Well you said, "The author has a hypothesis and it's looking for evidence" - that's usually the definition of the scientific method - you form some hypoothesis and then try and find evidence to test it.
So as far as I can tell, you're describing the scientific method as "bad thinking" and criticizing the author for using it. Which is certainly quite a take.
That's not the definition of the scientific method. That's more like a quote from Interstellar than how science works.
When you encounter an unexplained phenomena (such as an increase in cases of psychosis), you should observe first, then hypothesize on what is the cause.