Divergent Mental Disorders Linked

Schizophrenia and bipolar disorder, two diseases on opposite sides
of the spectrum of psychosis, may share genetic roots. Researchers
recently found reduced expression of genes responsible for developing the
myelin sheath--a fatty coating that insulates nerve cells--in the
preserved brains of both people who had schizophrenia and in those who
had bipolar disorder.

The two psychological disorders are markedly different.
Schizophrenics tend to withdraw from reality. Bipolar disorder, by
contrast, is marked by wild swings between euphoria and depression. But
lead author Sabine Bahn, at the University of Cambridge, believes that
the two brain disorders both damage the myelin sheath. When that
insulation layer is lost, nerve cells cannot conduct signals
properly.

The finding may suggest a new way to prevent both diseases from
damaging the brain, Bahn suggests. "When a twin has schizophrenia," she
says, "its pair has only a 50 percent chance of developing the disease.
That means something can happen to prevent it from developing." She
cautiously envisions that a blood test could determine who is genetically
predisposed to develop either disease, and medical treatment might help
protect the brain.

The question of why one person would develop schizophrenia and
another suffer from bipolar disorder remains a mystery. "People who
develop schizophrenia may not cope as well with the changes in the brain
as those who develop bipolar disorder," Bahn says.

In the United States, more than 4 million people suffer from the
two disorders, currently treated with different classes of anti-psychotic
drugs. In particular, schizophrenia is an "enormous burden on patients
and society," Bahn says. "It is one of the top five most disabling
diseases."

Because myelin degeneration also underlies multiple sclerosis, Bahn
hopes to apply similar techniques to the brains of MS patients. "We need
to look more globally," she says of employing sensitive techniques to
compare genetic material. "We can't look at it as a fishing expedition.
It may be that apparently unrelated diseases are in fact related."

The study recently appeared in
The Lancet.