Conflict of Interest in Peer Review: Types & Examples
What Is a Conflict of Interest in Peer Review? Types, Examples, Disclosure, and Ethical Guidelines
Peer review depends on independent scientific judgment. When a journal invites a researcher to evaluate a manuscript, the editor expects an assessment based on the study's methodology, evidence, originality, and relevance—not the reviewer's personal relationships or outside interests.
However, academic researchers often work within interconnected professional communities. They collaborate on projects, compete for grants, publish in related fields, supervise students, and maintain relationships with universities, companies, and other organizations.
These connections can sometimes create a conflict of interest in peer review.
A conflict of interest occurs when a reviewer's financial, personal, professional, intellectual, or other interests could improperly influence—or reasonably appear to influence—their assessment of a manuscript.
Importantly, having a potential conflict does not automatically mean that a reviewer has acted dishonestly.
The ethical issue is whether the relationship could compromise independent judgment and whether it has been appropriately disclosed and managed.
Organizations such as the Committee on Publication Ethics (COPE), the International Committee of Medical Journal Editors (ICMJE), and major academic publishers provide guidance on identifying and managing these situations.
This article explains the different types of peer-review conflicts of interest, common examples, when reviewers should decline an invitation, and how to disclose potential conflicts professionally.
What Is a Conflict of Interest in Peer Review?
A conflict of interest in peer review is a circumstance in which a reviewer's outside interests or relationships may interfere with an impartial evaluation of a research manuscript.
The competing interest may benefit the reviewer directly or indirectly.
For example, a reviewer may have a financial relationship with a company whose product is being evaluated in the paper.
Alternatively, the reviewer may be a recent research collaborator of one of the authors.
These relationships create concerns because the reviewer's assessment might be influenced by considerations unrelated to the quality of the research.
The influence can be positive or negative.
A reviewer might be inclined to favor the work of a close colleague.
Another reviewer might evaluate a competing research project more harshly because its findings challenge their own work.
Both situations can affect the independence of peer review.
The ICMJE emphasizes that all participants in the scholarly publication process—including authors, reviewers, and editors—must consider and disclose relationships or activities that could influence their responsibilities.
The purpose of disclosure is not to accuse researchers of wrongdoing.
It allows the editor to decide whether an independent and credible assessment is possible.
What Are the Main Types of Conflicts of Interest?
Conflicts of interest can arise in several forms.
Some are direct and easily recognizable, such as financial ownership.
Others are more subtle, including academic competition or personal relationships.
| Conflict type | Example | Possible concern |
|---|---|---|
| Financial | Reviewer owns shares in a company whose product is evaluated | Financial benefit from an editorial outcome |
| Professional | Reviewer recently coauthored a paper with an author | Favoritism or reduced independence |
| Institutional | Reviewer works in the same academic department as an author | Shared professional interests |
| Personal | Reviewer has a close friendship or family relationship with an author | Favoritism or hostility |
| Intellectual | Reviewer is strongly invested in a competing theory | Resistance to contrary evidence |
| Competitive | Reviewer is conducting a directly competing study | Personal advantage or misuse of confidential findings |
| Supervisory | Reviewer recently supervised the manuscript's author | Power relationships and loyalty |
| Editorial | Handling editor has a significant relationship with an author | Compromised manuscript decision |
These categories may overlap.
For instance, a recent collaborator could also be a close friend and joint grant holder.
The editor should consider the full circumstances rather than assigning the relationship to only one category.
1. Financial Conflicts of Interest
A financial conflict arises when a reviewer has a monetary interest that could be affected by the manuscript's findings or publication.
Examples include employment, consultancy arrangements, company ownership, patents, stock holdings, and relevant financial compensation.
Imagine a manuscript evaluating the effectiveness of a medical device.
The invited reviewer owns shares in the company manufacturing that device.
A favorable publication might benefit the company's commercial interests.
This creates a potential conflict even if the reviewer believes they can assess the research fairly.
Financial interests do not have to involve direct payments from an author.
