Prevalence of affective disorder in the child and adolescent offspring of a single kindred: a pilot study.

The study determined the prevalence of psychiatric disorders among the child and adolescent offspring of an extended family identified through a proband with bipolar affective disorder. All of the not mentally retarded offspring (ages 6 to 17 years) of a single extended bipolar affective disorder pedigree were studied. Data regarding psychiatric diagnoses, intelligence, school achievement, temperament, and family functioning were collected using structured and standardized instruments. When the child and adolescent offspring were stratified by degree of genetic relationship to an adult with an affective disorder, there were no differences in demographic variables, IQ, school achievement, or most temperamental and family characteristics. In contrast, there were increases in the rates of affective disorders and disruptive behavior disorders in the offspring that correlated with the degree of genetic relationship to an affected adult. The risk of developing an early onset affective disorder is correlated with the degree of genetic relatedness to affected adults in this single, extended family. This pilot study demonstrates that the inclusion of extended relatives in high-risk studies can enhance the discrimination of genetic and environmental contributions to the development of affective disorders.