Molecular genetics of psychopathologies: a search for simple answers to complex problems.

Molecular genetics is helping define the contribution of genetic involvement in behavioral disorders. At this time, however, a severely limiting factor for DNA linkage studies of these disorders remains the definition of the phenotype. An example of this is found in the group of studies examining linkage of schizophrenia to the 5q location. Although various broad clinical interpretations of the schizophrenia phenotype were used to test for linkage, all but one study reported findings negative for linkage of schizophrenia to the 5q area. We offer a strategy based on family studies using segregation data of behavioral subtypes. We apply this strategy using molecular genetic technology to our study of psychopathology in patients. This approach offers the possibility of a clearer definition of the phenotype and is suggested for use in both linkage and association studies of neuropsychiatric disorders.