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Friday, 11 January, 2002, 00:52 GMT
Mental illness 'in the genes'
The genetic discovery could help scientists work out what is abnormal in the brains of the mentally ill
Research on the brain is difficult to conduct
Researchers have found compelling evidence that mental illness may lie in the genes.

A study indicates that people with a rare version of Prader Willi syndrome (PWS) are susceptible to mental illness.

The condition is caused by the loss of a small part of chromosome 15 inherited from the father, or - in the rarer form - by inheriting two copies of the mother's chromosome 15.

The study suggests a particular gene on that same chromosome may be linked to the occurrence of psychotic illness.

It is unlikely that one gene will be found to underlie all psychotic illness

Marjorie Wallace, Sane
The findings could pave the way for more research into the genetic causes of mental illness in the general population.

PWS is a developmental disorder which results in reduced muscle tone at birth, impaired sexual development, extreme overeating, short stature and mild learning disabilities.

It affects an estimated one in 29,000 births, but the specific genes which lead to it are unknown.

Research problem

In the study, researchers looked at 25 adults with PWS.

Seven (28%), all aged over 28, had a severe mental illness, such as a mood disorder.

All five patients in the study who had the form of PWS where two copes of chromosome 15 come from the mother had a mental illness.

Of the other two who had a mental illness, one had the more common form of PWS, and the other a very rare genetic variant.

Dr Anthony Holland, a consultant psychiatrist at the University of Cambridge, who led the research, told BBC News Online the discovery could inform future research into the genetic causes of mental illness.

He said the problem with research into any major psychotic illness was that it related to abnormalities in the brain.

"You can't easily research the brain like you can with other organs in the body.


"We know there's a genetic vulnerability to conditions such as manic depressive disorder.

"If we can identify what genes predispose to these conditions, we might be able to identify what is abnormal in the brain for those people with severe mental illness."

Marjorie Wallace, chief executive of Sane, the mental health charity, said: "It is unlikely that one gene will be found to underlie all psychotic illness.

"It is known that psychotic illness has a genetic basis (there is a 50% chance that if an identical twin has psychosis, the other twin will be equally affected).

"But all research in this area is essential if we are to find better treatments and eventual cure for these devastating mental illnesses."

The research is published in The Lancet.

See also:

22 Aug 01 | Health
Panic attack gene breakthrough
06 Apr 01 | Health
'Suicidal genes' identified
14 Jun 00 | Health
'Gene for panic attacks'
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