Co-use of tobacco and marijuana during pregnancy: Pathways to externalizing behavior problems in early childhood.

Use and co-use of tobacco and marijuana during pregnancy are associated with the development of social, cognitive, and behavioral problems for infants and children. However, less is known about the potential developmental impact of the use of tobacco and marijuana in tandem. The present study examined an etiological model for the development of externalizing behavior problems (EBP) in early childhood in a high risk sample (N = 247) of mother-infant dyads with prospective data from pregnancy to 36 months of child age. Co-use during pregnancy and continued maternal tobacco and marijuana use from infancy through early childhood were investigated. Although direct pathways from exposure during pregnancy to EBP were not significant, there was a significant indirect pathway from prenatal tobacco use to EBP via lower breastfeeding duration to lower maternal warmth/sensitivity to EBP, and a pathway from higher maternal affective dysregulation to higher EBP. These results highlight the importance of considering cascading effects of substance use during pregnancy on parental processes within the context of developmental risk and protection.