Earlier quoted context omitted.
Nonsense. I don’t know any researcher that likes sacrificing animals though every single one is painfully aware of the moral weight. They also go out of their way to minimize suffering, for ethical reasons, for selfish reasons, and even to improve the quality of the data. The reason I jumped down the parent's throat is because it reinforces the mistaken idea that scientists are okay with “moderately barbaric” things…
I'll grant that most of them don't like it, but there's a far too high fraction that uses animals even though they do not need to. This is a constant and ongoing point of contention between animal rights groups and large biologically-focused universities. Generally it comes down to budgeting concerns (ie it is cheaper to use animals) or time concerns (ie it is faster to use animals). Whether or not one of those two a…
My impression is that animal work is literally never the cheap or fast option. It's slow, it's labor-intensive, and it's expensive, while career incentives favor doing things that are quick and cheap.
It's certainly true that someone could have run a version of this study where patients with depression were "prescribed" different doses of caffeine and asked to fill out rating scales to quantify its effects on their symptoms. This experiment could reveal its effect on symptoms, the headline of this article, but it wouldn't suffice for understanding the pharmacological mechanisms (see Table 4). I don't think there are PET ligands available for any of those metabolites, and even if there were (and ignoring the animal work needed to develop them), injecting people with radioactive tracers also raises ethical questions.