Cannabis, with its rich spectrum of phytocannabinoids such as THC and CBD, has long been used in traditional medicine relating to fertility and reproduction. Now, scientists are beginning to discover just how important the endocannabinoid system is to the biological mechanisms controlling these fundamental processes.
Does cannabis use affect fertility and the menstrual cycle? The menstrual cycle is complex, and cannabis might influence several aspects and stages. Let’s see what modern research has to say:
1. THC may reduce fertility during ovulation phase
There have been a number of studies conducted on the relationship between the endocannabinoid system and the female reproductive cycle. It has been repeatedly shown that levels of the crucial endocannabinoid anandamide vary drastically at various points of the menstrual cycle.
Anandamide levels appear to be highest at the point of ovulation—the moment that the egg is released from the ovary. As anandamide is an agonist of cannabinoid receptors, one might expect that high levels of THC (which is also an agonist) would not necessarily be detrimental to ovulation.
However, a handful of studies from the 1970s and ‘80s suggest that THC has a strong ability to block ovulation in many mammals, including primates (although there do not appear to be any studies specifically on humans). It appears that THC does so by suppressing the production of a hormone critical to the ovulation process, known as luteinizing hormone.
As with most aspects of cannabinoid science, more research is required to establish exactly what the link between cannabis use and ovulation is. Interestingly, however, it does appear that tolerance to the ovulation-blocking effect of THC may build up in habitual users.
2. Cannabis can reduce painful cramps during menstrual period
Traditionally, cultures all over the world have used cannabis in herbal medicine to treat painful menstrual cramps. Famously, the British Queen Victoria was also said to have used cannabis to soothe her painful cramps. Given that her personal physician was the renowned cannabis doctor William B. O’Shaughnessy, that story is most likely true. The fact that she knighted him some years later, suggests that she must have really appreciated it!
Today, many women continue to use cannabis to soothe their painful cramps, and experience great subjective relief. Despite this, there have been no formal studies to back up its efficacy, and the underlying biological processes at work have not been defined.
However, it is well-known that THC can act as a powerful analgesic and antinociceptive agent. An analgesic is a general term for painkiller; antinociceptives specifically stop the nerves from sensing pain signals at all. As both THC and CBD have the ability to reduce inflammation, this may contribute to the subjective reduction in discomfort.
For those searching for pain relief without the psychoactive effects of THC, CBD can be an adequate solution.
3. Cannabis use may suppress key hormones during premenstrual phase
During the premenstrual phase (which is also known as the luteal phase), hormonal fluctuations can cause a wide range of symptoms. These include pain, irritability, mood swings, fatigue, and bloating. It is well known that levels of certain hormones, including progesterone, significantly increase during this phase (while other hormones, such as oestrogen, become depleted).
When those symptoms are abnormally severe symptoms, this phenomenon is called premenstrual syndrome, or PMS. For years, doctors have prescribed supplementary progesterone as a treatment for severe PMS, but recent research indicates that this is ineffective. The general consensus has been that abnormal premenstrual symptoms are linked to progesterone levels being low at a time when they should be high. In fact, some forms of PMS appear to be linked to excessive progesterone levels and reduced oestrogen levels.
Clearly, premenstrual symptoms severe enough to be classed as PMS are a result of hormonal fluctuations and imbalances. Furthermore, there is evidence to suggest that cannabis use can have several effects during the luteal phase (the window between ovulation itself and commencement of the menstrual period).
Cannabis use can:
- Suppress the level of progesterone
- Alter levels of other important hormones known as prolactin and cortisol
- Inhibit the effect of THC on luteinizing hormone
Again, we have to note that the precise mechanisms at work have not yet been fully researched and verified. But it is clear that the endocannabinoid system has a role to play, and that women who experience abnormal symptoms at this time may benefit from targeted cannabinoid therapies.
Indeed, there are countless women throughout the world who experience subjective relief from cannabis during the premenstrual phase, although this may result from the known anti-anxiety and relaxant effects of cannabis more than from direct influence on hormonal levels.
4. THC may decrease length of menstrual cycle
The evidence for THC causing a shortened menstrual cycle in humans is sparse, but worth mentioning. A 1986 study on the effect of THC on luteinizing hormone observed the overall duration of menstrual cycles decreased in women given cannabis compared to those given a placebo.
Interestingly, older studies on non-human primates indicate that THC may alter cycle length, but not necessarily shorten it. In a 1980 study on rhesus monkeys, the sample treated with THC overwhelmingly exhibited significant increases in cycle duration. One monkey had a cycle length of 145 days, compared to the usual 30!
Obviously, more research is required before it can be said with any degree of certainty how and if the duration of the menstrual cycle is affected in humans. As with the ovulation-blocking effect of THC, it may be that tolerance to any possible effect builds up rapidly.
5. THC may affect embryo implantation in the uterus
There have been several important studies published over the last decade or so, investigating the finely-tuned influence of the endocannabinoid system over various key processes relating to conception and early pregnancy. Several of these studies have found that anandamide levels fluctuate dramatically throughout the monthly cycle. In particular, they show that anandamide levels are at their lowest during the “implantation window”.
Note: The implantation window refers to the brief window of time in which the embryo can successfully implant in the endometrium of the womb. This window typically occurs 6-10 days after ovulation and lasts roughly three days.
In studies where anandamide has been artificially increased at this stage, implantation has generally failed to occur. Given that anandamide and THC are both agonists of the cannabinoid receptors, it seems that consumption of THC during the implantation window could cause the same effect. However, this concept is overly simplistic, and does not necessarily hold up with such a complex system as the EC system.
Further research is needed to verify the association between high-THC cannabis use and the blocking of a fertilised ovum from being implanted in the endometrium during the implantation window. Until then, to be on the safe side, users who want to get pregnant should probably cease use of cannabis at least 24 hours prior to their implantation window opening.
THC for non-hormonal birth control?
THC does appear to have the ability not only to inhibit ovulation but also prevent implantation of fertilised eggs in the endometrium. This suggests that there could be the potential for THC, or compounds like it, to be used as the basis for non-hormonal birth control drugs.
However, as tolerance build-up appears to be something of a problem with THC itself, there are probably better candidates out there for targeted research. After all, if consistent THC use alone were enough to prevent pregnancy, fertility rates would be drastically lower in heavy cannabis users compared to the general population, and there is no indication that this is the case!
Interestingly, there is substantial evidence that cannabis use enhances sexual pleasure in users, which could help to counteract any negative effect on fertility rates!
- Disclaimer:This article is not a substitute for professional medical advice, diagnosis, or treatment. Always consult with your doctor or other licensed medical professional. Do not delay seeking medical advice or disregard medical advice due to something you have read on this website.