My position is pretty much as I posted in the earlier topic:
As far as I can tell, Fischer came from such a bizarre, chaotic situation, he came by his psychological problems -- especially paranoia -- honestly.
Fischer grew up fatherless and in near-poverty. His mother was an intelligent, ex-medical student, who studied in Moscow but returned to the US then moved her family around the country trying to make ends meet. She was also a communist and a political activist. The FBI investigated both Fischer and his mother as possible communist agents. Interestingly, she was diagnosed with a paranoid personality disorder after a court-ordered psychiatric exam.
Although Fischer's mother was cleared by the FBI -- after accumulating a 750 page file -- I wouldn't be surprised if she did work for the Soviets in some capacity. Somehow she completed her medical training in East Berlin in the sixties.
Fischer dropped out of school and broke up with his mother while a teenager. After that it was just Fischer and chess plus a handful of supporters. As he grew to be one of the strongest players in the world, the Soviet chess establishment was indeed conspiring against him.
After he won the world championship, he became a world famous celebrity with all the hassles and manipulations that go with fame and for which Fischer had no defenses except to retreat into seclusion. Many people have been broken by fame.
Fischer had almost no personal resources beyond what he could achieve over a chess board. As world champion, he had nowhere to go but down.
Rightly or wrongly, I think of mad people as people with hroken brains. Just as your pancreas can stop working properly and you become diabetic, your brain can stop working and you become schizophrenic or something else.
In that sense, I don't believe Fischer was mad. The stress of his childhood, the struggle to single-handedly defeat the Soviet chess machine, and the challenges of fame, broke this young man into a sad, bitter, paranoid adult.
There is more to say about Robert J. Fischer than the previous topic about Frank Brady easily allows.
Perhaps we can continue a broader, more sensible conversation here.