Family-genetic studies and identification of valid diagnostic categories in adult and child psychiatry.

Family-genetic studies of child and adult psychiatric disorders have become increasingly fashionable over the past decade. The development of structured diagnostic interview schedules, the emergence of uniform diagnostic criteria such as DSM-III, and the use of refined design and analytic techniques from the field of chronic disease epidemiology have made substantial contributions to the methodology of such studies. Advances in molecular genetics, particularly our emerging capacity to perform chromosomal linkage studies throughout the human genome, have renewed hope that the constitutional underpinnings of some psychiatric disorders can be identified and that the pathophysiology of these disorders can be elucidated. Family-genetic techniques in child and adult psychiatry are discussed with a particular focus on their potential value in validating diagnostic categories spanning developmental epochs.