This is a spin-off. It seems pretty basic to me, but people are actually arguing over it, so here goes:
If you state something as a fact (stats, names, studies etc) cite it.
If you are discussing ideas as opposed to debating, skip the citing if you like. Just be clear this is an idea and not a fact.
Lots of us repeat the same studies over and over again. It does get a little tiresome (I shoud bookmark the CDC pinkbook…..) - but so what? It is the price of playing and good for any newbie/lurkers.