Rat offspring exposed to smoked cannabis during gestation showed different and generally milder behavioral changes than those exposed to injected THC or CBD, suggesting the method of exposure matters significantly.
Prenatal researchers, obstetricians, anyone interested in cannabis and pregnancy
Injected THC had more severe effects on offspring than smoked cannabis across multiple behavioral measures
What the researchers found
Injected THC and CBD had more severe impacts on maternal and litter health and produced distinct behavioral patterns compared to smoked cannabis. High-THC smoke decreased prepulse inhibition (a measure of sensory filtering) in adolescent female offspring, which normalized by adulthood. Injected THC increased exploratory behavior in both sexes.
Why it matters
Most preclinical research on prenatal cannabis exposure uses injected THC at high doses, but most pregnant humans who use cannabis smoke it. This study shows the route of exposure produces meaningfully different offspring outcomes, suggesting prior injection-based research may not reflect real-world risk.
The numbers in context
High-THC smoke decreased PPI and MK-801-induced locomotor activity in adolescent females (normalized by adulthood); injected THC increased exploratory behavior in both sexes; injected CBD impaired PPI in both sexes in adulthood; all gestational exposures impaired odor-based recognition tasks regardless of treatment type
How the study worked
Pregnant rats were exposed to high-THC or high-CBD cannabis smoke or received THC or CBD injections during gestation. Offspring were tested on prepulse inhibition, locomotor activity, social interaction, object recognition, and attention tasks during adolescence and adulthood.
What this study cannot tell us
Rat model may not translate to humans, specific cannabis strains and doses used, cannot isolate combustion byproducts from cannabinoid effects in smoke group, limited behavioral battery
How to read the evidence
Single animal study comparing exposure routes; novel design but limited to one strain of rats and specific cannabis varieties
When this study was published
Published 2025
The bigger picture
The cannabis and pregnancy research field has largely relied on injected THC studies. This head-to-head comparison suggests those studies may overestimate some risks while missing others specific to smoked exposure, calling for more research using realistic exposure methods.
Questions still open
- Do the milder effects of smoked cannabis reflect lower cannabinoid delivery or different pharmacokinetics? Would vaporized cannabis produce yet another pattern? Do the adolescent effects that normalized by adulthood truly resolve or simply become subtler?
Common questions
Does it matter whether prenatal cannabis exposure is smoked or injected in research?
Did prenatal cannabis exposure cause lasting behavioral problems in offspring?
Read the original research
Differential effects of gestational Cannabis smoke and phytocannabinoid injections on male and female rat offspring behavior.
Progress in neuro-psychopharmacology & biological psychiatry, 136, 111241
Citation
Black, Tallan; Barnard, Ilne L; Baccetto, Sarah L; Greba, Quentin; Orvold, Spencer N; Austin-Scott, Faith V L; Sanfuego, Genre B; Onofrychuk, Timothy J; Glass, Aiden E; Andres, Rachel M; Macfarlane, Leah M; Adrian, Jesse C; Heidt, Ashton L; McElroy, Dan L; Laprairie, Robert B; Howland, John G. (2025). Differential effects of gestational Cannabis smoke and phytocannabinoid injections on male and female rat offspring behavior.. Progress in neuro-psychopharmacology & biological psychiatry, 136, 111241. https://doi.org/10.1016/j.pnpbp.2024.111241
Explore the wider topic
- How to Talk to Your Teenager About Weed (Without Losing Them)
- My Kid's Friends Smoke Weed: A Parent's Guide
- I Smoke Weed But Don't Want My Kids To: Navigating the Hypocrisy
- Quitting Weed as a Parent: Why It Is the Hardest and Most Important Quit
- Quitting Weed as a Teen or Young Adult
- My Kid Is Smoking Weed: A Parent's Guide