A reviewer may have a relevant financial relationship with a competitor, industry sponsor, or organization affected by the results.
Relevant financial interests should be disclosed according to the journal's policy.
Where the conflict could compromise independence, the reviewer should decline the assignment.
2. Professional Conflicts of Interest
Professional conflicts involve relationships developed through academic or employment activities.
These may include recent research collaborations, joint publications, grant partnerships, or other ongoing professional connections.
For example, a reviewer may have coauthored several papers with one of the manuscript's authors during the preceding two years.
Although they are not listed as an author of the current submission, the recent collaboration may raise reasonable concerns about impartiality.
COPE advises reviewers not to accept assignments involving recent close collaborators, mentors, mentees, or joint grant holders.
Its guidance mentions the previous three years as an example of a recent relationship.
However, that period is not a universal eligibility rule.
Some journals establish their own timeframes or broader restrictions.
A collaboration outside the specified period may still be relevant if the professional relationship remains particularly close.
Reviewers should disclose meaningful relationships rather than assume that enough time has automatically passed.
3. Personal Conflicts of Interest
Personal conflicts arise from relationships outside formal research collaboration.
They may include family relationships, close friendships, ongoing personal disputes, or other connections that could affect independent judgment.
For example, a reviewer may be invited to evaluate a manuscript written by a close personal friend.
Even if the reviewer intends to be objective, the relationship could reasonably create concerns about favoritism.
Similarly, a reviewer involved in a serious personal dispute with an author might be unable to provide a fair evaluation.
A reviewer does not need to publicly explain sensitive personal details.
They can inform the editor confidentially that a relationship makes independent review inappropriate.
The editor can then arrange another reviewer.
4. Institutional Conflicts of Interest
Institutional conflicts occur when professional affiliations create overlapping interests.
A common example is a reviewer employed at the same university or department as the manuscript authors.
The relationship may involve institutional reputation, internal career structures, shared resources, or administrative connections.
For example, a professor may receive a manuscript submitted by another researcher in the same academic department.
Even without direct collaboration, the shared institutional setting can raise concerns about independence.
COPE advises reviewers not to accept reviews when they are currently employed at the same institution as any author.
Wiley similarly advises that reviewers working at the authors' institution should usually decline.
However, researchers from the same large organization may have varying degrees of professional interaction.
The journal's current policy determines the applicable requirements.
5. Intellectual Conflicts of Interest
An intellectual conflict may arise when a reviewer's strong commitment to a theory, hypothesis, or research approach threatens an impartial assessment.
Academic disagreement alone is not a conflict of interest.
Reviewers are expected to challenge weak arguments and critically assess scientific methods.
The problem develops when a reviewer cannot evaluate contrary evidence fairly because of their own intellectual interests.
For example, a researcher who has spent years defending a particular theory may be invited to review a study that challenges it.
That expertise may make the reviewer highly qualified.
But if the reviewer has publicly committed to rejecting competing evidence regardless of its quality, their independence may be reasonably questioned.
An intellectual conflict does not necessarily require automatic recusal.
The relevant question is whether the reviewer can provide a balanced, evidence-based assessment.
When uncertain, the reviewer should explain the concern to the editor and ask for guidance.
6. Competitive Research Conflicts
Direct research competition can create another type of conflict.
A reviewer may be preparing a manuscript that investigates almost the same research question using closely related methods.
Receiving a confidential competitor's manuscript could provide access to unpublished ideas, results, or research strategies.
For example, two research groups may independently develop similar approaches to detecting electrical grid faults.
One group submits its findings first.
A researcher from the competing group receives an invitation to review the manuscript.
If the research is directly competitive, the reviewer may face conflicting interests involving priority, publication timing, or future research opportunities.
COPE specifically advises reviewers not to accept a manuscript solely to gain access to the work or to review a paper closely resembling research they are preparing or submitting elsewhere.
The reviewer should declare the competing interest and decline when appropriate.
Confidential research must never be used for personal or professional advantage.
