Descriptive statistics are listed in Table 1. Study participants were 35 years old on average (range 19–56 years). Preliminary analyses indicated that demographic variables (participant age, parental age at twins' birth, parental birth year, parental education and parental income) were not significantly associated with childhood maltreatment, so these were not included in subsequent models. Twin pair correlations of key variables are shown in Table 2. Childhood maltreatment and AAD were positively correlated both within and across members of twin pairs. MZ pair correlations were greater than DZ pair correlations, consistent with genetic influences on childhood maltreatment and AAD. However, the cross-twin cross-trait (childhood maltreatment–AAD) correlations were not significantly different for MZ compared with DZ pairs, suggesting that the childhood maltreatment–AAD association was not explained by genetic influences.
