Prenatal Cannabis Plus Tobacco Exposure Was Linked to Worse Behavior Problems in Children
Children exposed to both cannabis and tobacco during pregnancy showed greater externalizing behavior problems at ages 9-11 than those exposed to either substance alone, with higher tobacco doses amplifying the negative effect of cannabis.
Quick Facts
What This Study Found
Prenatal co-exposure to cannabis and tobacco was associated with significantly greater externalizing behavior problems (aggression, rule-breaking) compared to either substance alone. Higher daily quantities of tobacco amplified the negative behavioral effects of cannabis exposure on both externalizing and internalizing scores (p<0.01). No significant interaction was found for internalizing behaviors in the main analysis.
Key Numbers
n=9,792 total (290 co-exposed, 225 cannabis-only, 966 tobacco-only, 8,311 unexposed); cannabis main effect p=0.03; tobacco main effect p<value; cannabis x tobacco interaction for externalizing p=0.032; dose-response interaction p<0.01 for both externalizing and internalizing.
How They Did This
Cross-sectional analysis of baseline data from the ABCD Study (children ages 9-11), comparing Childhood Behavior Checklist scores across four groups: cannabis+tobacco co-exposed (n=290), cannabis-only (n=225), tobacco-only (n=966), and unexposed controls (n=8,311), using 2x2 ANCOVA with covariate adjustment.
Why This Research Matters
Cannabis and tobacco are commonly co-used during pregnancy, but most research examines each substance in isolation. This study provides evidence that their combined prenatal effects on child behavior may be worse than either alone, which is particularly relevant as cannabis use during pregnancy rises.
The Bigger Picture
This study is part of the ABCD Study, the largest long-term study of brain development in the US. The finding that co-exposure is more harmful than individual exposure supports the idea that prenatal substance interactions can compound developmental risk.
What This Study Doesn't Tell Us
Cross-sectional baseline data cannot establish causation or developmental trajectory. Prenatal exposure is based on maternal self-report, which may underestimate true exposure. Cannot fully control for other prenatal and postnatal environmental factors that differ between exposure groups.
Questions This Raises
- ?Do these behavioral differences persist or change as children enter adolescence?
- ?What biological mechanisms explain the interactive effect of cannabis and tobacco?
- ?Would the findings differ with more precise exposure measurement (timing, dose, frequency)?
Trust & Context
- Key Stat:
- Cannabis + tobacco co-exposure during pregnancy was linked to worse child behavior than either substance alone
- Evidence Grade:
- Moderate: Large sample from the well-designed ABCD Study, but cross-sectional analysis with self-reported exposure limits causal inference.
- Study Age:
- Published in 2025 using ABCD Study baseline data (children ages 9-11).
- Original Title:
- Prenatal Cannabis and Tobacco Co-Exposure and Its Association with Behavioural Outcomes in Middle Childhood: Co-exposition prénatale au cannabis et au tabac et son association avec les résultats comportementaux au cours de l'enfance intermédiaire.
- Published In:
- Canadian journal of psychiatry. Revue canadienne de psychiatrie, 70(1), 41-53 (2025)
- Authors:
- Nadler, Emma(2), Jacobus, Joanna(14), Rabin, Rachel A(10)
- Database ID:
- RTHC-07224
Evidence Hierarchy
A snapshot of a population at one point in time.
What do these levels mean? →Frequently Asked Questions
What are externalizing behaviors?
Externalizing behaviors include outward-directed problems like aggression, rule-breaking, and conduct issues. In this study, they were measured using the Childhood Behavior Checklist, a widely validated assessment tool for children.
Why does tobacco amplify the effect of cannabis?
The biological mechanism is not fully understood, but both substances affect fetal brain development through different pathways. Tobacco may increase cannabis absorption or compound its effects on developing neural circuits involved in behavioral regulation.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-07224APA
Nadler, Emma; Jacobus, Joanna; Rabin, Rachel A. (2025). Prenatal Cannabis and Tobacco Co-Exposure and Its Association with Behavioural Outcomes in Middle Childhood: Co-exposition prénatale au cannabis et au tabac et son association avec les résultats comportementaux au cours de l'enfance intermédiaire.. Canadian journal of psychiatry. Revue canadienne de psychiatrie, 70(1), 41-53. https://doi.org/10.1177/07067437241271696
MLA
Nadler, Emma, et al. "Prenatal Cannabis and Tobacco Co-Exposure and Its Association with Behavioural Outcomes in Middle Childhood: Co-exposition prénatale au cannabis et au tabac et son association avec les résultats comportementaux au cours de l'enfance intermédiaire.." Canadian journal of psychiatry. Revue canadienne de psychiatrie, 2025. https://doi.org/10.1177/07067437241271696
RethinkTHC
RethinkTHC Research Database. "Prenatal Cannabis and Tobacco Co-Exposure and Its Associatio..." RTHC-07224. Retrieved from https://rethinkthc.com/research/nadler-2025-prenatal-cannabis-and-tobacco
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.