7. Supervisory and Mentoring Conflicts
A reviewer may have previously supervised, mentored, or been supervised by one of the authors.
These relationships can remain professionally significant even after the formal arrangement ends.
For example, a professor might receive a manuscript written by a PhD student they supervised recently.
The professor may have a strong professional or personal interest in the student's success.
This creates a potential conflict even if the professor is not a coauthor.
COPE advises reviewers not to accept assignments involving recent mentors or mentees, using a three-year period as an example of a recent relationship.
Older relationships can also require disclosure where ongoing contact or professional dependence remains significant.
8. Editorial Conflicts of Interest
Conflicts of interest are not limited to external reviewers.
Editors may also have relationships that affect manuscript decisions.
For example, a handling editor may be invited to oversee a manuscript written by a close collaborator.
An editor may also hold relevant financial interests or be in direct competition with the authors.
Wiley's Editor Code of Conduct states that editors should disclose potential financial and nonfinancial interests that may affect their impartiality.
When a conflict exists, the editor should recuse themselves and transfer responsibility to another qualified editor.
This helps protect the independence of both reviewer selection and the final publication decision.
Conflict of Interest in Peer Review: Practical Examples
Consider the following hypothetical situations.
| Scenario | Potential conflict? | Recommended response |
|---|---|---|
| Reviewer and author work in the same department | Yes | Decline under COPE guidance and relevant journal rules |
| Reviewer recently coauthored with an author | Yes | Disclose and generally decline |
| Reviewer owns a relevant company | Yes | Disclose; decline if impartiality is compromised |
| Reviewer has never worked with the authors but studies the same field | Not necessarily | Review if qualified and otherwise independent |
| Reviewer disagrees with the manuscript's theory | Not automatically | Evaluate evidence fairly; disclose serious intellectual conflicts |
| Reviewer has a close personal friendship with an author | Yes | Decline |
| Reviewer wrote an unrelated paper with an author many years ago | Depends | Disclose if the relationship remains relevant |
| Reviewer is conducting directly competing research | Potentially serious | Disclose and decline where independence or confidentiality is at risk |
| Reviewer recognizes an author in double-anonymous review | Depends | Disclose if recognition creates a potential conflict |
| Editor has a financial interest in the outcome | Yes | Disclose and recuse |
These examples are illustrative.
The journal's conflict-of-interest policy and the specifics of the relationship determine the appropriate handling.
What Is the Difference Between an Actual, Potential, and Perceived Conflict?
Conflicts are sometimes described using three categories.
Actual conflict: A competing interest exists and is directly relevant to the reviewer's responsibilities.
Potential conflict: An existing relationship or interest could compromise judgment under the circumstances.
Perceived conflict: A reasonable observer might question the reviewer's independence, even if the reviewer believes they can remain impartial.
For example, imagine a reviewer whose spouse works for a company affected by the research.
The reviewer may believe that the relationship would not change their scientific judgment.
Nevertheless, a reasonable observer could question whether the connection creates competing interests.
Disclosure enables the editor to decide how to handle that concern.
The purpose is to maintain confidence in the fairness of the process.
Is a Conflict of Interest the Same as Reviewer Bias?
No.
A conflict of interest and reviewer bias are related but distinct.
Conflict of interest concerns relationships, commitments, or incentives that may compromise independence.
Reviewer bias concerns influences that distort judgment.
A reviewer may have a financial conflict but still prepare a scientifically accurate report.
Conversely, a reviewer may have no identifiable financial or professional conflict yet unconsciously favor a particular methodology.
| Feature | Conflict of interest | Reviewer bias |
|---|---|---|
| Main concern | Competing relationships or interests | Distorted judgment |
| Requires proven unfair behavior | No | Bias may appear through decisions or assessments |
| May exist without awareness | Yes | Yes |
| Common management | Disclosure and possible recusal | Review training, structured assessment, oversight |
| Example | Reviewing a close collaborator's paper | Unfairly favoring a prestigious institution |
A conflict does not prove biased conduct.
