Schizophrenia might be several disorders

PHILADELPHIA, Oct. 23 (UPI) -- Schizophrenia might not be a single disease as traditionally thought but instead a collection of multiple disorders with similar symptoms that affect the brain differently, researchers reported Wednesday.

A study of more than 100 schizophrenics found they can be divided into at least two different groups based on memory impairment and structural and functional differences in their brains, Bruce Turetsky, associate director of neuropsychology at the University of Pennsylvania and principal investigator of the study, told United Press International.

This could have implications for understanding schizophrenia's cause as well as developing treatments for it, Turetsky said. Schizophrenia is a mental disorder that causes hallucinations, delusions, disorganized thinking and other difficulties.

Turetsky's group found 18 percent of the schizophrenics in the study fit into a category called cortical, in which they could not recall a list of words immediately after seeing them or recognize the words upon hearing them later.

About 31 percent of the patients were classified as subcortical. Although they, too, could not recall the word list immediately, they could recognize the words later if the researchers presented the words to them.

The remaining 51 percent suffered only mild memory impairment and did not fit into either group. As Turetsky and colleagues suggest in the October issue of the journal Neuropsychology, these patients could have a mixture of symptoms and brain changes found in the other two groups -- but to a lesser extent.

MRI scans of schizophrenics' brains revealed the cortical and subcortical subtypes had differences in brain structure. The cortical group "had less gray matter, particularly in the temporal lobe," Turetsky said. The brain is composed of white and gray matter. The gray tissue is the command center of the brain and is composed of nerve cells.

"The subcortical group had enlargement of the ventricles," the fluid-filled cavities in the center of the brain, he said. "This reflects some sort of reduction in the surrounding tissue," he said.

Turetsky noted these brain abnormalities had been seen before in schizophrenics but never had been correlated with different subtypes.

Further brain examinations with positron emission tomography or PET scans revealed differences in brain metabolism between these two groups. The cortical schizophrenics had "reduced metabolism in the temporal lobe regions of the brain," an area significantly involved in memory, he said.

The findings should aid research into the causes of schizophrenia because they will ensure researchers are working with groups of patients who share the same problem, Turetsky said. Lumping all schizophrenics together is akin to including patients "with heart disease and patients with lung disease" in a study focused on understanding heart disease, he said.

It has long been recognized there are different subtypes of schizophrenics "but no one has ever shown that there is any implication of those categories in terms of (the cause of the disease) or prognosis," he said. The new findings could give researchers the opportunity to do just that. In addition, a better understanding of the nature of this disease could pave the way for better ways to treat it.

The discovery that metabolic rates for schizophrenics are lower in the temporal lobe region of the brain is highly significant, Paul Thompson, assistant professor of neurology at the neuro-imaging lab at University of California, Los Angeles School of Medicine, told UPI.

"The loss of tissue, together with the extra sign of less activity in the tissue that's still there, helps explain the memory loss in these patients," Thompson said. "In short, you could (scan) to help understand what is wrong, and whether medications are fixing it."

It could be very useful clinically, he explained, "that by scanning a patient, you could see which of these three categories they might belong to. You could say, 'Yes, this person has memory loss and low activity in their temporal lobes, so this medication might work,' or you could say, 'This patient has frontal tissue loss (so they might) respond well to this type of therapy.'"

Robin Frank, spokeswoman for the National Alliance for Research on Schizophrenia and Depression in Great Neck, N.Y., agreed the research may lead to better schizophrenia medications.

"Studies such as Dr. Turetsky's are so important because they shed new light on the underlying mechanisms of the disease," Frank told UPI.

"As scientists gain a better understanding of schizophrenia, the hope is they will be able to develop better treatments for specific groups of patients," she said.

About 2.5 million people in the United States and 1 percent of the world population suffer from schizophrenia.

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(Reported by Steve Mitchell, UPI medical correspondent, in Washington, with additional reporting by Joe Grossman, UPI Science News, in Santa Clara, Calif.)