Family, twin, and adoption studies have suggested an important role for
hereditary factors in the etiology and pathogenesis of several psychiatric
disorders. Advances in molecular and statistical genetics may very well
reveal the identity of these factors, which may include single genes.
Linked markers, critical to the discovery of abnormal genes in several
medical conditions, have been reported for Huntington's disease,
Alzheimer's disease, bipolar disorder, and schizophrenia. Psychiatric
disorders pose particular problems (etiologic heterogeneity, incomplete
penetrance, variable expressivity) for genetic research. New practical and
ethical questions also arise. Nevertheless, knowledge may emerge that will
suggest new approaches to diagnosis, prevention, and treatment.