Context: A number of studies report an association between maternal smoking during pregnancy (MSDP) and offspring conduct disorder. However, past research evidences difficulty disaggregating prenatal environmental from genetic and postnatal environmental influences.
Objective: To examine the relationship between MSDP and offspring conduct problems in geneticallyrelated and genetically-unrelated mother-child pairs. Design, Setting, and Participants: Three studies employing distinct but complementary research designs were utilized: The Christchurch Health and Development Study (CHDS) (a longitudinal cohort study that includes biological and adopted children), the Early Growth and Development Study (EGDS) (a longitudinal adoption at birth study), and the Cardiff IVF study (genetically-related and -unrelated families; adoption at conception). MSDP was measured as a number of average cigarettes/day (0, 1–9 or 10+) during pregnancy. A number of possible covariates (child gender, ethnicity, maternal age at birth, maternal education, family SES, family breakdown, birth weight and breast feeding (CHDS), placement age (EGDS), and parenting practices) were controlled in the model. Main Outcome Measure: Child conduct problems (age 4–10 years) reported by parents and/or teachers using the Rutter and Conners behaviour scales (CHDS), the Child Behavior Checklist and Children’s Behavior Questionnaire (EGDS), and the Strengths and Difficulties Questionnaire (Cardiff IVF study). Results: A significant dose response relationship between MSDP and child conduct problems was observed in both the genetically-related and genetically-unrelated (adoption at birth) mother-child pairs across three individual studies. The results of the meta-analysis confirmed these findings in the pooled samples. The association, however, was not observed in genetically-unrelated mother-child pairs (adoption at conception).
Conclusions: The findings across the three studies using a complement of research designs suggest that a dose-specific association between MSDP and child conduct problems is observed when passive gene postnatal environment correlation is removed, but not when passive gene–prenatal environment correlation is removed.