Is Schizophrenia a Progressive Neurodevelopmental Disorder? Toward a Unitary Pathogenetic Mechanism

OBJECTIVE: The author 1) reassesses the case against a neuronal degeneration hypothesis for schizophrenia; 2) demonstrates that the hypothesis that schizophrenia is a disorder caused by early (i.e., pre- or perinatal) and static (i.e., fixed, nonprogressive) damage to the brain is unsatisfactory because it cannot readily account for brain imaging results from schizophrenic patients and lacks both satisfactory clinical examples and experimental models of early, static developmental disorders resulting in the late spontaneous functional deterioration that characterizes schizophrenia; and 3) offers an alternative pathogenetic hypothesis for schizophrenia that is consistent with the available imaging and neuropathological data. METHOD: Published data on schizophrenia and relevant clinical and experimental studies of neurodevelopment and its disorders are reviewed. RESULTS: The neuropathological studies provide strong evidence against a classic neurodegenerative pathogenesis of schizophrenia and moderate support for prenatal developmental abnormalities. The imaging data provide strong evidence that excessive brain volume loss occurs after maximum brain volume expansion and equivocal evidence that it continues after onset of overt illness. The available clinical and experimental models of late deterioration after static, early brain lesions are unconvincing. A progressive developmental mechanism can reconcile the neuropathological and imaging data, while being compatible with both early onset and late deterioration. CONCLUSIONS: It matters whether the pathogenetic agent in schizophrenia is static or progressive, since if it is the latter it is worthwhile to search not only for means of prevention but also for interventions that will arrest progression as early as possible.