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Does smoking cannabis affect sperm count and fertility?

Does smoking cannabis affect sperm count and fertility?

With the recent legalisation of marijuana across several countries and the permitted medical use in the UK, further research is being carried out on how this psychoactive compound affects our bodies. The use of cannabis both in recreational and medicinal settings has since started to be more accepted, considering 147 million people consume it annually and that cannabis is the most cultivated and trafficked drug worldwide.

Marijuana is composed of more than 400 compounds, 60 of which are cannabinoids. The active compounds in this plant are varied, but one of the most studied ones are tetrahydrocannabinol (THC) and cannabidiol (CBD). Our body is packed of endogenous endocannabinoids and its receptors, known as the endocannabinoid system, which regulates homeostatic processes, such as sleeping and relaxing. Our internal endocannabinoid system has pivotal roles in our nervous system, contributing to its development and plasticity.

Cannabis targets the endocannabinoid system, binding to cannabinoid receptors CB1 and CB2. THC acts mainly on CB1 receptors, although it retains certain affinity to CB2 receptors too. CB1 receptors are extensively found in our brain cells, as well as in fat cells, liver cells, musculoskeletal tissue, gonads, and connective tissue. CB2 receptors are mainly associated with immune cells and to an extent they are expressed in our nervous system.

With the current loosening regulations on cannabis, researchers have more freedom to explore different aspects of this compound and how its consumption affects our bodies. A group of scientists from Duke University recently published their findings on the effects of THC on sperm. Their objective was to assess whether THC does alter the sperm’s epigenome and if so, to explore in which ways it induces changes.

They explored these questions on both animals and human participants. The main observations were that indeed THC does alter sperm’s epigenetic landscape, triggering changes near genes associated with two main cellular pathways. These are the Hippo signaling pathway, which controls our organs growth to their adequate size, and Pathways in Cancer associated with programmed cell death. Additionally, some of the altered genes were associated with the Ascorbate and Aldarate metabolism, which is part of carbohydrate metabolism processes.

The alterations in genes associated with such pathways was clarified from studying the 24 participants’ sperm epigenome. They found that the user group tended to show lower levels of methyl tags on their epigenome compared to the non-user group, and it tended to negatively correlate with levels of THC in their urine. Meaning, the more THC concentrations within their bodies, the less methylated their sperm appeared in the genes associated with such pathways, compared to non-users.

Interestingly, they also observed that cannabis users seemed to have reduced sperm concentrations when compared to non-users that partook in the experiment. What they could not corroborate was whether these alterations were passed on to the zygote. Longer studies following up the participants may be necessary to assess the capacity of the altered sperm due to THC to fertilize the egg. The Duke team plans on tackling such remaining questions and further investigating the effects of THC on sperm.

On the flip side, it is always important to consider that scientific research is not necessarily absolute and has its limitations. This study is preliminary and would need further testing in order to establish the robustness of the findings. Considering the fairly small number of participants and potential confounders that were not accounted for, future larger replicates of the study will help provide conclusive answers to the extent on which THC does indeed cause such alterations and for how long. Other factors that need standardising and accounting for include the dose-dependent effects, consumption route, and THC composition of the marijuana strain used.

Nonetheless, the Duke team proved that it is essential to further explore the effects of cannabis since the prevalence of use it is worldwide. The researchers suggest that when thinking about starting a family it may be beneficial to be cautious and assume that the changes will remain in one’s sperm for a period, thus reducing or stopping cannabis consumption 6 months to a year prior preconception.

- Claudia Ghezzou

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