Dr. Emily Deans reviews the evidence at her blog. Here’s the conventional explanation of schizophrenia from UpToDate.com:
“Although the pathogenesis [cause] of the disorder is unknown, it is almost certain that schizophrenia represents a syndrome comprised of multiple diseases that present with similar signs and symptoms. This heterogeneity complicates the elucidation of the etiological and pathophysiological factors that underlie the group of disorders. Schizophrenia appears to be a uniquely human condition, which limits the utility of animal models. There is little doubt that schizophrenia proceeds from a complex interaction between genes and the environment, but even the attempt to differentiate genetic from environment risk factors may be artificial, since environmental factors can influence gene expression just as a person’s genetic make-up can influence response to environmental stressors.”
Paleo Diabetic 