Male rats exposed to THC for 28 days before mating with drug-naive females produced offspring with significant locomotor hyperactivity during adolescence and impaired learning and memory.
Reproductive health researchers, prospective parents who use cannabis, and epigenetics researchers.
Paternal THC caused offspring hyperactivity and learning deficits
What the researchers found
Offspring of THC-exposed fathers showed adolescent hyperactivity (at 2 mg/kg dose), faster decline in novel object interest (at 2 mg/kg), and delayed radial-arm maze learning (at 4 mg/kg). These effects persisted despite the mothers never being exposed to THC.
Why it matters
Most cannabis-pregnancy research focuses on maternal exposure. This study shows that paternal THC exposure before conception can also affect offspring development, likely through epigenetic changes in sperm previously documented by the same research group.
The numbers in context
THC doses: 2 or 4 mg/kg/day for 28 days. 2 mg/kg offspring: adolescent hyperactivity and faster novel object interest decline. 4 mg/kg offspring: delayed radial-arm maze learning.
How the study worked
Male rats received 0, 2, or 4 mg/kg/day THC subcutaneously for 28 days, then mated with drug-naive females. Offspring were tested for locomotor activity, novel object recognition, and radial-arm maze learning.
What this study cannot tell us
Animal study with subcutaneous THC injection, not typical human exposure. The specific epigenetic mechanisms linking paternal exposure to offspring behavior were not characterized in this study. Sample sizes for behavioral testing were not specified.
How to read the evidence
Preliminary: animal study demonstrating a cross-generational effect, building on prior epigenetic findings.
When this study was published
Published in 2020 in Neurotoxicology.
The bigger picture
The finding that a father's cannabis use before conception can affect offspring behavior represents an important expansion of how we think about cannabis risks, beyond the traditional focus on maternal exposure during pregnancy.
Questions still open
- Do human fathers' cannabis use before conception affect their children's development? Are the epigenetic changes in sperm reversible after THC cessation? Would longer pre-conception abstinence periods prevent these effects?
Common questions
How can a father's drug use affect offspring?
Does this apply to humans?
Read the original research
Paternal factors in neurodevelopmental toxicology: THC exposure of male rats causes long-lasting neurobehavioral effects in their offspring.
Neurotoxicology, 78, 57-63
Citation
Holloway, Zade R; Hawkey, Andrew B; Pippin, Erica; White, Hannah; Wells, Corinne; Kenou, Bruny; Rezvani, Amir H; Murphy, Susan K; Levin, Edward D. (2020). Paternal factors in neurodevelopmental toxicology: THC exposure of male rats causes long-lasting neurobehavioral effects in their offspring.. Neurotoxicology, 78, 57-63. https://doi.org/10.1016/j.neuro.2020.01.009
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