The availability of twin data also allows us to test whether there is evidence consistent with a causal interpretation of the childhood maltreatment–AAD association using bivariate structural twin models. Structural equation modeling partitions the sources of variation in a variable (or covariation between two variables) into: additive genetic (A) variance shared by twins due to genetic alleles that combine additively; common environmental (C) variance shared by twins reared together (as are all twin pairs in this sample); and non-shared environmental (E) unique to individuals.
