Bipolar Disorder and Schizophrenia
Have Similar Genetic Roots

(September 12, 2001) -- 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.

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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.

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