This study is the first to assess marijuana's effects on specific swimming behavior of sperm from marijuana smokers and to compare the results with sperm from men with confirmed fertility. Marijuana contains the cannabinoid drug THC (tetrahydrocannabinol), which is its primary psychoactive chemical, as well as other cannabinoids.
Results of the study were presented today (Oct. 13, 2003) at the annual meeting of the American Society of Reproductive Medicine in San Antonio.
"The bottom line is, the active ingredients in marijuana are doing something to sperm, and the numbers are in the direction toward infertility," said Lani J. Burkman, Ph.D., lead author on the study. Burkman is assistant professor of gynecology/obstetrics and urology and head of the Section on Andrology in the UB School of Medicine and Biomedical Sciences. UB's andrology laboratory also carries out sophisticated diagnosis for infertile couples.
"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 improper timing of sperm function by direct stimulation, or it may be bypassing natural inhibition mechanisms. Whatever the cause, the sperm are swimming too fast too early." This aberrant pattern has been connected to infertility in other studies, she noted.
Burkman collaborated on earlier, published UB research that was the first to show that human sperm contains cannabinoid receptors, and that the naturally occurring cannabinoid, anandamide, which activates cannabinoid receptors in the brain and other organs, also activates receptors in sperm. This evidence indicated an important role in reproduction for natural cannabinoids.
Further research 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. When researchers tested synthetic anandamide equivalents on human sperm, the normal vigorous swimming patterns were changed and the sperm showed reduced ability to attach to the egg before fertilization. Only about 10 laboratories in the U.S. perform this array of sperm function tests.
In the current study, Burkman received seminal fluid from 22 confirmed marijuana smokers and subjected the samples to a variety of tests. The volunteers 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.
The samples from both groups were tested for volume, sperm-count-per-unit of seminal fluid, total sperm count, percent of sperm that was moving, velocity and sperm shape. Sperm also were assessed for an important function called hyperactivation (HA), a closely regulated and very vigorous type of swimming that is required as the sperm approaches the egg. The researchers evaluated HA and velocity while the sperm was in seminal fluid and again after washing and incubation, when the dead sperm were eliminated.
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 when HA and velocity, both before and after washing, were assessed, the study found.
"The sperm from marijuana smokers were moving too fast too early," said Burkman. "The timing was all wrong. These sperm will experience burnout before they reach the egg and would not be capable of fertilization."
Burkman noted 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.
As to the question of whether fertility potential returns when smokers stop using marijuana: Burkman said the issue hasn't been studied well enough to provide a definitive answer.
"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."
Additional scientists on the study included Herbert Schuel, Ph.D., UB professor of pathology and anatomical sciences, and the staff of the andrology laboratory.