Clinical perspectives on the genetics of schizophrenia: a bottom-up orientation.

Phenomenology has been the reference point that investigators have used in their efforts to understand schizophrenia. Although symptoms and signs are crucial for the diagnosis of schizophrenia, there is an ongoing debate since Kraepelin attempted to group symptoms to understand the etiology of schizophrenia. Several operational criteria have been developed to establish the diagnosis of schizophrenia, making it obvious that there are no precise symptomatological boundaries. There is little clear indication which of the systems is valid for genetic and other biological research. Despite the enormous effort to find a linkage between schizophrenia and one or more loci, the results are far from conclusive. Another approach is the search for candidate genes of whichDISCI and 22q11 deletion syndrome are examples.