Brain growth and the age at onset of schizophrenia. The end of head and brain growth, presumably associated with a decline in growth factors, marks the beginning of the age of onset in schizophrenia. Data from [2, 207]. The growth curve is supported by results from developmental studies of brain metabolism and of brain volume [10, 208]. In addition, several studies have reported smaller head size at birth in individuals who later developed schizophrenia compared to controls (for review ).