GENETIC AND ENVIRONMENTAL-INFLUENCES ON DEPRESSIVE SYMPTOMATOLOGY IN ADOLESCENCE - INDIVIDUAL-DIFFERENCES AND EXTREME SCORES

The purpose of the current investigation was to compare the genetic an d environmental influences on individual differences in depressive sym ptomatology (as assessed using the Children's Depression inventory) to such influences on extreme scores in an unselected sample of adolesce nts. The sample included 707 pairs of siblings (average ages 14.5 and 12.9 years, respectively) participating in a combined twin- and step-f amily study. Moderate genetic influence was found for the full range o f individual differences in depression; in contrast, there was nonsign ificant genetic influence, and significant shared environmental influe nce, on extreme scores. The results were interpreted using a risk mode l in which familial influences specific to the high end of the distrib ution contribute to depressive symptomatology in adolescence.