Twins and virtual twins: Do genetic (as well as experiential) factors affect developmental risks?

• This is the first comparison of Chinese twins and virtual twins (same-age unrelated siblings).
• This research showed that Age at Adoption added less than other predictors to adoptee’s externalizing and internalizing behaviors.
• Genetic effects were founds for four content areas (Developmental Delays at Adoption, Initial Adaptation to Adoption, Crying/Clinging and Refusal/Avoidance), with shared environmental effects evident for Developmental Delays and Crying/Clinging.

Factors underlying developmental delays and psychosocial risks are of interest to international adoption communities. The current study administered a Pre-Adoption Adversity (PAA) Questionnaire to mostly American parents raising (a) adopted Chinese twins or (b) same-age unrelated adopted siblings. A goal was to replicate earlier analyses of pre-adoption adversity/adjustment among adopted preschool-age Chinese girls. A second goal was to conduct genetic analyses of four content areas (Developmental Delays at Adoption, Initial Adaptation to Adoption, Crying/Clinging, and Refusal/Avoidance) derived from the PAA Questionnaire. A key finding was that age at adoption added less than other predictors to adoptees’ externalizing and internalizing behaviors. Family factors (e.g., parental education) contributed significantly to behavioral outcomes among the adopted Chinese twins. Genetic effects were indicated for all four content areas, with shared environmental effects evident for Developmental Delays at Adoption and Crying/Clinging. Future investigators should consider incorporating genetically sensitive designs into developmental research programs.