Medical systematic reviews sit at the top of the evidence hierarchy. They are meant to guide clinicians, policymakers, and patients by carefully summarizing what research truly shows. But what happens when the results point in one direction — and the conclusions in another?
A new CoEHAR article published in Research Integrity and Peer Review sheds light on a subtle but potentially consequential reporting pattern: review authors may report statistically significant benefits for an intervention, yet downplay, dismiss, or even recommend against its use in the final conclusions.
The authors propose a new term for this mismatch: “reverse spin bias.”
The phenomenon was first noticed while examining systematic reviews on e-cigarettes for smoking cessation — a highly debated topic where science, perception, and policy often collide.
In an analysis of 16 systematic reviews published between 2021 and 2025:
- 13 reviews reported e-cigarettes as significantly more effective than other cessation methods
- Yet only three review teams actually recommended their use
- The majority either discouraged their adoption or avoided any supportive recommendation, despite reporting clear benefits
The same pattern emerged in another controversial medical area: medical cannabis for pain. In a PubMed scoping search of systematic reviews published over the same period, 10 out of 29 reviews displayed a similar disconnect between results and recommendations.
Narrative mechanisms behind “reverse spin”
The paper outlines five recurring narrative strategies that may drive this reversal:
- Discounting the overall evidence base
- Discrediting primary studies
- Appealing to fear or precautionary framing
- Rejecting the treatment modality a priori
- Omitting or minimizing favorable findings
Together, these mechanisms can create a situation where positive results are technically reported, but their clinical meaning is effectively neutralized in the final message. CoEHAR researchers argue that editors and peer reviewers should more consistently verify a basic but often overlooked question: Do the recommendations actually align with the results presented?
In polarized areas of medicine, where interventions are socially or politically contested, this kind of bias may be especially common — and especially harmful. “Reverse spin bias” may become a useful label for cases in which systematic reviews report benefits, yet still issue negative or non-supportive recommendations. Recognizing and addressing this reporting mismatch could help ensure that medical guidance remains more consistently evidence-based.
Reference
O’Leary R, La Rosa GRM, Polosa R.
Reverse spin bias: preliminary observations of reporting bias in medical systematic reviews.
Research Integrity and Peer Review. 2026 Jan 9;11(1):1.
DOI: 10.1186/s41073-025-00185-9.
PMID: 41508049.
Link: https://link.springer.com/article/10.1186/s41073-025-00185-9
