The brain (neurons, minicolumns, columns, modules, regions, hemispheres) functions by the adversarial (competitive) composition for coherence (overlapping, matching), resulting in the seizure of attention (victory) by the Thalamus (control of attention by the persistence of feedback across the neocortex), which causes recursion( persistence of context).
Any sufficiently widespread degeneration of that consolidation into coherence (severely in the hippocampal region, generally across the neocortex), will cause the failure of that recursion.
The brain functions by continuous iterations of recursive disambiguation held by the thalamus(auto-associative attention) and anterior (front) cingulate cortext (recursive attention) the prefrontal cortex(goal intention).
That’s why language (grammar) is organized as continuous recursive disambiguation: pathfinding. So schizophrenia and all its symptoms in all their forms and severities are easily explicable as general degenerative disorder – most critically of the thalamus -> cingulate cortex -> prefrontal cortex.
And even that sequence may simply be the most severe of a spectrum of disorders. So just as Alzheimer’s begins in the hippocampal region preventing the formation of memories, and resulting in the degeneration of memories (sort of top-down failure of the brain), schizophrenia affects the other end of the spectrum (the bottom-up failure of the brain) by the degeneration of control competition for coherence and therefore attention, causing degeneration in the hierarchy of recursion of associations. This is why the initial association formed in the neocortex appears to function but the recursion upon that association fails.
I have no idea other than the apparent causal, hierarchical, sequence of depression to schizophrenia hints at some relation to immunological disorders, viral disorders, and developmental disorders – even that is just a suspicion, but the current research certainly takes that position.
( This exposition is a reason why you want to understand my work on the operational explanation of the function of the brain. )