Earlier quoted context omitted.
> I would have imagined that most people with CF already had extreme anxiety - wondering when the infection that is going to end one's life will arrive. Is it really possible that Trikafta is causing noticeably worse anxiety? There's a discussion of this in the article. Essentially, a bunch of people have said that they started experiencing extreme anxiety when they started Trikafta, and that stopping or lowering the…
Clinicians are always a day late and a dollar short. The evidence comes from these people reporting. These clinicians need a 50 million dollar grant to get that proof.
So now you have some willing participants you have to screen your initial group to filter it down to people who actually meet your recruiting criteria and consent them for your study. Finally you actually get to gather your data, if you need people to come in for sampling and have to cover their expenses.
Next you'll look at your data and realise there's some confounding effect which reduces your powers to infer anything (e.g. somehow you overrecruited a particular group and they turn out to do something which correlates with the thing you're studying). You'll cry a little and realise you need to recruit more people to have any statistical power to draw a conclusion.
tldr; medical and scientific studies are hard if you want them to actually have any validity.