Significant clinical and laboratory differences have been reported between schizophrenic patients with large and small ventricular size. If large ventricles are a marker for a distinct subtype of schizophrenia, then the large ventricles might be expected to form a distinct cluster apart from the main body of values. In order to assess this question of unimodality versus bimodality of ventricular size in schizophrenia we reviewed all published English language VBR studies in which individual data points were available (schizophrenics: n=691, medical controls: n=205, unselected volunteers: n=16)). We plotted the frequency distribution of raw VBRs, Z-transformed VBRs, and VBRs transformed utilizing the group mean for the volunteers to correct for small inter-study differences in measurement technique. In each case distributions were unimodal skewed to the right for schizophrenic patients. These results do not support the notion of bimodality of ventricular size in schizophrenia. The mean raw VBR for schizophrenic patients (mean = 6.75) was significantly larger (F = 82.5, p < .0001) than that of medical controls (mean = 3.90) and unselected volunteers (mean = 3.79).
