Does cannabis lower testosterone? What the UNIGE-SCAHT study measured

In a study by the University of Geneva (UNIGE) and the Swiss Centre for Applied Human Toxicology (SCAHT), 47 young men who used cannabis had higher testosterone than 47 controls, by about 23% according to UNIGE. Two other androgens made by the testicles were also higher, but not those from the adrenal glands. This is a cross-sectional study, which shows an association and not a cause, carried out with cannabis containing THC and not with CBD products. Semen was not analysed: it says nothing about fertility. To read this study in context, see also our guide how to read a scientific study on CBD.

A question debated for fifty years

According to the World Health Organization, some 150 million people use cannabis worldwide. Its effect on male hormones has long been debated. THC, its main psychoactive molecule, binds to the CB1 and CB2 receptors of the endocannabinoid system, which are found all along the axis linking the brain to the testicles, and in the testicles themselves.

Published results are often described as contradictory. The only study to report lower testosterone in cannabis users dates from 1974 and involved 20 users and 20 controls. More recent studies in Denmark and the United States, covering thousands of young men, instead measured higher testosterone in users, but based on self-reported use, without a blood test.

In 2024, an earlier study of the same Swiss cohort (Zufferey et al., journal Andrology) had found higher levels of androgens, the so-called male hormones, as well as oestradiol and SHBG, a protein that carries sex hormones, in users. The differences were more marked in chronic and recent users and in those whose cannabis also contained CBD. The new work measures dozens of hormones at once.

94 young Swiss men from military recruitment

Participants were recruited across Switzerland between 2005 and 2017 during compulsory military recruitment, which makes it possible to reach the general population. They were 18 to 23 years old when sampled: 47 cannabis users and 47 matched controls.

Use was not only self-reported. Users had said they had taken cannabis in the previous 7 days, and their blood contained THC and THC-COOH, a breakdown product of THC. According to the authors, these samples reflect very recent use, within the previous 12 hours. Controls reported no use and had no detectable THC or THC-COOH. The study therefore concerns cannabis containing THC, used recreationally, and not CBD products.

Using a highly sensitive analytical technique, mass spectrometry, the team looked for 171 steroid hormones in the blood, the family that includes testosterone, cortisol and progesterone. In total, 70 were reliably identified. Time of sampling, body mass index and tobacco smoking did not explain the differences.

Higher androgens of testicular origin

The three main androgens produced by the testicles were significantly higher in users: androstenedione, a precursor of testosterone, testosterone itself and dihydrotestosterone (DHT), the most potent androgen in men. According to the UNIGE press release of 28 May 2026, testosterone was about 23% higher in users. A step in the same production pathway, 17α-hydroxyprogesterone, was also slightly higher.

Other hormones did not differ between the two groups: progesterone, cortisol, cortisone and 11-deoxycortisol. Among users, testicular androgens were higher the higher their blood levels of THC and THC-COOH.

This result is in line with the large Danish and American studies. In the Danish study of 1,215 young men, testosterone was 7% higher in cannabis users after accounting for other factors.

The testicles rather than the adrenal glands

In men, part of the androgens is made by the adrenal glands, which sit above the kidneys. This is the case for the so-called 11-oxy androgens, including 11-ketotestosterone, whose activity is comparable to that of DHT. These androgens were at similar levels in users and controls. Only those of testicular origin were therefore higher.

LH and FSH, the pituitary hormones that control the testicles, did not differ either. For the authors, the most likely hypothesis is a direct effect of plant cannabinoids on Leydig cells, which produce testosterone and carry CB1 receptors. “Cannabis would thus have a direct action on the testicles”, sums up Serge Rudaz, the study’s corresponding author at the University of Geneva.

The mechanism remains uncertain: LH and FSH are released in pulses, and a single blood sample captures them poorly. A role for the liver is not ruled out, although the authors consider it secondary.

Two progesterone derivatives linked to exposure

The clearest differences concern two progesterone derivatives: 11β-hydroxyprogesterone (11β-OHP4) and 5β-dihydroprogesterone (5β-DHP4). Both were markedly higher in users, with statistically very strong differences.

The researchers then separated chronic and occasional users according to their blood THC-COOH level, with a threshold of 40 µg/L. 11β-OHP4 did not differ significantly between these two subgroups: it would signal exposure to cannabis in general. 5β-DHP4 was higher in chronic users and rose with THC and THC-COOH levels: it would also reflect the intensity of use. Testosterone, for its part, did not differ between chronic and occasional users.

The role of 5β-DHP4 in male reproduction remains unknown. Progesterone is, however, involved in how sperm cells function, which according to the authors justifies further research.

What the study shows and does not show

What the study shows: in 47 young men who had recently used cannabis containing THC, several androgens of testicular origin were higher than in 47 controls, while adrenal androgens did not vary. Two progesterone derivatives emerge as possible markers of cannabis exposure.

What it does not show: it is a cross-sectional study, a snapshot at one point in time. It establishes an association, not cause and effect. Reverse causality is possible: men with naturally higher testosterone could be more inclined to take risks, including using cannabis. The increase could also be a compensatory response, if the body becomes less sensitive to androgens in the presence of cannabinoids. Diet, alcohol, sleep or stress could not be taken into account.

The study says nothing about fertility: semen was not analysed. UNIGE stresses that higher testosterone is not a sign of better semen quality, as the link between testosterone and fertility is very complex. Available data are inconclusive: the 2024 study found no significant difference in semen parameters, whereas the Danish study reported fewer sperm cells in users.

Finally, the results concern short-term effects in recent, young, Swiss users. According to the authors, they cannot be extended to women, other age groups or former users, and a risk of false positives remains.

And in Switzerland?

The cohort comes from Swiss military recruitment, and the study was carried out and funded in Switzerland. It concerns cannabis containing THC, used recreationally, and not the CBD products sold freely in Switzerland. These products contain less than 1% total THC (see what the 1% threshold measures), fall under other laws and are not medicines.

Hemp and products with 1% total THC or more are narcotics, and their non-medical use is prohibited. In the 2024 study of the same cohort, the CBD in question was present in the cannabis used, alongside THC; its abstract does not make it possible to isolate an effect specific to CBD. The detailed framework is set out in our guide to Swiss legislation, and our feature on hemp cannabinoids places THC and CBD among the plant’s molecules.

In summary

In 47 young Swiss men who had recently used cannabis containing THC, testosterone and two other androgens of testicular origin were higher than in 47 controls. Adrenal androgens did not vary, which points the authors towards a direct effect on the testicles. This cross-sectional study shows an association, not a cause, does not measure fertility and does not concern CBD products.

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