The neurodevelopmental hypothesis of schizophrenia provided a valuable
framework that allowed a condition that usually presents with frank disorder
in adolescence or early adulthood to be understood at least in part as a
consequence of events occurring early in development. However, the
implications of the neurodevelopmental hypothesis for nosological
conceptions of the disorder can only now be fully appreciated. Recent
research indicates genetic overlap between schizophrenia and syndromes in
which psychopathology is manifest in childhood and that are often grouped
together as ‘neurodevelopmental disorders' such as autism-spectrum
disorders, intellectual disability and attention-deficit hyperactivity
disorder. These findings challenge the aetiological basis of current
diagnostic categories and, together with evidence for frequent comorbidity,
suggest that we should view the functional psychoses as members of a group
of related and overlapping syndromes that result in part from a combination
of genetic and environmental effects on brain development and that are
associated with specific and general impairments of cognitive function. This
has important implications for future research and for the configuration of
psychiatric services.