Schizophrenia.

Schizophrenia is among the most severe and debilitating of psychiatric disorders. Diagnosis is currently by criterion-based systems, including positive (eg, hallucinations and delusions) and negative (eg, avolition and alogia) symptoms. The importance of negative symptoms in the course and outcome of the illness is increasingly being studied. Current research seeks to detect causal mechanisms in schizophrenia through studies of neural connectivity and function, as well as models of genetic transmission, such as polygenic models of inheritance in genetic research. Potential genes have been identified that may confer vulnerability to the illness, perhaps in conjunction with environmental factors. Neuroimaging research with magnetic resonance imaging and positron emission tomography has investigated differences in volumes and functional dysregulation in specific neural subregions. Areas studied include the frontal and temporal cortex, the hippocampus, the thalamus, and the cerebellum. Despite these advances, treatment of symptoms and psychosocial and cognitive impairments remains only partially successful for many patients.