Biological markers for the schizophrenic and atypical psychoses

This is a review of the present state of knowledge in the area of biological markers that may delineate subpopulations of patients with major psychotic illness. Postmortem studies have revealed that schizophrenia is associated with an excess of dopamine (DA) receptors in the limbic system. A more clinically useful adaptation of this approach has been a study of DA D2 receptors in lymphocytes. Studies of monoamine oxidase, dopamine-beta-hydroxylase, and dimethyltryptamine have not fulfilled their early promise nor have the peptides provided useful information as to possible biological markers. Recent studies of the one-carbon cycle enzymes, methionine adenosyltransferase and serine hydroxymethyltransferase, suggest that underactivity of these, particularly the former, may be a reliable clinical marker for a subgroup of schizophrenics. The computerized axial tomography (CAT) scan abnormalities of schizophrenia establish useful indices of abnormal cerebral anatomy such as cortical atrophy with enlarged ventricles, cortical asymmetries, and atrophy of the cerebellar vermis. Positron emission tomography studies with 18F 2-deoxyglucose (2DG) have shown that many schizophrenics have a higher 2DG uptake in the occipital and temporal rather than the frontal cortex, thus reversing the normal patterns. The dexamethasone suppression test is a valuable biological marker for certain depressions. It may also be useful in identifying subgroups of the schizoaffective disorders, with some schizoaffectives showing an abnormal affective-like response and others not. These and other discriminating biological markers are discussed in this report.