Schizophrenia, depression share brain clue.

Schizophrenia, depression share brain clue

Scientists have identified a brain region apparently involved in both schizophrenia and severe depression, two of the most incapacitating psychiatric disorders. The finding, which confirms clinical observations of some overlap between schizophrenia and depression, stems from the largest positron emission tomography (PET) study of psychiatric patients to date, says Richard J. Haier of the University of California, Irvine.

The PET scans show that people with schizophrenia or depression, compared with healthy individuals, have a substantially lower metabolic rate in the brain's frontal lobes and basal ganglia, according to Haier and Irvine colleagues Monte S. Buchsbaum and William E. Bunney. These areas regulate language and other types of complex thought.

The scans reveal differences as well, Haier's group reported last week at a meeting of the International College of Neuropsychopharmacologists, held in Kyoto, Japan. These arise in the limbic system, which regulates emotion. While structures in the limbic system show lowered metabolism among schizophrenics, limbic metabolism runs unusually high among depressed individuals.

"It's hard to say if metabolic rates in specific brain areas relate to specific psychiatric symptoms," Haier points out. "But as we study bigger samples, we hope to identify subcategories of schizophrenia and depression with PET."

The researchers examined 40 severely depressed individuals, 18 schizophrenics and 28 healthy controls. Depressed participants had not used antidepressant drugs for at least several weeks. Schizophrenic volunteers were recruited through Irvine-area psychiatrists and had never taken an antipsychotic medication.

All participants received an injection of harmless, short-lived, radioactive glucose isotopes, which the brain used for energy. A PET scanner recorded gamma rays emitted as the isotopes decayed, revealing areas of high and low brain activity. A computer transformed this information into color-coded images of brain metabolism (SN: 4/30/88, p.280).

Clinicians had previously noted links between depression and schizophrenia. For instance, depression sometimes involves delusions and hallucinations, while schizophrenia can include secondary signs of depression. Moreover, antipsychotic drugs sometimes ease depression, and antidepressants sometimes quell symptoms of schizophrenia.

"These are two separate disorders, but they share disturbed metabolism in a common brain area," Haier concludes.