Maternal smoking during pregnancy does not affect externalizing problem behavior in children

Externalizing problem behaviors are associated with negative long-term outcomes such as antisocial behaviour, substance abuse, and socioeconomic problems. Externalizing behaviour is heritable (~50%) but is also associated with... [ view full abstract ]

Externalizing problem behaviors are associated with negative long-term outcomes such as antisocial behaviour, substance abuse, and socioeconomic problems. Externalizing behaviour is heritable (~50%) but is also associated with environmental risk factors such as maternal smoking during pregnancy (MSDP). A crucial question is: do environmental risk and genetic factors pose an independent effect on externalizing problems, or do they interact?

We tested in two large samples (ABCD; N=1,154 and Generation R, N=2,200) the effects of MSDP and genetic risk on externalizing behavioural problems. MSDP was derived from mother reports, or interviews. Externalizing problems in ABCD were assessed with mother and teacher reports at age 5, and with mother and self reports at age 12 using the Strengths and Difficulties Questionnaire (SDQ). In Generation R, the Child Behavior Checklist was assessed at age 5 and 9 with mother reports. Genetic risk was based on polygenic risk scores (PRS) derived from the largest GWAS to date on antisocial behaviour, (BroadABC N=16,400) and on ADHD (N= 55,374). Our model included PRS of antisocial behaviour or ADHD, MSDP, sex, and educational attainment of the mother.

We observed no main effect of antisocial PRS on externalizing problems in both samples. We did observe a significant positive main effect of MSDP on mother reported externalizing problems, and an interaction effect with antisocial PRS, but only at age 5, and only in ABCD. The ADHD PRS was significantly associated with externalizing problems in both samples, at both ages, but we found no significant effects of MSDP.

Our observations do not strongly support a main or interaction effect of MSDP on externalizing problem behaviors in young children. Future studies should include genetic risk when exploring environmental risk factors for psychopathological problems, such as externalizing problem behaviors.