The role of psychological probes in genetic studies of schizophrenia.

The success of the neurosciences in opening pathways to the understanding of psychotic disorders has led to enormous optimism about solutions to the mysteries of these illnesses. Yet the Holy Grail for this field--the discovery linkage between a chromosomal locus that is linked to a diseased gene--has thus far eluded us, whereas it has been grasped in such disorders as cystic fibrosis, Huntington's disease, and neurofibromatosis. This paper argues that those biological studies that bypass the psychological domain, and have directly attempted to find biochemical measures associated with schizophrenia, probably will not succeed. Seeking direct links from such molar behaviors as psychotic symptoms to molecular events has not worked in the past, and is not likely to work in the future. The approach recommended here focuses on working one's way from the behavioral through the psychological and psychophysiological levels toward the neural, biochemical and molecular levels. Psychology has much strength to contribute in the search for traits that broaden the phenotype of schizophrenia. Examples are given in the study of eye movement abnormalities as aids in the genetic exploration of schizophrenia.