols

Disclosing anticipated conflicts of interest at the protocol registration stage, before conducting the review, adds a further layer of transparency, since it demonstrates the potential conflict was acknowledged before results were known, rather than disclosed only once a specific, perhaps convenient, finding had already emerged. This proactive disclosure, made before results are known, carries more credibility with careful readers than the same disclosure made only after a specific finding has already come to light. Building this habit into your standard protocol development process, rather than treating conflict disclosure as a final administrative step, reflects a genuinely more transparent approach to the entire research process from its earliest stages. Teams that build this habit consistently across multiple projects tend to find disclosure becomes a routine, low-friction part of their standard workflow rather than an occasional source of last-minute uncertainty. Over time, this consistent practice also makes the broader research culture within a team or institution more genuinely transparent, benefiting every subsequent project that team undertakes together. Building this kind of transparent disclosure culture early in a team's working relationship pays dividends across every subsequent collaboration, not just the single project where the habit was first established, extending a culture of genuine transparency well beyond any single review, which is ultimately what strengthens a field's collective trust in published evidence synthesis for years to come, well beyond the immediate scope of any one specific funding cycle or publication.