Developments in Brief : Evidence Grows That a Small Number of Genes May Produce Mental Illnesses

A new-found gene that may cause a third of all manic-depressive disorders provides strong evidence that several genes may produce the illnesses, scientists say. That is the second genetic link between heredity and mental illness to be reported in less than four weeks.

“We may end up with a fairly small number,” said Dr. Miron Baron, one of the discoverers of the latest gene.

Last month, scientists studying an Amish family in Pennsylvania reported that they had linked a different gene to cases of manic-depressive disorder. That announcement was hailed as the first solid evidence of a gene’s involvement in a psychiatric disorder.

Baron said it may take years to isolate and study the latest gene. Understanding the gene should help reveal what goes wrong biochemically to produce the disease, and perhaps lead to therapies, he said.

Dr. David Housman of the Massachusetts Institute of Technology, co-author of the Amish report, said he would not be surprised if five genes responsible for the disease eventually are identified.

The latest finding, published in the current issue of the British journal Nature, “is another piece of a puzzle that we have to assemble in order to get the whole picture of bipolar illness and the other major mental disorders,” said Dr. Darrell Regier of the National Institutes of Health.

Manic-depressive illness occurs in up to 2 million Americans. It is characterized by extreme mood swings and impaired judgment.