Is schizophrenia the price of human central nervous system complexity?

The purpose of the present study was to determine if there is evidence to support the hypothesis that schizophrenia is a human-specific disorder associated with the need for highly complex central nervous system (CNS) development. A review was therefore undertaken of published literature relevant to the identification of human-specific CNS development. There was no clear evidence found at the macroscopic, microscopic or molecular level that suggests unique changes have occurred in the evolution of the human CNS. Rather, highly significant changes in the size of the frontal lobe, increases in numbers of specific cell types, changes in gene expression and changes in genome sequence all seem to be involved in the evolution of the human CNS. Human-specific changes in CNS development are wide ranging. The modification in CNS structure and function that has resulted from these changes affects many pathways and behaviours that appear to be also affected in subjects with schizophrenia. Therefore there is evidence to support the hypothesis that schizophrenia is a disease that develops because of derangements to human-specific CNS functions that have emerged since our species diverged from non-human primates.