However, conflict management reduces circumstances in which bias may arise or reasonably be suspected.
When Should a Peer Reviewer Decline an Invitation?
Reviewers should decline when they cannot provide an independent assessment because of a relevant conflict.
COPE identifies several situations in which reviewers should not agree to review.
These include current employment at the same institution as an author and recent close mentoring, collaboration, or joint grant relationships.
A reviewer should also decline when they have a directly competing manuscript or intend to use the unpublished submission for personal advantage.
Other circumstances may require discussion with the editor.
For example, a distant professional relationship may not automatically make reviewing inappropriate.
The reviewer should disclose it and allow the editor to determine whether participation is permitted.
If a conflict clearly prevents fair evaluation, declining is preferable to accepting and simply adding a disclosure statement.
How to Disclose a Conflict of Interest to a Journal
Disclosure should occur before the reviewer accepts an assignment whenever the relevant information is known.
A practical process involves the following steps.
Step 1: Read the Journal's Policy
Check the journal's requirements concerning coauthorship, employment, funding, personal relationships, and academic competition.
Step 2: Identify Relevant Relationships
Consider current and recent professional connections, financial interests, mentoring arrangements, competing research, and significant personal relationships.
Step 3: Evaluate Whether Independence Is Possible
Ask whether the interest could reasonably influence the review or create doubts about its impartiality.
Step 4: Notify the Editor
Describe the relevant relationship accurately and concisely.
For minor or uncertain concerns, request guidance.
Step 5: Follow the Editor's Decision
The editor may determine that the relationship does not prevent review, request additional information, or assign another reviewer.
Step 6: Report Newly Discovered Conflicts
If an important conflict becomes apparent after the review has begun, inform the editor promptly.
Do not continue as though the concern did not exist.
Step 7: Preserve Confidentiality
Conflict disclosure does not authorize sharing the manuscript or the review invitation publicly.
Use the journal's designated communication channels.
Conflict of Interest Disclosure Examples
The following examples can be adapted to genuine situations.
Example 1: Recent Collaboration
Situation: The reviewer coauthored an article with one of the manuscript authors last year.
Suggested disclosure:
"I recently coauthored a publication with one of the manuscript's authors. Because this professional relationship may affect the independence of my assessment, I should decline the invitation."
Example 2: Potential Financial Conflict
Situation: The reviewer has a consultancy relationship with a company whose technology is directly evaluated.
Suggested disclosure:
"I have an ongoing consultancy relationship with a company whose technology is relevant to the submitted study. I am disclosing this interest before accepting the review so that the editorial office can determine the appropriate course of action."
If the interest clearly compromises independence, the reviewer should decline rather than wait for authorization.
Example 3: Older Professional Relationship
Situation: The reviewer collaborated with an author many years ago but has had no recent professional contact.
Suggested disclosure:
"I previously collaborated with one of the authors, although our last joint project concluded several years ago. We have no current research or financial relationship. Please advise whether this history affects my eligibility to review."
Example 4: Directly Competing Research
Situation: The reviewer is preparing a closely related manuscript.
Suggested disclosure:
"My research team is currently preparing a study that addresses a closely related question. To avoid a potential conflict involving unpublished competing work, I must decline this review invitation."
Example 5: No Relevant Conflict
Situation: The reviewer has considered the journal's criteria and identified no relevant competing interests.
Suggested statement:
"To the best of my knowledge, I have no financial, professional, personal, or other competing interests relevant to this manuscript."
Such a declaration should only be made after considering the actual circumstances.
Can a Reviewer Continue After Disclosing a Conflict?
Sometimes, but not always.
Disclosure allows the editor to assess the circumstances.
A minor or remote professional connection may be manageable under a particular journal's policy.
However, certain relationships are sufficiently significant that the reviewer should decline.
For example, COPE advises against reviewing manuscripts from authors at the same institution or involving recent close collaborators.
