Marijuana contains the cannabinoid drug THC (tetrahydrocannabinol), its primary psychoactive chemical, as well as other cannabinoids. Several studies have linked marijuana usage and male infertility but how the use of the drug affects infertility has been attributed to a variety of reasons. One study found that men who smoke marijuana frequently have significantly less seminal fluid, a lower total sperm count and their sperm behave abnormally. All of these factors could adversely affect fertility. The University at Buffalo study was the first to exam marijuana’s effects on the specific swimming behavior of sperm from marijuana smokers and to compare the results with sperm from men with confirmed fertility. While researchers are still unsure of the exact reasons for these effects, the results of studies clearly reveal that the active ingredients found in marijuana impact sperm and negatively impact fertility, according to Lani J. Burkman, PhD, lead author on the study. “We don’t know exactly what is happening to change sperm functioning,” said Burkman, “but we think it is one of two things: THC may be causing the improper timing of sperm function by direct stimulation, or it may be bypassing natural inhibition mechanisms.”

Changes in Sperm Enzyme Cap

Researchers have linked this aberrant pattern to infertility in other studies as well. The Buffalo study also discovered in the andrology laboratory showed that human sperm exposed to high levels of THC displayed abnormal changes in the sperm enzyme cap, called the acrosome.

Testing for Sperm Count

Burkman and colleagues received seminal fluid from 22 confirmed marijuana smokers and subjected the samples to a variety of tests. The volunteer subjects reported smoking marijuana approximately 14 times a week, and for an average of 5.1 years. Control numbers were obtained from 59 fertile men who had produced a pregnancy. All men abstained from sexual activity for two days before the lab analysis. From both groups, samples were tested for volume, sperm-count-per-unit of seminal fluid, total sperm count, percent of sperm that was moving, velocity and sperm shape.

Marijuana Smokers Had Less Sperm

Results showed that both the volume of seminal fluid and the total number of sperm from marijuana smokers were significantly less than for fertile control men. Significant differences also appeared with hyaluronic acid (an anionic, nonsulfated glycosaminoglycan distributed widely throughout connective, epithelial, and neural tissues) and velocity, both before and after washing, were assessed, the study found.

Marijuana Use May Be Risky for Borderline Fertility Men

The researchers acknowledged that many men who smoke marijuana have fathered children. “The men who are most affected likely have naturally occurring borderline fertility potential, and THC from marijuana may push them over the edge into infertility,” she said. “THC remains stored in fat for a long period, so the process may be quite slow. We can’t say that everything will go back to normal. Most men who have borderline fertility are unaware of that fact. It’s difficult to know who is at risk. I definitely would advise anyone trying to conceive not to smoke marijuana, and that would include women as well as men.”

Crossing the Fertilization Signals

Later research by Burkman and associates found that marijuana use can inhibit the chemical signaling processes that take place during fertilization. Marijuana use can interfere with arachidonoylethanolamide (AEA) present in human seminal plasma, mid-cycle oviductal fluid, and follicular fluid. Sperm is exposed to these reproductive fluids as they move from the vagina to the site of fertilization in the oviduct. The researchers found that AEA-signaling may regulate sperm functions required for fertilization in human reproductive tracts, and that smoking of marijuana could impact these processes.

Disrupting Sperm Functions

Other studies have found that marijuana use can disrupt the endocannabinoid system (ECS), which is involved in the regulation of male reproduction. A variety of in vivo and in vitro studies found that marijuana disrupts the hypothalamus-pituitary-gonadal axis, spermatogenesis, and various sperm functions. Another study of the endocannabinoid system found that marijuana can inhibit the signaling function of FAAH (fatty acid amide hydrolase) which they found has a central role in an array of reproductive signals, which plays a role in controlling several steps of sperm biology.