Preconception and prenatal cannabis use and the risk of behavioural and emotional problems in the offspring; a multi-informant prospective longitudinal study.

Background: Studies of the long-term consequences of maternal cannabis use on child development beyond the neonatal period are sparse. In the current study, we use a multi-information approach to assess the association of prenatal cannabis exposure and child behavioural and emotional functioning. To explore the possible causal nature of the association, we investigated whether maternal tobacco and paternal cannabis use during pregnancy were also associated with child problems.

Methods: The study population included children of a population-based birth cohort in The Netherlands (n = 5903). Information on parental cannabis use was collected using questionnaires; urine of mothers was analysed for the presence of cannabis metabolites. Child behavioural and emotional problems at approximately 7-10 years were measured using validated teacher-, child- and mother-reports.

Results: Our findings show associations of maternal cannabis use during pregnancy with offspring externalising problems (B = 0.53; 95% CI: 0.29-0.77), but not with internalising problems (B = -0.10; 95% CI: -0.31-0.11). However, maternal cannabis use before pregnancy was also associated with offspring externalising problems (B = 0.27; 95% CI: 0.02-0.52). Further, cannabis use by the father was associated with child externalising problems (B = 0.36; 95% CI: 0.22-0.49) but not internalising problems.

Conclusions: Prenatal exposure to maternal cannabis use is specifically associated with offspring behavioural problems, but not emotional problems. This association is probably not due to an effect of intrauterine cannabis exposure on fetal development, because both maternal and paternal cannabis exposure during pregnancy were related to offspring externalising problems. Our findings suggest that the association can be explained through residual confounding, most likely through shared genetic vulnerabilities for parental cannabis use and offspring behavioural problems.