[mewse]

As a practical matter, studies about links between major diseases will always always be talking about correlation.

To reach 'causation' would require intentionally giving your experimental subjects Covid-19 (and in a way that didn't result in them knowing they'd had it!), and that's unlikely to pass muster with the ethics review board.

[jcoletti]

Hm, I thought other methods could be used to establish causation, such as longitudinal cohorts, RCTs, and (another randomization I'm forgetting), that wouldn't require infecting humans, but maybe I'm confusing these