Progressive changes in the development toward schizophrenia:: Studies in subjects at increased symptomatic risk

Although the underlying neurobiology of emerging psychotic disorders is not well understood, there is a growing conviction that the study of patients at clinical high risk for the illness will provide important insights. Further, a better understanding of the transition period may help the development of novel therapies. In this review, we summarize the extant neuroimaging and neuropsychological studies of people at clinical high risk for psychosis. By and large, there are few definitive markers that distinguish those who go on to develop the illness from those who do not. The 2 most consistently abnormal brain regions in schizophrenia research, the hippocampi and the lateral ventricles, are not significantly different from healthy controls prior to psychosis onset. However, frontal lobe measures (eg, cortical thickness in the anterior cingulate) do show promise, as do cognitive measures sensitive to prefrontal cortex dysfunction. Further, longitudinal magnetic resonance imaging findings in individuals at ultrahigh risk for developing a psychotic illness show that there are excessive neuroanatomical changes in those who convert to psychosis. These aberrant changes are observed most prominently in medial temporal and prefrontal cortical regions. While the pathological processes underlying such changes remain unclear, speculatively they may reflect anomalies in genetic and/or other endogenous mechanisms responsible for brain maturation, the adverse effects of intense or prolonged stress, or other environmental factors. Active changes during transition to illness may present the potential to intervene and ameliorate these changes with potential benefit clinically.