Therapeutic signposts: using biomarkers to guide better treatment of schizophrenia and other psychotic disorders.

We propose that various measures of brain structure or function, gene expression and proteomic technologies can be used to guide better treatment of schizophrenia and other psychotic disorders. These measures are not used to establish a specific diagnosis. Their purpose is to predict variations in underlying illness activity that predict severity, course of clinical illness, or other morbidity. We propose a new instrument that uses a composite scoring system of systemic biomarkers of illness-related changes in health status: the Brain and Mind Research Institute Biomarker Index. This may permit comparison of biological dysfunction among patients who are at similar points in their illness or have similar clinical features. A specific example of the use of a novel positron emission tomography marker of progressive brain disease in patients with schizophrenia is described.