Brain maturational processes and delayed onset in schizophrenia.

The central feature of schizophrenia is its onset in adolescence. Although this clinical observation is consistent with the view that schizophrenia may be a neurodevelopmental disorder, debate has focused on when the proposed brain maturational deviations may begin and what might be the nature of such defective development. Conflicting models of this illness (e.g., the early and late neurodevelopmental models) have been proposed. In this paper, we will first review concepts from basic developmental neurobiology pertinent to these issues; we then summarize aspects of the neurobiology of schizophrenia that have a particular bearing on the adolescent onset of this illness. We propose that the schizophrenic syndrome may result from early brain adversity and late maturational processes of brain development interacting with adverse humoral, biochemical, and psychosocial factors during adolescence and early adulthood. The onset of schizophrenia in adolescence may be related to the "plasticity switch" secondary to the peripubertal brain maturational changes, perhaps involving an alteration in glutamate receptor function. This loss of plasticity could result in social and nonsocial cognitive deficits that are central to the pathophysiology of schizophrenia; the vulnerable person may therefore utilize prepubertal processing styles that are insufficient to the adaptive and "gistful" abstraction requirements of adult cognition. Schizophrenia onset might occur in the context of psychosocial developmental challenges to a delayed social cognitive capacity among neurodevelopmentally compromised individuals. We review therapeutic implications as well as testable predictions generated by this model, and discuss research strategies that might further our understanding of the brain maturational abnormalities in schizophrenia.