One of the most visited articles on this site is this one, what's the relationship between cannabis and testosterone. And since it was a bit old, it's time to expand the topic. So here it is the information about weed and testosterone: bigger, badder and bolder.
Now, popular wisdom tells us that cannabis and testosterone don't mesh well. In fact, it's quite possible that you have heard somewhere that cannabis lowers your testosterone levels.
As always here we are going to take a look at scientific proof, because, especially in these delicate topics, it's easy to confuse opinion with facts.
- 1 The origin of the story about cannabis lowering testosterone
- 2 The need of looking further into testosterone and cannabis
- 3 The crucial difference between casual use and heavy use of cannabis and testosterone
- 4 The relationship between cortisol and cannabis
- 5 The case for medical marijuana and testosterone
- 6 The bottom line about testosterone and cannabis
- 7 Studies referenced
The origin of the story about cannabis lowering testosterone
Where and when did originate the story of cannabis whacking your testosterone?
Well, one of the earliest studies was made in 1974 (1). In such study, Kolodny and his colleagues reported lowered levels of Plasma testosterone in chronic marijuana users, and the numbers were not something to take lightly.
The cannabis heavy users had 416 ± 34 ng per 100 ml, meanwhile, the control-group mean had 742 ± 29 ng per 100 ml — for age-matched men who had never used marihuana.
That's a lot, in fact, it's your testosterone cut in half. So since those numbers were made public, cannabis and testosterone were considered a big no-no.
The need of looking further into testosterone and cannabis
If you have read the testosterone book (or the testosterone companion for that matter) you will know that one study is not enough to reach conclusions. We should see if there is contrary evidence or if other studies replicated the same result.
And it turns out that it was not so clear.
That same year, Mendelson and his colleagues tried to replicate the same effects that Kolodny(2) but they were not the same, in fact, it seemed that cannabis had no relationship with lowered testosterone.
Just one year after that, another study (3) tried to see who was right, Kolodny or Mendelson. And it seemed that Mendelson was right.
I quote: "Data collected in our laboratory support the latter finding".
The latter finding being that testosterone was not significantly lowered by cannabis or lowered at all.
In that experiment, twelve men, ranging from 21 to 38 years of age, and varying from occasional to heavy users of marijuana, were housed for five days on a drug-research ward.
And testosterone levels were normal after cannabis usage. Our beloved hormone was not lowered.
Although the myth persists, because "cannabis lowering testosterone" is a much better headline that "everything is fine and you can continue smoking your weed", there are a lot of studies about this. And generally, they could not recreate the same testosterone lowering results that Kolodny saw.
For example: this one (4) concluded that heavy marijuana smoking decreased sperm motility and reduced sperm with normal morphology, but discarded a hormonal reason for that (that is, testosterone had no relationship with the phenomenon), the thing is that when they stopped smoking, the sperm effect reverted.
So maybe, if you want to have kids, you should put your joint to rest for good, but this is another different topic.
So, can we smoke whatever we want and keep our testosterone levels intact?
Well, chances are that yes, but better if we don't go so fast.
The crucial difference between casual use and heavy use of cannabis and testosterone
If you are a casual weed smoker you are probably in the clear. As showed in this study  casual smokers were within the normal range and the means did not differ significantly from those of 13 control subjects.
Frankly, they labeled you casual if you smoked at least weekly, with 5.1 joints per week). Frankly, I don't consider that very "casual", but ok.
Now, we enter another more dangerous territory, heavy cannabis usage.
The relationship between cortisol and cannabis
A research team, led by Dr. Syed Shakeel Raza Rizvi, found that smoking marijuana had a significant impact on levels of cortisol, that is, “the stress hormone”.
Now, if you have read something more in this web, you should now that chronically elevated levels of cortisol inhibit testosterone. You are stressed, your body is pumping cortisol to cope with that stress so it has note enough pregnenolone and other raw materials to produce the optimum levels of testosterone.
So the scientists in that study found that heavy marijuana smokers have significantly higher levels of cortisol than non-smokers. So, due to the relationship between testosterone and cortisol, maybe even heavy users have normal testosterone levels, but I don't see how they have optimal higher testosterone levels.
