THC exposure during pregnancy impaired adult offspring cognition via CB1 receptors, while maternal immune activation operated through CB2 receptors, and surprisingly, combining both exposures cancelled out the cognitive deficits.
Prenatal researchers, neuroscientists, cannabinoid pharmacologists
Combined prenatal THC and maternal infection paradoxically cancelled cognitive deficits seen with either exposure alone
What the researchers found
PCE impaired novel object recognition and working memory in males via CB1 receptors; MIA impaired the same tasks via CB2 receptors; combined PCE+MIA did not produce cognitive deficits; CB2 knockout prevented the protective effect of combined exposure.
Why it matters
Many pregnant women face both infection and cannabis exposure, and understanding how these interact at the receptor level is important for assessing combined risk.
The numbers in context
THC 3 mg/kg daily from GD5 to PND10; Poly I:C at GD16.5; male offspring showed impaired novel object recognition and working memory from either PCE or MIA alone; females showed more modest changes; combined exposure negated deficits in wildtype males.
How the study worked
Compared wildtype, CB1 knockout, and CB2 knockout mice across four conditions: control, perinatal cannabis exposure (3 mg/kg THC daily GD5-PND10), maternal immune activation (Poly I:C at GD16.5), and combined; tested adult offspring on emotional and cognitive behaviors.
What this study cannot tell us
Mouse model; single THC dose level; MIA model using Poly I:C may not fully represent human infections; the protective effect of combined exposure may not translate to humans; behavioral tests capture limited cognitive domains.
How to read the evidence
Well-designed knockout study with multiple comparison groups and sex-stratified analysis, but single THC dose and mouse model limit clinical translation.
When this study was published
Published 2025
The bigger picture
The finding that two harmful exposures can paradoxically cancel each other out reveals unexpected complexity in how prenatal insults interact, with implications for risk assessment in real-world scenarios.
Questions still open
- What mechanism allows combined PCE and MIA to cancel cognitive deficits? Does this paradoxical protection occur in humans? Would different THC doses or infection timing change the interaction?
Common questions
Did prenatal THC affect offspring brain function?
What happened when both THC and infection were present?
Read the original research
CB1 and CB2 receptors differentially modulate the cognitive impact of maternal immune activation and perinatal cannabinoid exposure.
Behavioural brain research, 485, 115543
Citation
Chen, Han-Ting; Mackie, Ken. (2025). CB1 and CB2 receptors differentially modulate the cognitive impact of maternal immune activation and perinatal cannabinoid exposure.. Behavioural brain research, 485, 115543. https://doi.org/10.1016/j.bbr.2025.115543
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