In a study of 247 mother-infant dyads, boys exposed to both tobacco and cannabis prenatally showed blunted emotional reactivity as toddlers, while continued postnatal cannabis exposure was associated with heightened reactivity.
Developmental psychologists, prenatal substance use counselors, and early childhood intervention specialists
247 dyads tracked from first trimester through toddlerhood
What the researchers found
Prenatal tobacco-cannabis co-exposure had a direct effect on blunted toddler reactivity in males only. Mothers who used substances had the highest anger/hostility and mood unpredictability. Continued postnatal cannabis exposure was associated with higher toddler reactivity. Prenatal anger/hostility and mood unpredictability predicted higher infant reactivity, which in turn predicted higher toddler reactivity.
Why it matters
The sex-specific blunting effect of prenatal co-exposure, combined with the heightening effect of continued postnatal cannabis exposure, suggests complex developmental pathways that differ for boys and girls.
The numbers in context
247 dyads at recruitment, 190 at toddler assessment; direct effect of co-exposure on blunted male toddler reactivity; highest anger/hostility and mood unpredictability in substance-using mothers; postnatal cannabis exposure associated with higher toddler reactivity
How the study worked
Prospective longitudinal study of 247 dyads recruited during the first trimester into tobacco-using (including cannabis co-users) and non-substance-using groups. Maternal mood, substance use, and infant/toddler reactivity were assessed across multiple time points using structural equation modeling.
What this study cannot tell us
Cannot fully separate tobacco and cannabis effects in co-users; maternal mood confounds substance exposure effects; relatively small subgroups; observational design with potential unmeasured confounders; attrition from 247 to 190
How to read the evidence
Prospective longitudinal design with prenatal recruitment and multiple assessments, though limited by inability to isolate individual substance effects.
When this study was published
2024 study
The bigger picture
Emotional reactivity in toddlerhood has implications for later behavioral regulation and mental health. Understanding how prenatal substance exposure shapes these early responses can inform early intervention.
Questions still open
- Why does prenatal co-exposure blunt reactivity in boys specifically? Does the blunted reactivity persist into childhood? Could targeting postnatal cannabis use reduce toddler emotional dysregulation?
Common questions
How did prenatal substance exposure affect toddler emotions?
Did maternal mood play a role?
Read the original research
Prenatal tobacco and tobacco-Cannabis co-exposure and unpredictability in maternal anger/hostility: Implications for toddler reactivity.
Neurotoxicology and teratology, 106, 107399
Citation
Kelm, Madison R; Schuetze, Pamela; Eiden, Rina D. (2024). Prenatal tobacco and tobacco-Cannabis co-exposure and unpredictability in maternal anger/hostility: Implications for toddler reactivity.. Neurotoxicology and teratology, 106, 107399. https://doi.org/10.1016/j.ntt.2024.107399
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