In fact, normal testosterone levels range so wildly that you can have 400 ng or 1000 ng and both numbers are considered "normal".
A big caveat here: causality.
As they said, the relationship between stress and cannabis is not clear. Maybe the elevated levels of cortisol are triggered by heavy use of cannabis, or maybe those subjects smoke more weed because they are more stressed anxious people in the beginning. And they self-medicate with cannabis.
Having said that, it's true that this study  shows an increase in cortisol that is dose-dependant of cannabis.
Bottom line, if you smoke a lot, you should quit your foot from the pedal.
The case for medical marijuana and testosterone
What if you live in a country or state that has medical marijuana?
Well, strains grown for medical purposes tend to have lower THC ratios than recreational cannabis (always looking to increase the THC percentage because life seems better if you are stoned).
So if you have a prescription of medical cannabis, it's true and you are not abusing, you are again in the clear, it won't have a substantial effect on your testosterone.
I could go on and on, but it would be boring fast, it seems that cannabis and testosterone have no such bad relationship as we thought.
There is contrary evidence to the famous Kolodny study and, in fact, it seems that the popular wisdom about testosterone levels being directly affected by marijuana is a myth if you are a casual user.
If you are a heavy user, you are hampering your efforts if you want to increase your testosterone, probably because of the cortisol-testosterone relationship, so ease your usage, please.
Another thing is sperm mobility, quality of erections or even erectile dysfunction. Here the confusion and the contradictory results are even greater.
For example, some studies say that cannabis users can develop early erectile problems through endothelial dysfunction (7), meanwhile, others saw nothing. I quote one of the most recent works dealing with this issue.
"Studies examining the effects of cannabis use on male sexual function have been limited in both quality and quantity. Most results of these studies are conflicting and contradictory. While some did outline the beneficial effects of cannabis in enhancing erectile function, others did not. However, recent animal and in vitro studies have identified potential links between cannabis and sexual health. It appears that cannabis may actually have peripheral antagonizing effects on erectile function by stimulating specific receptors in the cavernous tissue".
Antagonizing is not a good word, believe me.
My head hurts when dealing with this issue, I know yours too, in fact, I left this topic out of the testosterone book and the testosterone companion because I could not find a good clear response, but these are my conclusions after almost dying or pure boredom researching studies.
1) That cannabis directly lowers testosterone is a myth if you use it casually. The studies that showed the lowering effect were made with very heavy and very chronic users, and even in those circumstances there is contrary proof, so it's not a fact, but a myth.
2) That you won't optimize testosterone if you smoke a lot of cannabis.
3) That cannabis can have something to do with another issues of male sexual health, like sperm quality, motility or even Erectile dysfunction.
We are talking again about heavy usage and some effects were reverted after stopping consumption, but it's quite possible that it has something to do. So don't put your boners in danger, it's not a good place to live…
(1) Kolodny, R.C. et al, "Depression of Plasma Testosterone Levels After Chronic Intensive Marijuana Use," New England Journal of Medicine 290:872-74 (1974).
(2) Mendelson et al (1974)
(3) Normal Plasma Testosterone Concentrations after Marihuana Smoking. N Engl J Med 1975; 292:867-868April 17, 1975
(4) Hembree, W.C. et al, "Changes in Human Spermatozoa Associated with High Dose Marijuana Smoking," pp 429-39 in G.G. Nahas and W.D.M. Paton (eds), Marijuana: Biological Effects, Oxford: Pergamon Press (1979).
(5) Plasma Testosterone Levels in Healthy Male Marijuana Smokers. Paul Cushman
(6) The effects of cannabinoids on serum cortisol and prolactin in humans. Mohini Ranganathan, Gabriel Braley, Brian Pittman, Thomas Cooper, Edward Perry, John Krystal, and Deepak Cyril D’Souza
(7) Early endothelial dysfunction as a marker of vasculogenic erectile dysfunction in young habitual cannabis users. A Aversa, F Rossi, D Francomano, R Bruzziches, C Bertone, V Santiemma and G Spera.