Does Cannabis Use Increase or Decrease Men’s Sperm Count?

October 4, 2023 ·

Due to the growing acceptance of cannabis, particularly for medical purposes, scientists are increasingly eager to delve into its impact on health. A particular area of interest lies in exploring how marijuana might affect fertility.

Researchers are actively investigating the potential consequences of smoking marijuana on male fertility. Recent studies have revealed concerning trends, indicating that men in Western nations grapple with a fertility crisis. Specifically, the sperm count among males of reproductive age decreased by more than half between 1973 and 2011.

According to data from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, around 9% of men in the United States have encountered issues with infertility. Hence, scientists have been examining how various changeable factors, including lifestyle decisions, could influence male fertility.

In a recent investigation, a group of researchers from the Harvard T. H. Chan School of Public Health in Boston, MA, turned their attention to the impact of marijuana smoking on indicators of male fertility. The results of their study, as outlined in a research paper published in the journal Human Reproduction, contradicted the initial hypothesis they had set forth at the outset of their research.

Study author Jorge Chavarro emphasizes that these surprising results underscore the limited knowledge we possess regarding the impact of marijuana on reproductive health and, more broadly, its overall health effects. He stresses that it’s crucial to exercise caution when interpreting our findings, underscoring the urgency for additional research into the health consequences of marijuana usage.

Increased Sperm Count Among Cannabis Users

While research on the connection between marijuana and fertility is limited, earlier studies have suggested potential adverse effects on semen quality. Additionally, cigarette smoking is well-established as a risk factor for infertility in both males and females.

In light of these known associations, the authors of the recent study initially anticipated that men with a history of marijuana use would demonstrate compromised fertility markers. Dr. Jorge Chavarro, a co-author and associate professor of nutrition and epidemiology at the Harvard T.H. Chan School of Public Health, noted that their expectations were grounded in existing research. Surprisingly, the data they gathered contradicted these expectations.

Chavarro mentioned, “We spent a substantial two months meticulously reviewing all the data to ensure its accuracy. We were genuinely astounded by these findings.”

The research involved an analysis of health surveys and semen samples from over 650 men, primarily of Caucasian ethnicity, predominantly with a college education, and an average age of 36. These men were part of couples seeking fertility treatment at the Massachusetts General Hospital Fertility Center between 2000 and 2017.

Notably, most of the men in the study had average sperm counts, implying that other factors related to conception had brought them and their partners to the hospital, according to Chavarro. To evaluate sperm quality, the researchers collected and scrutinized 1,143 semen samples from the study’s subjects. Additionally, blood samples were drawn from 317 of these men, which were then used to assess reproductive hormone levels.

Furthermore, the researchers administered questionnaires to the participants, inquiring about their marijuana usage habits. This included questions about whether they had ever smoked more than two joints and if they were current marijuana users. The surveys inquired about the participants’ historical and current drug use, alongside other aspects of their lifestyles. Among the men, 55% reported having smoked marijuana at some point, and 11% indicated they were current marijuana users.

The researchers discovered that marijuana users typically had greater sperm concentrations and numbers — two fertility indicators — than individuals who had never used marijuana when comparing the survey responses to the semen sample analysis. Additionally, they exhibited lower levels of a hormone associated with infertility. However, The researchers discovered that men who had previously used marijuana had slightly greater sperm counts than men who did not.

Findings Consistent with Interpretations

Despite the unexpected results, Chavarro asserts that they do not imply that men should use marijuana to improve the quality of their sperm. He clarifies that this does not mean using marijuana will increase sperm count. The goal of the study was not to establish causation but rather to identify associations.

He claims that a much more likely reason is that guys who have greater testosterone levels, who often have more sperm than men who have lower testosterone levels, are also more likely to use marijuana. According to Chavarro, it is well established that high testosterone levels are related to greater engagement in risk-seeking behaviors, including drug use, within normal ranges. Slightly higher sperm counts and semen quality correlate with higher testosterone levels.

Additionally, Chavarro points out that several older research linking drug use to poorer semen quality focused on men with substance misuse problems, who frequently use several substances concurrently, making it challenging to “disentangle what might be marijuana from what might be other drugs.” For instance, the current study also examined cocaine use and discovered a link between it and poorer semen quality, indicating that some substances may harm fertility.

The research shows how little scientists understand about marijuana’s impact on health, according to Chavarro. He explains that they might have expected to find what we initially thought, and that would have made us less surprised, leading to a completely different research paper.

But, the opposite results we discovered made us dig deep into the existing literature on marijuana’s effects on health. Unfortunately, there isn’t much research in this area. So, they mostly rely on assumptions, good intentions, and guesses.

Chavarro mentions that this unexpected discovery has inspired him to investigate marijuana’s effects on reproduction and overall health more thoroughly, especially as legalization and recreational use become more common. In 2017, a survey revealed that over half of American adults have experimented with marijuana, and recent federal data indicates that 5% of pregnant women use cannabis.

Chavarro adds that while legalization is advancing rapidly, our knowledge about the health consequences of marijuana use is not keeping pace. They’re essentially working with very limited data.


The research on the relationship between marijuana use and male fertility has unveiled surprising findings. While initial expectations suggested potential harm to sperm quality, the study revealed higher sperm concentrations among marijuana users.

This unexpected outcome underscores the limited knowledge we have regarding the health effects of marijuana, emphasizing the need for further research as legalization and recreational use become more prevalent. As we navigate this landscape, we must base our understanding on solid scientific data rather than assumptions, reflecting the complex and evolving nature of marijuana’s impact on health and reproduction. (Full Story)

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