If the journal says a cover letter is optional—write one anyway!
A cover letter helps to draw attention to your manuscript.
Use the cover letter to:
- Give a brief summary of your study and the main findings
- Explain what your study adds to the field
- Confirm that the results have not been previously published and is not under consideration in another journal
- You may need to include funding sources or conflicts of interest (check the Author Guidelines)
- Indicate if any part of the work has previously been presented e.g. Conference abstract or poster, Conference paper to be published in conference proceedings, Data or other results reported in the media, Previous publication of preliminary results or related results, Previous publication of the same results in another language
- In all these cases, explain in the cover letter and include a copy of the previous publication; the journal editor can then assess whether the new publication is a useful addition or is redundant.
Posting of protocols or results in clinical trials registries is not usually considered to be prior publication.
Preprints (uploaded before peer review) have a doi and are permanent but are not usually considered to be prior publication.