From its first descriptions, schizophrenic psychosis had a longitudinal dimension. Thomas Clouston (Clouston, 1892; Murray, 1994; Murray and Jones, 1995) recognized a syndrome of ‘developmental insanity’ in which developmental physical abnormalities were associated with early-onset psychotic phenomena, particularly in men. Kraepelin (1896) and Bleuler (1908, 1911) noted that people who developed the psychotic syndrome were often different from their peers before psychosis began. The notion that there may be psychological differences predating psychosis was initially incorporated into psychodynamic formulations of the disorder. However, during the 1980s, a new causal paradigm emerged: the ‘neurodevelopmental hypothesis’ of schizophrenia (Murray and Lewis, 1987; Weinberger, 1987), which proposed a subtle deviance in early brain development, the full adverse consequences of which were not manifest until adolescence or early adulthood. The evidence for this hypothesis has been discussed in Chapter 5.
Central to a neurodevelopmental model of schizophrenia is the identification of manifestations characterizing those at risk during childhood and adolescence – before the overt symptoms of the illness appear. We might expect people who later develop schizophrenia to show either neurological or behavioural abnormalities during childhood or adolescence.