High-risk research in schizophrenia: a summary of what has been learned.

High-risk research on schizophrenia has been concerned chiefly with two types of issues: (1) description of background factors in the early lives of high-risk subjects; and (2) identification of biological variables that may be markers of the genetic liability to schizophrenic disorders. It is concluded that efforts to describe background factors have led to some conflicting results, have shown little evidence of specificity of the factors under study to risk for schizophrenia, and may not be generalizable to most individuals who develop schizophrenia. Results of research focusing on biological variables are summarized under the headings of attention and information processing (AIP), smooth pursuit eye movement (SPEM), neurological signs, electrodermal responding, event related potentials, and ventricular size. Of these, certain AIP and SPEM dysfunctions show substantial evidence of serving as biological markers, certain other AIP impairments are promising in this regard, electrodermal responsivity is not, and the other three categories present uncertain or conflicting results. Several methodological issues that have hampered the first generation of high-risk research are discussed.