Male mice given CBD daily for 34 days showed a 76% decrease in testosterone, 38% fewer sperm, and abnormal sperm morphology, with changes persisting after a 35-day recovery period.
Read this if you use CBD regularly and are concerned about potential effects on male fertility.
76% testosterone decrease and 38% fewer sperm after chronic CBD in mice
What the researchers found
Researchers gave young male mice daily oral CBD at two doses (15 and 30 mg/kg) for 34 consecutive days, then allowed a 35-day recovery period before assessing reproductive parameters.
The higher CBD dose caused a 76% decrease in total circulating testosterone, though levels remained within the physiological normal range. Both doses significantly altered the stages of sperm development (spermatogenesis), increasing early stages while decreasing later stages. The number of Sertoli cells, which support sperm development, was reduced at the higher dose.
In both CBD groups, sperm counts in the epididymis were reduced by 38%, and the remaining sperm showed head abnormalities and cytoplasmic droplets on the flagellum, indicating impaired sperm maturation.
These changes were observed after the 35-day recovery period, meaning they persisted well after CBD exposure stopped. This raises questions about the reversibility of CBD's reproductive effects.
Why it matters
CBD is increasingly used chronically, including by young people and children with epilepsy. The finding that chronic exposure reduces testosterone, impairs sperm production, and causes morphological abnormalities raises important safety questions that have not been adequately addressed in human studies. The persistence of effects after a recovery period is particularly concerning.
The numbers in context
CBD doses: 15 and 30 mg/kg daily for 34 days. 35-day recovery period before assessment. 76% decrease in testosterone at higher dose (remained within normal range: 240-1100 ng/dL). 38% reduction in epididymal sperm count in both CBD groups. Increased stages I-VI of spermatogenesis, decreased stages VII-VIII and XII. Decreased Sertoli cells at higher dose. Sperm head abnormalities and flagellum cytoplasmic droplets in both groups.
How the study worked
Male Swiss mice at 21 days of age received oral CBD at 15 or 30 mg/kg daily for 34 consecutive days, with a control group receiving sunflower oil. After a 35-day recovery period, reproductive organs were weighed, testosterone measured, and spermatogenesis, sperm production, and sperm morphology were assessed through histomorphometry.
What this study cannot tell us
This is a mouse study, and doses relative to body weight are much higher than typical human CBD use. The reproductive physiology of mice differs from humans in important ways. Only two doses were tested, and lower doses closer to human clinical use were not examined. The study assessed a single time point after recovery and could not determine if longer recovery would reverse the effects.
How to read the evidence
This is a controlled animal study providing preliminary evidence of CBD reproductive toxicity that needs human validation.
When this study was published
Published in 2018. Human reproductive safety data for chronic CBD use remains limited.
The bigger picture
As CBD products become mainstream wellness products used daily by millions, reproductive safety data become critical. This animal study adds to limited evidence suggesting cannabinoids may affect male reproductive function. The growing use of CBD in pediatric epilepsy makes these findings particularly relevant, as long-term treatment during development could have reproductive consequences.
Questions still open
- Do these findings translate to human males using CBD chronically? Are the effects reversible with longer recovery periods? Should male fertility be monitored in patients on long-term CBD treatment? Do the doses used reflect clinically relevant human exposure levels?
Common questions
Can CBD affect male fertility?
Did the effects go away after stopping CBD?
Read the original research
Chronic exposure to cannabidiol induces reproductive toxicity in male Swiss mice.
Journal of applied toxicology : JAT, 38(9), 1215-1223
Citation
Carvalho, Renata K; Santos, Monaliza L; Souza, Maingredy R; Rocha, Thiago L; Guimarães, Francisco S; Anselmo-Franci, Janete A; Mazaro-Costa, Renata. (2018). Chronic exposure to cannabidiol induces reproductive toxicity in male Swiss mice.. Journal of applied toxicology : JAT, 38(9), 1215-1223. https://doi.org/10.1002/jat.3631
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