A mouse study found that 30 days of daily THC (10 mg/kg) did not affect testicular weight, sperm motility, sperm concentration, or in vitro fertilization outcomes, and did not cause DNA methylation changes in brain or embryos, contradicting the belief that THC harms male reproductive processes.
Reproductive medicine researchers; men concerned about cannabis effects on fertility; scientists studying epigenetic effects of drug exposure.
No difference in sperm motility, concentration, or IVF success between THC-treated and control mice
What the researchers found
Researchers gave male mice daily THC (10 mg/kg) for 30 days and compared reproductive outcomes to vehicle-treated controls.
THC treatment decreased cannabinoid receptor 1 (Cnr1) gene expression in the brain cortex but not in the testes.
Testicular and epididymal weight showed no differences between groups. Histological analysis of the testes was normal in THC-treated mice.
Sperm motility and concentration were unaffected by chronic THC.
DNA methylation analysis at three CpG regions of the Cnr1 gene showed no changes in either brain tissue or embryos generated by in vitro fertilization.
IVF outcomes were no different when using sperm from THC-treated versus control mice.
The authors stated their findings contradict the belief that THC consumption has a negative effect on male reproductive processes.
Why it matters
Previous studies have linked chronic cannabis use to sperm abnormalities and decreased fertility. This controlled mouse study found no such effects, suggesting the relationship between THC and male fertility may be more nuanced than previously assumed.
The numbers in context
10 mg/kg/day THC for 30 days. No significant differences in: testicular weight, epididymal weight, testicular histology, sperm motility, sperm concentration, DNA methylation at 3 CpG regions, or IVF embryo production. Cnr1 mRNA decreased in cortex but not testes.
How the study worked
Mouse study with 30-day chronic THC treatment (10 mg/kg/day) versus vehicle. Assessed testicular weight, histology, sperm motility, sperm concentration, Cnr1 gene expression, DNA methylation (bisulfite sequencing), and IVF outcomes.
What this study cannot tell us
Mouse model may not translate to human reproductive physiology. Single dose level (10 mg/kg) may not capture dose-response effects. 30-day exposure may be insufficient to detect long-term damage. IVF is an artificial system that may not reflect natural conception. Only three CpG regions assessed for methylation.
How to read the evidence
Preliminary. Single mouse study with one dose level. Contradicts some prior findings, so replication is needed.
When this study was published
Published in 2018. Research on cannabis and male fertility has continued with mixed findings across studies.
The bigger picture
The effect of cannabis on male fertility is a common concern, especially as use increases among men of reproductive age. This study adds a data point suggesting that at least in mice, chronic THC at moderate doses does not impair basic reproductive function or embryo viability.
Questions still open
- Would higher THC doses or longer exposure reveal reproductive effects? Do human sperm respond differently to chronic THC than mouse sperm? Could THC affect reproductive outcomes through mechanisms not measured in this study (e.g., sperm DNA fragmentation)?
Common questions
Does this mean cannabis is safe for male fertility?
What is DNA methylation and why does it matter?
Read the original research
Effect of chronic THC administration in the reproductive organs of male mice, spermatozoa and in vitro fertilization.
Biochemical pharmacology, 157, 294-303
Citation
López-Cardona, A P; Ibarra-Lecue, I; Laguna-Barraza, R; Pérez-Cerezales, S; Urigüen, L; Agirregoitia, N; Gutiérrez-Adán, A; Agirregoitia, E. (2018). Effect of chronic THC administration in the reproductive organs of male mice, spermatozoa and in vitro fertilization.. Biochemical pharmacology, 157, 294-303. https://doi.org/10.1016/j.bcp.2018.07.045
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