Other evidence suggest that the theory may apply only to those schizophrenics with positive symptoms. More recent developments recognizing differences among the neural pathways that use dopamine as a transmitter may account for the simultaneous presence of positive and negative symptoms in a schizophrenic patient. To date, the excess dopamine hypothesis, while promising, has not been proven conclusively. Autopsy studies indicate structural problems in limbic areas, the diencephalon, and the prefrontal cortex. CAT scan and MRI studies reveal enlarged ventricles, suggesting a deterioration or atrophy of brain tissue.
PET scans suggest atrophy in the prefrontal areas.
Some evidence supports the hypothesis that a viral infection occurring during the sixth month of fetal development may cause this brain damage. It has been hypothesized that this early brain injury remains silent until the prefrontal cortex matures, typically in adolescence. Psychological Stress and Schizophrenia Numerous studies have shown a relation between lower social class and schizophrenia. This correlation has been interpreted in both directions. The sociogenic hypothesis suggests that low social class causes schizophrenia, whereas the social-drift hypothesis argues that schizophrenics become poor because of their life difficulties.