This is HN, a group I would expect to have above average understanding of statistics and statistical analysis and yet the idea of causal relationships and that old adage of "correlation is not causation" STILL seems to slip past far too often.
To the larger world: There's a reason every single drug commercial/ad you've ever engaged with has a list of "possible side effect" and not "known things that will/did happen". The "possible" doesn't even always mean "this is a side effect we conclusively know this drug causes, and could possibly happen to you" but sometimes just "we couldn't prove this drug didn't cause someone to shit blood since we had one guy who did one time during our months of trials".