Impact of Marijuana on Sperm Reveals Mixed Effects

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Impact of Marijuana on Sperm Reveals Mixed Effects

Evaluation of the impact of marijuana use on semen quality: a prospective analysis


Marijuana also known as cannabis, weed or pot, and its active metabolite delta-9-tetrahydrocannabinol (THC) can interfere with the signalling system of sperm by competing with internal cannabinoids at cannabinoid-binding receptors (CB1, CB2) leading to a negative effect on spermatogenesis, sperm function and male fertility.

In vitro studies with THC show a clear negative dose-dependent effect on sperm motility and inhibition of acrosome reactions, while mouse studies observed changes to Sertoli cell signalling, decreased sperm motility and impaired fecundity.

Earlier human studies reaffirmed the negative effects of THC on male reproductive health and semen quality however a recent single-center study in the US reported higher sperm concentrations and total sperm counts among marijuana users compared to non-users.

Researchers have suggested the effect of marijuana on male fertility may be non-linear, with low to moderate use possibly pro-spermatogenic and higher doses anti-spermatogenic, however new studies are required to confirm this hypothesis.


To characterise the differences in semen quality between men who reported consumption of marijuana and men who did not in a large cohort.


A total of 409 men presenting for infertility evaluation at the University of Washington Men’s Health Center each completed a reproductive health questionnaire and provided a semen sample.

Males diagnosed with azoospermia, genetic mutations, genital infection or other known causes of infertility (i.e. varicocele, testicular atrophy, gonadotoxins) were automatically excluded to minimise potential bias.

Consumption of marijuana was classified as never, current or past-users, meaning at least 3 months of abstinence prior to semen analysis. Quantification of marijuana use was not ascertained in this study due to the challenges in standardizing the different forms of consumption.

Analysis of semen samples was carried out according to the World Health Organization (WHO) 2010, 5th Edition guidelines with the 95th percentile reference values used to define normal and abnormal results.


Among the 409 men, 173 reported current or past use of marijuana. Final group sizes was;

  • Never, n=235
  • Past-user, n=103
  • Current, n=71

Mean duration of marijuana use was 9.4 years, among past or current-users, with a mean age of 35 compared to 36.3 years in never-users.

The majority of participants had BMI ⩾ 25, although never-users were less likely (71.1%) compared to both current (74.7%) or past-users (77.7%). Unsurprisingly tobacco use was also more prevalent among current-users (36.6%), however tobacco use was unreported in 40 never-users ruling out any conclusions.

Analysis of semen parameters identified no significant differences between the 3 groups with the exception of strict morphology, which was significantly worse among marijuana users.

However further analysis according to results, below (abnormal) or above (normal), the WHO reference values showed that current users were more likely to have abnormal semen volume and strict morphology. On the other hand, never-users were more likely to have abnormal sperm motility levels, compared to current and past-users.

After adjusting for age, BMI, and tobacco use, advanced statistical (multivariate logistic regression) analysis of the data showed that current marijuana users had significantly

  • increased odds of abnormal strict morphology (adjusted Odds Ratio = 2.15)
  • increased odds of abnormal semen volume (adjusted Odds Ratio = 2.76)
  • reduced odds of abnormal total motility (adjusted Odds ratio = 0.47)

There was also a trend among current-users towards abnormal total progressive motile count (adjusted Odds Ratio = 1.71), due to the reduction in semen volume. 

Interestingly the risk of abnormal strict morphology was highest for past-users (adjusted Odds Ratio = 2.26) indicating a delayed effect of marijuana use on sperm morphology.

However, the two-fold increase in likelihood of sperm motility above the WHO minimum reference value confirms the mild pro-spermatogenic effect reported previously.

Based on these results the authors concluded confidently that men with reduced total progressive motile sperm count or teratozoospermia cease use of marijuana while trying to conceive.


Marijuana exhibited mixed effects on male fertility, doubling the risk of abnormal sperm morphology and semen volume (adj. Odds Ratio: 2.2 and 2.8), which increases the likelihood of abnormal total progressive motile sperm count, however the risk of abnormal total motility was surprisingly halved.


  1. Lack of quantification of marijuana consumption
  2. Male fertility not entirely dependent on WHO semen parameters
  3. Only males seeking fertility treatment were recruited limiting the generalisation of any findings


No external funding was declared for this study.


Acrosome reaction
A reaction that occurs in the acrosome of the sperm after sperm capacitation.

The breakdown and or reabsorption of tissues.

A complete absence of sperm in ejaculated semen.

The capacity to produce offspring.

Any substance or drug that can cause temporary or permanent damage to the ovaries or testicles.

In vitro
An experiment performed outside the living organism usually within a laboratory.

Chemical structures, composed of protein, that receive and transduce signals within a biological system.

Sertoli cells
Somatic cells essential for testis formation and spermatogenesis.

The process by which a complex, interdependent population of germ cells produces spermatozoa (sperm).

Less than 4% morphologically normal sperms.

An enlargement of the veins within the scrotum.

Similar studies

Nassan F L, et al. (2019). Marijuana smoking and markers of testicular function among men from a fertility centre.

Gundersen T D, et al. (2015). Association between use of marijuana and male reproductive hormones and semen quality: a study among 1,215 healthy young men.

Pacey A A, et al. (2014). Modifiable and non-modifiable risk factors for poor sperm morphology.


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