An editor should not assume that simply recording a conflict makes an otherwise inappropriate review acceptable.
Disclosure and recusal serve different purposes.
Disclosure identifies the interest.
Recusal removes the person from an evaluation they should not conduct.
What Happens if a Reviewer Discovers a Conflict During Review?
A reviewer may begin an assignment without recognizing a potential conflict.
For example, in double-anonymous peer review, author identities are initially concealed.
The reviewer may later recognize a research group through a distinctive dataset or reference.
If that recognition reveals a relevant personal or professional relationship, the reviewer should notify the editor promptly.
COPE recommends seeking editorial guidance if a conflict becomes apparent during review and refraining from further assessment while the issue is being resolved.
The journal may assign another reviewer or determine another appropriate course of action.
The reviewer should not contact the authors independently about the manuscript.
Does Working in the Same Research Field Create a Conflict?
Not automatically.
Scientific peer review requires subject expertise.
Researchers who specialize in the same field often know one another's published work.
For example, two electrical engineers may independently study renewable energy integration.
That shared research interest alone does not prevent one from reviewing the other's manuscript.
A conflict becomes more likely when additional circumstances exist, such as direct competition, close collaboration, personal relationships, or an interest in the publication outcome.
Reviewers should distinguish ordinary disciplinary expertise from competing interests that could affect independence.
Can Authors Recommend Reviewers They Know?
Some journals permit authors to suggest qualified reviewers.
However, suggested reviewers must satisfy the journal's independence and conflict-of-interest requirements.
A researcher should not recommend a close collaborator while concealing the relationship.
Likewise, authors should not provide misleading contact details or attempt to influence the evaluation through inappropriate relationships.
Editors remain responsible for reviewer selection and verification.
Legitimate reviewer suggestions are not inherently unethical.
The problem arises when the recommendation undermines independent scientific review.
What Responsibilities Do Journal Editors Have?
Editors play a central role in managing conflicts of interest.
According to Wiley's guidance, journals should establish clear procedures for obtaining and evaluating relevant disclosures.
Editors should assess conflicts when assigning reviewers and handling manuscripts.
They must also consider their own financial, personal, and professional interests.
When the editor handling a submission has a significant conflict, responsibility should be transferred to another appropriate editor.
A credible editorial process should include:
- Clear written conflict-of-interest policies.
- Reviewer disclosure requirements.
- Checks for recent collaborations and shared affiliations where practicable.
- Confidential procedures for sensitive disclosures.
- Appropriate recusal decisions.
- Documented handling of concerns.
- Escalation procedures for suspected nondisclosure or misconduct.
Managing conflicts protects both the scientific record and the researchers participating in peer review.
What Happens if a Reviewer Fails to Disclose a Conflict?
The consequences depend on the seriousness of the relationship and whether the nondisclosure was intentional.
An overlooked minor connection may be addressed through clarification.
A significant concealed relationship may require the journal to disregard the existing report or commission an independent replacement review.
If the nondisclosure involves deliberate deception or manipulation, a formal research-integrity investigation may be appropriate.
JMIR Publications warns that undisclosed conflicts may lead to exclusion of the affected review report from editorial consideration and other action consistent with publishing-ethics guidance.
A conflict discovered after publication may require the journal to examine whether the article's evaluation was compromised.
However, the presence of a conflict does not automatically justify retraction.
The publisher must assess the evidence and the effect on the integrity of the editorial process.
Conflict of Interest vs. Peer Review Manipulation
These concepts should not be treated as interchangeable.
A conflict of interest can arise naturally from legitimate academic or professional relationships.
Peer review manipulation involves intentional dishonest interference with manuscript evaluation.
For example, a professor invited to review a former student's manuscript may have a conflict even if no dishonest conduct occurs.
If that professor conceals the relationship and participates in a coordinated scheme to secure publication, the situation could involve manipulation as well.
The distinction matters because responses should be proportionate.
Conflict management generally involves disclosure, editorial assessment, and recusal when necessary.
