Faulty gene may identify those at risk of schizophrenia

Oct 24 2005

Scientists believe they have discovered a genetic defect which could help explain the biological basis of schizophrenia.

Schizophrenia is the most common severe mental illness in Britain, and the findings could result in earlier diagnosis in children and young people, and lead to the development of new drugs and better treatment.

A study by scientists at Stanford University in California, has found that a genetic defect in some people can trigger a dangerous increase in levels of a natural brain chemical called dopamine, which may lead to schizophrenia.

At present they think the discovery probably only applies to a small proportion of people who develop the illness, but the scientists believe it could result in a fundamental change in the understanding of the condition.

Dr Allan Reiss, who carried out the study, says it is hoped that they will one day be able to identify the highest-risk groups and intervene early to prevent a lifetime of problems and suffering.

Reiss says as a better understanding of such disorders is gained, treatments can be designed that are more specific and effective.

Approximately one in 100 people will suffer from schizophrenia at some time in their lives and the annual cost to the nation in health care is estimated at more than £2.6bn.

The illness is characterised by changes in thoughts, perception and behaviour, and often strikes people in their 20s or early 30s.

Although one in five sufferers fully recover, an equal number need expensive, long-term treatment.

The remainder partly recover but may suffer relapses.

Although scientists do not know what causes schizophrenia they say there is strong evidence suggesting a biological or genetic basis.

The general population has a 1 per cent chance of developing the illness, and that risk increases to 10 per cent for the close relatives of a patient, and rises for identical twins, to 47 per cent if one is already diagnosed.

The study investigated 24 children who suffered from a genetic mutation known as a deletion on one chromosome.

It is known that about one-third of children with this deletion to part of chromosome 22 will develop schizophrenia.

The deletion occurs in one in 4,000 births.

Dr Reiss says they have strong evidence that this deletion is a major risk factor for the development of schizophrenia or related psychotic conditions.

The study found one of the genes on the part of the chromosome that is missing is responsible for a protein that degrades dopamine, a critical chemical messenger, or "neurotransmitter", in the brain.

Children with the deletion suffer higher-than-normal levels of dopamine, interfering with what scientists call the "Goldilocks effect", when it is important not to have too much or too little, but just enough dopamine.

The scientists followed the children for five years, and as expected, about one-third developed schizophrenia in that time.

Dr Reiss says although this deletion probably causes less than 5 per cent of schizophrenia cases, it is the only well-defined genetic risk factor they have right now.

The study is published in the journal Nature Neuroscience.