Genetic linkage and schizophrenia: methods, recent findings and future directions.

Family, twin and adoption studies have shown that familial clustering in schizophrenia is predominantly due to genetic factors. On the basis of segregation analyses of the illness distribution in relatives of patients, various models of the mode of transmission have been put forward but as yet there is no consensus. Linkage analysis based on molecular genetic techniques provides a more direct approach to discovering precisely what is inherited (one gene, a small number of genes or many genes?) that generates vulnerability to schizophrenia. To date there has been no sufficiently replicated finding of one or more linked genes and many methodological complexities remain. However, the rate of progress in addressing these issues gives hope that genetic linkage analysis of schizophrenia will provide some answers.