Scientists from the US National Institute of Mental Health (NIMH) have found a gene variation that may increase the risk of developing schizophrenia. The gene, called COMT (catechol-o-methytransferase) appears to control levels of the chemical dopamine in the brain. Lower levels of dopamine can affect performance in memory tasks and increase the risk of developing the disease.
The NIMH researchers studied people with schizophrenia and their siblings who did not have the disease. All participants had their DNA analysed for the presence or absence of the variation. Previous studies have assumed schizophrenia to be 80 per cent heritable, and some chromosome regions have been linked to this, but as yet no genetic link has been definitely confirmed. This study hopes to be the first to identify a gene which might be implicated in conferring susceptibility to schizophrenia, but must be verified by independent researchers.
The COMT gene codes for an enzyme that breaks down dopamine. Children inherit two copies of the gene, one from either parent, but it has two forms. The more common 'val' variant reduces dopamine levels, and the less common 'met' increases it. The people studied performed memory tests, and it was found that those with two copies of the 'val' gene performed worse than those with only one or no copies. By studying the parents it was found that the 'val' COMT gene was passed on to offspring who later became schizophrenic more often than would normally be expected.