Neurobiology of emotion and high risk for schizophrenia: role of the amygdala and the X-chromosome.

Abnormalities in emotion processing and in structure of the amygdala have consistently been documented in schizophrenia. A major question is whether amygdala abnormalities reflect a genetic vulnerability for the disease. In the present paper, we reviewed Magnetic Resonance Imaging (MRI) studies that reported amygdala measures in several high-risk populations: subjects from the general population with subclinical schizophrenia symptoms and relatives of schizophrenia patients. In addition, we reviewed the evidence regarding Klinefelter syndrome (characterised by an additional X-chromosome), which has also been related to an increased risk for schizophrenia. Overall, the evidence points to structural abnormalities of the amygdala in individuals at increased risk for schizophrenia. Although the genetic basis of amygdala deficits remains unclear, abnormalities (of genes) on the X-chromosome might play a role as suggested by the evidence from individuals with sex chromosome aneuploidies. We propose that amygdala abnormalities are an endophenotype in schizophrenia and may account for subtle emotional processing deficits that have been described in these high-risk groups.