If someone is a reviewer and recommends major revisions to a medical journal paper, the review can be quite lengthy. (e.g., list of 10-15 points to work on)
On the other hand, how detailed should be the rejection review. Are you expected to provide more than 2 paragraphs justification for the rejection?
Is there any study on length of reviews that reject the paper. I would guess it would be most likely under 2 paragraphs of text. Is that correct?
Short answer: I think it is very disrespectful (or not good) to reject a paper by writing one single paragraph. If a reviewer thinks that there are obvious flaws that cannot be described clearly, then the reviewer shall simply not review the paper.
The reviewer may have not understood the paper well: Personally, many times I get a first negative impression of a paper. I try then to write a summary of the paper. Then I realize that "Oh the author meant this !" or "Oh, this actually works !" -- this usually lead me to realize at the end that the paper is good.
The authors spent a lot of time writing the paper (they are looking for constructive comments most of the time): From another point of view, put yourself in the authors shoes. They have spent a lot of time (obviously) writing the paper. They are smart people (otherwise, they would have not reached this level to write a paper). Then obviously, there is something to get from them. If the reviewer thinks that this is not enough, then strong comments should be written. In any case, a reviewer should spend a relatively long period of time in each page of the paper.
The reviewer may not have treated the problem from all perspectives: Note also that - in some cases - the reviewer may have experienced the problem from one single perspective, whereas the paper attacks the problem from a different perspective. Treating a problem with a different perspective is the best way to solve the problem IMHO. It only enriches the literature.
It should be long enough that the shortcomings of the paper are immediately obvious to the editor and the authors, but not too long that it becomes your own little personal project, sucking away your valuable time.
You can't really give a generic quantitative value for the length of the rejection review — I've rejected papers with 1 paragraph when I find that the premise/assumption for the work done in the paper is fundamentally flawed and the authors have have insufficient background and/or proceeded without knowing/addressing it at all. In other words, there's no point in me saying anything more when it is clear from the second section that everything that follows in the paper is junk (and I'm not going to spend my time on junk). On the other hand, I've also written 3 page rejection reviews when I felt that the topic was good, the authors have a basic grasp of the subject, but for other reasons such as inferences from insufficient data, sloppy writing, insufficient background/literature, incorrect methodology, etc., the paper had to be rejected as is (some journals allow for a resubmission with major overhaul).
A rejection recommendation should contain a strong and clear motivaton for what is failing in the reviewed manuscript (MS). Since it is not up to the reviewer to make decisions, any review will be a recommendation to an editor. Therefore, a review of the MS should be made to point out the perceived shortcomings of the MS. A review which essentially contains only a recommendation to reject is most likely not considered by the editor since it will be unclear why such a decision should be made.
So as a reviewer you should make a normal review and point out the weaknesses of the MS.
An editor should normally make sure a MS is ready for review before sending it out for review, but mistakes may happen. I think it is fair to leave detailed comments and focus on the larger issues that you think makes the MS unpublishable.
I am not in a medical field and my experience is limited to being a reviewer for a good journal in my field (computing and information science) for the past 2 years. I am also not aware of any studies on journal reject recommendation lengths so my answer is anecdotal and personal. With this disclaimer, I would like to say that the true answer is probably, it depends.
Personally, I have always given a list of points where I have found a paper lacking and elaborated upon them in great detail. Even if the paper is really bad, i.e from the introduction itself you can make out that you are going to recommend a reject for it, I think it my duty provide as much honest and constructive feedback that I possibly can. This is because peer reviewing comes under the third pillar of the academic tripod - service (with the other two being teaching and research). Maybe its because I am not a very experienced reviewer or I only review 1-2 papers at a time or I have more time than most to devote to this. This has been my personal, limited experience. I do not think that one can generalize here.
I am sure others will weigh in on this in meaningful ways.
I would say that it is highly field dependent and also dependent on how long the manuscript itself is. A 3 page short note is going to have a longer revision/rejection comment than a 50 page monograph almost by definition.
What I've noticed is that in practice there is almost no difference between a "major revisions" and "rejection" comment except for the final recommendation by the author. The purpose of a review is supposed to be to show the author where . If a manuscript is rejected (say, because it was submitted to a journal that is not high-impact enough or contains major flaws that could theoretically be rectified), it is still very helpful to the authors to know why it is rejected so they can revise their manuscript accordingly if they plan to resubmit.
A short rejection note could also be interpreted as the reviewer could not be bothered enough to read the entire manuscript. Whereas a long rejection note shows that you read the paper and the problems are extensive enough that the manuscript cannot be salvaged through revision. The way you get around the potential downside of your most salient points potentially being lost is to put your main criticisms up front and in the first paragraph if possible.
