According to a new study, smoking cannabis could have a catastrophic effect on fertility and fetal development. In the United States, cannabis use has nearly doubled in the past decade, with 21.8% of individuals aged 12 years and older – 61.8 million people – reporting marijuana use in 2023. This figure rose from 12.6% reported in 2013.
Researchers from the University of Toronto in Canada suggest that the dramatic rise, partly influenced by the decriminalization and legalization of recreational cannabis, has raised concerns about the drug’s impact on fertility. To understand this claim better, they proceeded by conducting two studies.
The first was a lab study which exposed oocytes, or immature human egg cells, to THC (tetrahydrocannabinol), the psychoactive ingredient that makes one ‘high’ after consuming marijuana. It also measured their chromosomal development.
For the second study, the researchers used data from about 1,059 egg cell fluid samples taken from patients undergoing in-vitro fertilization (IVF), a fertility treatment that involves retrieving eggs from ovaries and manually combining them with sperm in a lab for fertilization.
Meanwhile, it was reported that sixty-two fluid samples tested positive for THC, which resulted in a 6% positivity rate. They were then compared to the ‘clean’ samples to assess how the eggs’ cells developed differently.
At the end of the studies conducted, the researchers found that THC was associated with lower rates of embryos that contained the appropriate number of chromosomes, eventually leading to birth defects and miscarriages. While in the analysis of IVF patients, about 60% of embryos in the THC-positive group had the appropriate number of chromosomes, compared to 67% in the THC-negative group.
Meanwhile, samples used in the study came from females who were below 40 years, and it is unclear when they consumed THC products. Most chromosomally abnormal embryos will either fail to implant in the uterus or will result in a miscarriage, with the abnormality often preventing the embryo from developing further. In rare instances, a chromosomally abnormal embryo may result in a live birth with a genetic disorder, such as Down syndrome.
Additionally, exposing immature egg cells to THC disrupted chromosome stability by increasing errors in spindle formation and causing more eggs with the wrong number of chromosomes. While higher THC levels were linked to faster maturation, this accelerated process was associated with a greater risk of chromosomal abnormalities, leading to a lower proportion of healthy embryos.
The Autism Research Institute also noted concerns about prenatal cannabis exposure increasing autism risk, particularly due to animal studies suggesting THC can lead to genetic mutations.
Chromosomal abnormalities and defects have also been linked as a known risk factor for autism. Meanwhile, these effects were spotted in the recent study with people who had consumed THC products in their systems while they were pregnant or undergoing IVF.
While concluding their investigation, the authors of the recent study finalized that the findings underscore the need for increased awareness and caution among people with ovaries, particularly those undergoing fertility treatments. It also highlighted the importance of informing patients about the potential risks associated with cannabis consumption and provides a basis for regulatory bodies, medical professional societies, and public health organizations to establish recommendations and guidelines regarding cannabis consumption during fertility treatment.
