BackgroundGrey matter and other structural brain abnormalities are consistently reported in first-onset schizophrenia, but less is known about the extent of neuroanatomical changes in first-onset affective psychosisAimsTo determine which brain abnormalities are specific to (a) schizophrenia and (b) affective psychosisMethodWe obtained dual-echo (proton density/T2-weighted) magnetic resonance images and carried out voxel-based analysis on the images of 73 patients with first-episode psychosis (schizophrenia n=44, affective psychosis n=29) and 58 healthy controlsResultsBoth patients with schizophrenia and patients with affective psychosis had enlarged lateral and third ventricle volumes. Regional cortical grey matter reductions (including bilateral anterior cingulate gyrus, left insula and left fusiform gyrus) were evident in affective psychosis but not in schizophrenia, although patients with schizophrenia displayed decreased hippocampal grey matter and increased striatal grey matter at a more liberal statistical thresholdConclusionsBoth schizophrenia and affective psychosis are associated with volumetric abnormalities at the onset of frank psychosis, with some of these evident in common brain areas