Positron emission tomography in psychiatry.

Positron emission tomography permits the study of human brain function. With a positron labelled tracer and a model for quantitation, regional brain metabolism and neuroreceptor characteristics can be determined with PET. Schizophrenia is the most extensively studied psychiatric disorder. Most studies have demonstrated decreased metabolic rates in wide areas of the brain. It is proposed that the metabolic changes observed in the brains of schizophrenic patients are due to a fundamental change in neuronal function. Fewer studies have been performed in other psychiatric disorders. Bipolar depressed patients probably have a decreased brain metabolism. Obsessive compulsive and panic disorders (if sensitive to lactate) have an increased brain metabolism. This is probably also the case for female anorectic patients. Alcohol dependent subjects with a long duration of abuse may have a decreased brain metabolism. Neuroreceptor studies with PET have in one study of psychotropic drug naive schizophrenic patients demonstrated an increase of D2-dopamine receptors. In another study no difference between controls and patients was found. Treatment of schizophrenic patients with conventional doses of neuroleptic drugs results in a D2 receptor occupancy of 65 to 85 per cent, suggesting that there is no need for high dose treatment in schizophrenic patients. The studies reviewed clearly demonstrate that PET is a valuable tool in psychiatric research.