Linking different mental illnesses through genetics
(HealthDay News) The way the brain works or doesn't is a mystery that isn't easily solved.
Even as medical research continues to advance and reveal new ways to treat the physical ravages of cancer and coronary disease, finding ways to combat mental illness remain elusive.
Recent research from Cambridge University in England has given the latest clue that may indeed begin to unravel the intricacies of the human mind.
The baseline revolves around genetic composition. Schizophrenia and bipolar disorder (once known as manic depression), which have traditionally been regarded as unrelated mental disorders, appear to have the same underlying genetic defect.
A study of preserved brains of people who had schizophrenia and bipolar disorder finds flawed performance of the genes that produce the protective coating around brain cells, says a study by scientists at the University of Cambridge .
The protective coat consists of fatty molecules called myelin, held together by proteins. The study of gene activity in the preserved brains shows that "those proteins appear to be abnormal," says study author Dr. Sabine Bahn, who directs a neurological research group Cambridge . The study appeared in the Lancet.
The finding adds evidence for a growing belief that "these conditions are not as different as has been commonly thought," she says. "The diagnosis is often imprecise, and it can take months or years to arrive at the correct diagnosis."
Together, the two conditions affect about 2 percent of the population. Manic depression is a milder condition than schizophrenia, which has severe effects on social behavior and memory.
It's possible that this research could someday lead to better treatment for the illnesses, but that is a long-range hope, Bahn says. A more immediate goal is a quicker and more accurate diagnostic test to help psychiatrists prescribe the best treatment.
Even that goal does not seem easy to achieve, she acknowledges. The finding is based on the study of just 45 brains at the Stanley Library of Brain Research in Bethesda , Md. -- 15 of deceased patients diagnosed with schizophrenia, 15 of patients with bipolar disorder, and 15 of people free from mental disease.
It's possible to monitor the activity of specific genes in preserved brains by measuring the amounts of the specific RNA molecules produced by each gene. The study showed abnormal activity of genes in oligodendrocytes, the cells that produce the myelin sheath.
In thinking of a diagnostic test, "we are hoping that something that is abnormal in the brain may be abnormal in peripheral tissue," Bahn says. "Or perhaps we could look at brain images to get the information."
Her group's studies are being expanded, to look first at samples from another 150 preserved brains and eventually at more than 20,000 postmortem tissue samples, Bahn says. The idea is to determine exactly what is going wrong in the psychotic brain.
"One possibility is that the myelin change is a marker of something much more fundamental," she says. "We could be just scratching the surface."
The study is an important marker of "a sea change in what we in the field think is the likely culprit in psychosis," says Dr. Kenneth L. Davis, author of an accompanying editorial in the Lancet .
He did some of the earliest work on myelin abnormalities as head of the department of psychiatry at the Mount Sinai School of Medicine in New York City and now is Chief Executive Officer of the Mount Sinai Medical Center .
Until recently, research on mental disorders focused almost entirely on how signals are transmitted between the synapses at the ends of nerve cells, Davis says. "Now we are focusing on the oligodendrocyte and the maintenance of the myelin sheath, how the message is transmitted through the cabling rather than through the synapse," he says.
The change in focus means that possible links can be seen between mental illnesses and physical diseases such as multiple sclerosis, which involve myelin abnormalities, Davis says.
Over the longer run, he says, "we should be developing a whole series of drugs that affect these different processes, rather than just activity at the synapse," he says.
On the Web
You can learn about bipolar disorder from the National Institute of Mental Health and schizophrenia from the National Library of Medicine.
Sabine Bahn, M.D., Ph.D., group leader, molecular neuropsychiatry research group, Institute of Biotechnology, University of Cambridge, England; Kenneth L. Davis, M.D., Professor And Chief Executive Officer, The Mount Sinai Medical Center, and Psychiatry Professor, Pharmacology and Biological Chemistry, Mount Sinai School of Medicine, New York City; Sept. 6, 2003, The Lancet
Publication date: December 2007
Ed Edelson, HealthDay Reporter
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