Who all are considered authors of papers written on behalf of a research group? In epidemiology it is not uncommon to see papers written by a bunch of authors on behalf of a research group (say "the X research group"). See, for example, this paper (randomly chosen from pubmed):


  Moreira L, Pellisé M, Carballal S, Bessa X, Ocaña T, Serradesanferm A, Grau J, Macià F, Andreu M, Castells A, Balaguer F; on behalf of the PROCOLON research group.
  High prevalence of serrated polyposis syndrome in FIT-based colorectal cancer screening programmes. Gut. 2012 Sep 14. 


My question is: are the members of the research group X (whose names and affiliations are usually reported in the Appendix at the end of the paper) considered as authors of the paper?

Edit: I am particularly interested to receive answers that apply specifically to epidemiology, but of course experiences from other fields are very welcome!
In particle physics (and we have some very long author lists) they are.

Authorship rules are generally set out in the collaboration's Memorandum of Understanding (whatever it is called) and can sometimes call for odd things such as a paper being credited to someone who didn't even know it was being written but whose work calibrating some systematic effect of a minor subsystem a decade ago was used in the paper. That happened to me once, I checked inSPIRE and discovered I had a new paper out. Turned out to be a nice one, too.

To avoid that many of these documents have a "recent membership" type of clause so that you have to have been an active member of the collaboration in the last (typically) year to be credited. "Active" is defined by things like sitting shifts, attending collaboration meetings, contributing institutional funds to the general pool or hardware to the experiment and so on.