A cohort study: A is causing B __OR__ A is causing B: a cohort study
Most research titles are written as the second example. Would it be correct to use the first structure?
A population-wide cohort study: A is causing B
A is causing B: a population-wide cohort study
This site tries to avoid mere opinion, so rather than give an opinion on “correctness”, it may be helpful to analyse the difference of implication between such titles, typical of some research papers.
The first is ”A general theme: illustrated by a case study”
The second is ”A case study: an example of a general theme”
Because the paper describes research that was done to generate the case study, the author’s focus is usually on the case study. This accounts for the predominance of the second title, emphasising the case study before its general context.
If the paper is written from the standpoint of the general theme and sees the case study as contributing to the corpus of knowledge on that theme, the author may be more likely to use the first title.
I there suggest that either may confidently be used, leaving these minor implications to be assimilated or not by the reader. The relation of the specific case study to the general context will be clear in the body of the paper.