Changes in genetic and environmental influences on depressive symptoms across adolescence and young adulthood

Background Depression rises markedly in adolescence, a time when increased and new genetic influences have been reported. Aims To examine ‘new’ and ‘stable’ genetic and environmental factors on depressive symptoms in adolescence and young adulthood. Method A questionnaire survey investigated a sample of twin and sibling pairs at three time points over an approximately 3-year period. Over 1800 twin and sibling pairs reported depressive symptoms at the three time points. Data were analysed using multivariate genetic models. Results Depressive symptoms at all time points were moderately heritable with substantial non-shared environmental contributions. Wave I genetic factors accounted for continuity of symptoms at waves 2 and 3. ‘New’ genetic effects at wave 2 also influenced wave 3 symptoms. New non-shared environmental influences emerged at each time point. Conclusions New genetic and environmental influences may explain age-related increases in depression across development.