Mmm Ill jump...
Is INFP a disease, short answer no. Being an INFP merely means that you are cognitively stacked to interpret the world a certain way. As there are 16 different types of frameworks, and some are more common than others, those who verge farther away from the majority MIGHT initially be viewed initially as being a bit... cut from a different cloth. But this does not make being an INFP a disease, and I think that you know that.
Are INFPs prone to developing what we view as mental illness? Maybe. I do not really know statistics on this, but I would guess that it would be possible for INFPs to sink into a sort of physically stagnant, 'emotionally' turbulent, depression. You could get caught up in the wreckage of the world, it can be pressing, and yeah can probably lead to mental illness. But being an INFP does not cause one to be depressed just as being an ESTJ does not cause someone to be OCD. Individual experience, cognition, pretty much any other factor spewed out from the rainbows of the flipping universe, also make up who we are. There are no faulty frameworks, just those that have suffered a few to many stones.
And this is sort of an answer to your other threads. I think it is great to ask questions, and I do not like to crush that in any way, but I am uneasy with this.
There are statistics online if those are what you are looking for, but remember that while you may type as an INFP you are made up of more than the sum of stereotypes. Your MBTI is not a badge that you can wave to justify the way you are feeling or completely who you are as a person. If this is serious, and I am very doubtful that it is at this point, (and I really hope that it isn't), this perpetuation is a bit disturbing. You do not need to validate who you are. Do not detract from you. You are who you set out to be, period. Anyway, you cannot catch Fi, spread Ne, whatever. It is you and how you interact and process, and while you have an impact on the world, a disease? Really?
Just huh?