For the estimated 2.5 million Americans who suffer from some form of schizophrenia, a newly approved drug and a recent study are important advances in managing and understanding this disease.

Schizophrenia is the most widespread serious mental illness in the United States. It is marked by disturbances of thinking, feeling and behavior and often includes delusions and hallucinations.The approval of the new drug, clozapine, is significant because it is effective in about 25 percent of patients who do not respond to standard antipsychotic drugs, said Dr. Arnold Friedhoff, a psychiatrist at New York University Medical Center.

In addition to calming the agitation and hallucinations associated with schizophrenia, clozapine (marketed as Clozaril) also helps the lack of motivation and emotional and social withdrawal typical of some forms of the illness.

Friedhoff noted that clozapine can't be used to treat every patient with schizophrenia. One of its drawbacks is its potential to produce a potentially fatal blood abnormality in some people. To guard against this, regular blood monitoring is required.

"While the high cost of tests associated with monitoring the drug may restrict its use, clozapine is nonetheless an important new weapon in the arsenal against schizophrenia," Friedhoff said.

Another significant development is a National Institute of Mental Health study of identical twins, one of whom has schizophrenia. The study focused on anatomical differences in the twins' brains.

Magnetic resonance imaging (MRI) graphically demonstrated that the schizophrenic twin's left temporal lobe and hippocampus, areas of the brain involved with memory and emotion, are smaller than those in the healthy twin.

Also, the fluid-filled ventricles (spaces) in the schizophrenic twin's brain are enlarged, suggesting this twin may have less brain tissue.

Friedhoff said many studies have established the presence of genetic factors in schizophrenia. "Since identical twins carry the same genes, each one must have the gene or genes for schizophrenia. But only one twin developed the illness. Therefore, factors other than genetic ones must be involved."

He suggested these nongenetic factors may occur during pregnancy or early in life.

Understanding both genetic and nongenetic factors are essential to future research and treatment, he emphasized.