Many papers that reach the review stage are rejected because although their hypothesis is clear and the study is well designed, the conclusions made do not have enough data to make the case. Perhaps the sample size or patient data set is too small to yield statistically significant results.

After careful consideration by our editors, we regret to inform you that we must decline this submission on editorial grounds and subsequently have declined to send the paper out to external peer reviewers.

I think it's always best to be honest, but in a nice way. An author would request that I review their book, but I didn't like the sound of it at all. But instead of saying that, I'd say: Sorry but I'm really backed up right now and just don't have the time!

Sample peer review comments to reject a manuscript “In its current state, I do not recommend accepting this paper.” “Unfortunately, the literature review is inadequate. It lacks..” “The paper lacks a convincing theoretical framework, which is necessary to be considered for publication.”

But if you answer "no," then how can you decline to address the comment? The basic structure is simple, and based on respect: Acknowledge the reviewer's suggestion. Then state why you're not going to make the suggested change.

Declining After Accepting a Review Invitation If you initially accepted an invitation to review the paper, but decide to not review it, go to the review form linked to in the invitation email, and click the CANCEL button. See also: I agreed to review an article but realized I have a conflict of interest.

This also seems very simple: just reply on time saying that you can't do the review, and if you know someone who would be suitable, scientifically, please let editorial know :-) Should you also give an opinion on the paper that you are declining to review? Some do.