The COMT gene is notable as a candidate gene for psychosis since: it is located on chromosome 22q11, a region already implicated in schizophrenia; a microdeletion of chromosome 22q11 is associated with velo-cardio-facial syndrome (which has a high rate of psychosis); and finally, the COMT gene codes for the enzyme catechol-O-methyltransferase which is involved in the metabolism of dopamine at synapses (41). This evidence concerns the gene COMT and psychotic disorder.