Psychosis endophenotypes in schizophrenia and bipolar disorder.

Recent studies provide considerable evidence that schizophrenia and bipolar disorder may share overlapping etiologic determinants. Identifying disease-related genetic effects is a major focus in schizophrenia and bipolar disorder research, with implications for clarifying diagnosis and developing specific treatments for various impairments in these 2 disorders. Efforts have been multifaceted, with the ultimate goal of describing causal paths from specific genetic variants, to changes in neuronal functioning, and to behavioral and functional impairments. Parallel efforts have identified and refined several alternative phenotypes that are stable, heritable, some with known biological substrates, and are associated with psychosis liability. These alternative phenotypes are likely to aid search for liability genes in schizophrenia and bipolar disorders and likely to be informative regarding the extent to which the 2 disorders share etio-pathophysiology.