Why do mental illnesses happen?

I was always (not quite right-according to parent) but I did fine in school -
but at about age 16 I came down with a bad viral infection and including pneumonia. My world started to get weird after that -visual hallucinations and ghostly things–but it wasn’t until age 20 that I had my first actual breakdown where I couldn’t function.
But after being treated for depression for a couple years I was back into the world with a career.
Fine more or less with occasional ghostly visitors and annoying voices until age 46 and bam big breakdown again. I hope there are not any others.
I dont think my experience is typical for schizophrenia but thats my diagnosis for the past 8 years.
Also I dont take meds as per my Drs advice due to sensitivity to meds–I know I am not typical and I still wonder if they have my diagnosis wrong.

how about cultural interpretations? does it matter?

Why do people go crazy? All kinds of reasons, imagine what might drive a person out of their minds, there are so many ways, so many circumstances, especially the world being the way it is. Biological cause…yeah that’s so simple to deal with ain’t it? Of course there’s evidence there? Does it exclude all other evidedence in other areas? OF course not but ya can’t go up against the big guy’s they kill ya.