Speaking as someone who has suffered delusions, I feel it's a myth that any particular kinds of thought can lead to madness or more precisely to any psychotic illness. Medicine isn't fully clear yet on the causes of schizophrenia, psychotic depression or other kinds of delusional illnesses, but the evidence suggests that the causes aren't really what you think. My personal experience backs this up since when I contracted schizophrenia I was busy doing a physics degree and not thinking any recursive thoughts. Unfortunately mental illness as a subject is very laden with myths which are backed up by films, the media and people generally, This "slippery slope" idea where a person looks into dangerous aspects of reality and then slowly degenerates into madness is, I think, wrong. The trouble is that many of these myths are so ingrained that to consider the truth (that we don't properly understand the causality of mental illness) can almost feel counter-intuitive.