Manipulation may require investigation, corrective action, and potential sanctions.
Peer Reviewer Conflict of Interest Checklist
Before accepting a manuscript review, consider the following questions.
| Question | Action if yes |
|---|---|
| Do I work at the same institution as an author? | Decline under COPE guidance |
| Have I recently coauthored with an author? | Disclose and generally decline |
| Have I recently supervised or been supervised by an author? | Disclose and generally decline |
| Do I share a current grant or project with an author? | Disclose and decline where relevant |
| Do I have a financial interest connected with the findings? | Disclose and assess whether recusal is necessary |
| Do I have a close personal relationship with an author? | Decline if independence is affected |
| Am I preparing directly competing research? | Disclose and decline when the work is closely related |
| Could I benefit professionally from delaying the manuscript? | Decline |
| Do I have a strong intellectual commitment that may prevent fair assessment? | Seek editorial guidance |
| Am I unsure whether a relationship counts as a conflict? | Ask the editor before proceeding |
The checklist is a practical aid and does not replace the journal's current requirements.
Frequently Asked Questions About Conflicts of Interest in Peer Review
What is a conflict of interest in peer review?
A conflict of interest occurs when a reviewer's financial, professional, personal, intellectual, or other interests could compromise—or reasonably appear to compromise—the independence of their manuscript assessment.
What are examples of reviewer conflicts of interest?
Examples include recent coauthorship with an author, employment at the same institution, close personal relationships, relevant financial interests, direct research competition, and recent mentoring relationships.
Should I decline a review if I know the author?
It depends on the relationship. Knowing an author's published research is not automatically a conflict. Close collaboration, personal relationships, and other significant interests may require declining.
Can I review a paper from my own university?
COPE advises reviewers not to accept reviews of manuscripts authored by researchers at their current institution. Follow the journal's specific policy as well.
How far back does a coauthorship conflict extend?
COPE refers to the previous three years as an example of a recent close collaboration. Journals may use different periods, and older relationships can still require disclosure if they remain significant.
Is a financial conflict always disqualifying?
Not every financial relationship has the same relevance. However, interests that could compromise independent judgment may require recusal. The relationship should be disclosed and assessed under journal policy.
What should I write in a conflict-of-interest declaration?
State the relevant relationship or interest accurately and explain its connection to the manuscript. If no relevant conflict exists, use the journal's required declaration wording.
Can a reviewer continue after disclosing a conflict?
In some cases, an editor may determine that a limited or remote interest is manageable. More significant conflicts require declining or recusal.
What if I discover a conflict after accepting the review?
Notify the editor immediately and seek instructions. Do not continue reviewing until the situation has been appropriately addressed.
Is reviewer bias the same as a conflict of interest?
No. A conflict involves competing relationships or interests, while bias concerns influences that distort judgment. A conflict can exist without proven bias.
Can editors have conflicts of interest?
Yes. Editors can have financial, professional, or personal relationships that affect independence. They should disclose such interests and recuse themselves when appropriate.
Can an undisclosed conflict lead to retraction?
It may contribute to an investigation if the publication process was seriously compromised. Retraction is not automatic and depends on the evidence and applicable editorial guidance.
Conclusion
A conflict of interest in peer review arises when a reviewer's outside relationships or interests may compromise the independence of their scientific assessment.
Financial arrangements, recent academic collaborations, personal relationships, institutional connections, intellectual commitments, and directly competing research can all create potential concerns.
Importantly, a conflict does not automatically indicate misconduct.
The central ethical responsibility is to recognize relevant interests, disclose them promptly, and decline reviewing when impartial evaluation cannot be assured.
COPE, ICMJE, and major publishers emphasize that reviewers, editors, and authors all share responsibility for transparent conflict management.
By applying clear disclosure policies, appropriate recusal, and independent reviewer selection, journals can strengthen trust in the scientific evaluation process.
Independent peer review does not require researchers to have no professional relationships. It requires those relationships to be managed so that scientific judgment remains credible and fair.