The Link between depression in mothers and offspring: an extended twin analysis.

Family studies have shown that maternal depression is a risk factor for depression in children. It is unclear, however, to what extent the familial transmission of depression from mother to child involves genes and how much is due to environmental adversity. This study used an extended twin design to assess the importance of environmental factors in the association of depression in mothers and children while simultaneously accounting for genetic relatedness in a UK. community sample of twins aged 8 to 17 years and their mothers. A model that constrained the genetic and environmental parameters to be equal within the two generations and included genetic and environmental paths between mother and offspring (twins) was tested with data from 1468 families. Significant environmental paths were found when maternal ratings were used. When cross-informant data were used (maternal depression and child self-reports of depression), the environmental path was no longer significant. However, for cross-informant data where children were classified as having high depression scores or scores within the normal range, significant environmental effects were found. These findings are interpreted in light of the strengths and weaknesses of the extended twin and other designs.