Schizophrenia is not a karmic matter. It is an organic disease just as much as cancer is. I don’t see how anything someone did in a previous life, or early in their current life, would bring this horrible thing on them. Anybody can develop this condition at any time, although it usually starts in young adulthood.
I gather we are both familiar with this disease.
It’s a mistake to condemn a person on the basis of his or her lot, and also can be highly misleading to say she or he “deserves” it.