Schizophrenia is a multifactorial disorder that is associated with disturbed cerebral development. Structural brain-imaging studies have consistently shown that the volumes of some parts of the brain, particularly the mesial temporal lobes, are smaller in patients with schizophrenia than in healthy people. Whether these abnormalities of brain structure predate the onset of symptoms is not known.

100 people at high risk of developing schizophrenia (two or more first-degree or second-degree relatives affected), 20 patients in their first episode of schizophrenia, and 30 healthy controls underwent magnetic resonance imaging of the brain. The volumes of regions of interest were measured by standard techniques.

Mean whole-brain volume was 1356 cm³ (SD 178) in the first-episode group, 1347 cm³ (122) in the high-risk group, and 1334 cm³ (149) in the controls (p=0·8). The mean volume of the left amygdalahippocampal complex (AHC) was lower in the first-episode group (4·3 cm³ [0·6]) than in the high-risk group (4·6 cm³ [0·6]), and in turn than in the controls (4·8 cm³ [0·7]); these differences were significant (p<0·05) both for absolute volumes and values adjusted for brain volume and other confounders. The right AHC showed a similar pattern (absolute volumes 4·5 cm³ [0·7], 4·8 cm³ [0·6], 4·9 cm³ [0·9], respectively). Both thalamic nuclei were significantly smaller in the high-risk group than in the control group.

People at high risk of developing schizophrenia for genetic reasons have several structural brain abnormalities that are similar to those in patients with the disorder. If at-risk individuals with particularly small AHC or thalami are most likely to develop schizophrenia, this feature might assist in early detection and treatment.