Over the years, several studies have demonstrated a detrimental effect of cannabis and marihuana on sperm production, not only in animals but also in human species and therefore on male fertility.  

However, in the past few days media have echoed the news of a possible positive effect of marihuana on semen, starting from a research led by Harvard T.H. Chan School of Public Health, public health school graduate from Harvard University of Boston, Massachusetts (USA) and published on the prestigious international magazine Human Reproduction.  

According to Dr. Miguel Ruiz Jorro, co-director of CREA, assisted reproduction centre in Valencia specialized in Andrology, “this research should be interpreted with due caution, since it shows results observed in a specific group of patients who were consulting for infertility and were submitted to a survey on regular consumption of illegal drugs, such as cocaine and marihuana. After comparing results of semen analyses, patients who have reported smoking or having smoked marijuana, presented a higher sperm count. This could be interpreted like smoking marihuana improves sperm and male fertility and it would undermine what have been stressed out so far by many researches about the deleterious effect of marihuana on sperm. However, these researches have had the same or better scientific repercussion and have also been published on journals of international scale. But they didn’t arouse the same media interest. Saying that smoking marihuana can improve sperm seems to be certainly groundbreaking”.  

As a possible explanation of the paradoxical result observed in the research of this group of Scientifics, the authors  explain that, after data analysis, they observed that patients who have never smoked marihuana, had lower testosterone levels than those who admitted having smoked marihuana, and endogenous higher levels of testosterone are associated with higher sperm count. “This causal relation could be an explanation for the higher number of sperm observed in this group of patients, who also presented an higher consumption of alcohol and tobacco, habits that are clearly related with a worst reproductive potential in male”, as remarked by Dr Ruiz.  

Another limitation of the research is that the consumption of marihuana wasn’t determined by a blood test or another tissue analysis of the patient, but from a survey where patients voluntarily reported if they regularly consume marihuana or if they did it at least once.  “Likewise, it’s important to bear in mind that the survey was led in a country where the use of marihuana is illegal and its consumption can have repercussion on health insurance coverage. Thus there could be patients who didn’t report this habit in the survey”, as explained by Dr. Ruiz.  He also adds: “This doesn’t mean that results are false or lack scientific interest. But it’s important to interpret these results as they are: results obtained from a very specific group and, as the own authors point out, they can’t be extrapolated to general population.”  

Several researches, some of them are very recent, have demonstrated the detrimental effect of cannabis and its byproducts on spermatogenesis and male fertility. Also the genetic information of sperm can be affected, thus consequences will not be limited to the male patient but they would likely affect his descendants. Not to mention the repercussions on a neurological level. The same is true of alcohol and tobacco abuse, that could not only be cause of several serious diseases, but it could also affect fertility and have negative repercussions on the descendant’s health, since sperm DNA integrity is altered.  

On the contrary, many other researches have concluded that a balanced diet and a healthy lifestyle might improve sperm quality and male reproductive potential. 

According to Minerva Ferrer, CREA’s scientific director and contributor to researches performed on the in vitro effect of cannabis on sperm, “To publicize in a generic way that smoking marihuana improves the sperm quality, as it could be wrongly implied from the conclusions of a concrete study, might not only offer a wrong idea, but it could also have a negative effect on the population, especially on those who are involved in a reproductive project. With this we are not only referring to patients with fertility problems but also to possible candidates as sperm donors.”

From CREA, as assisted reproduction centre specialized in Andrology, we recommend that, in case of infertility, the male patient should be clinically evaluated to identify and treat any factor that could affect the pregnancy chances or the health of his descendants. Besides doing a sperm analysis, a detailed clinical history has to be performed and, in some specific cases, a list of complementary tests to determine how to improve the sperm quality and count.   

“Generally speaking, a healthy lifestyle and a balanced diet could improve the chances but the most important thing is indeed to evaluate each case individually”, as concluded by Dr. Ruiz Jorro.