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For years, scientists have debated how cannabis impacts male reproductive health. With increasing cannabis use around the world, questions about its long-term effects on hormones and fertility have gained urgency. Some research suggests that cannabis might negatively affect sperm quality and lower testosterone levels, while other studies find little evidence supporting these claims. Due to these conflicting results, researchers have been searching for clearer insights.
A recent study from the University of Geneva (UNIGE) in Switzerland offers a surprising new perspective. The research indicates that, in young men, cannabis use does not decrease testosterone levels—in fact, it might even boost testosterone production in the testes. The findings were published in the journal Communications Medicine.
The study was conducted by scientists from the University of Geneva in partnership with the Swiss Center for Applied Human Toxicology. Their objective was to better understand how cannabis influences the body’s hormonal systems, especially those involved in male reproduction.
Male fertility is affected by many factors, including hormone levels, sperm production, lifestyle choices, age, and overall health. Testosterone, one of the key male sex hormones, plays a central role in sexual development, muscle growth, bone density, and reproductive function. Because of its importance, researchers have long wondered whether cannabis use can alter testosterone levels.
Previous research has yielded mixed results. Some studies found that cannabis users had lower sperm counts, reduced motility, and poorer overall sperm quality. Others saw little to no direct effect of cannabis on reproductive hormones. One challenge in these studies was that many focused only on individual hormones, providing an incomplete picture.
In this new investigation, the researchers took a broader approach. They analyzed blood samples from 94 Swiss military recruits aged 18 to 23, split evenly between 47 confirmed cannabis users and 47 non-users. Rather than targeting a single hormone, they measured hundreds of steroid hormones and related compounds circulating in the blood. This comprehensive analysis allowed for a deeper understanding of how cannabis might influence the endocrine system, which regulates many vital body functions.
Results showed that cannabis users had testosterone levels approximately 23% higher than those of non-users. Further examination revealed that this increase stemmed specifically from the testes. Hormones produced by the adrenal glands, which also produce androgens, did not show similar changes. The findings suggest that cannabis may directly impact Leydig cells—the specialized cells inside the testes responsible for testosterone production.
The study also identified two hormone-related substances, hydroxyprogesterone and dihydroprogesterone, which are derived from progesterone—a hormone involved in reproductive health. These compounds were significantly elevated in cannabis users and may serve as new biological markers of regular cannabis use. Tracking these markers could help researchers better understand how cannabis influences the hormonal system and monitor hormone-related changes over time.
However, higher testosterone levels do not automatically translate into increased fertility. The relationship between testosterone and reproductive health is complex. Fertility depends on sperm count, motility, morphology, hormone balance, and various other biological factors. An increase in testosterone alone does not guarantee improved fertility.
The researchers proposed several possible reasons for the observed testosterone increase. One theory is that the body might be compensating for reduced sensitivity of certain hormone receptors caused by cannabis exposure. Another possibility is that young men with naturally higher testosterone levels may be more inclined to engage in risk-taking behaviors, including cannabis use.
As an observational study, it cannot establish causality—only an association between cannabis use and higher testosterone levels. The most significant strength of this research lies in its comprehensive analysis of numerous hormones rather than just a single measurement, offering a more complete view of cannabis’s potential effects on the endocrine system.
Nonetheless, the study has limitations. Its sample size was relatively small, all participants were young Swiss men, and the findings may not apply to older individuals or those from different populations.
Overall, these results challenge the common belief that cannabis automatically reduces testosterone levels. They also emphasize how much remains unknown about the relationship between cannabis and male fertility. Further long-term research is necessary to determine if certain levels of cannabis exposure could become harmful or if the hormonal changes observed have significant impacts on reproductive health.
This study was published in Communications Medicine.
Source: University of Geneva.
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