Countless rumours have been circulated regarding the potential effects of cannabis for as long as humans have consumed the plant. From perceived medicinal benefits to health risks, we’ve heard it all. In many cases, there is little evidence to support these claims – whether they are positive or negative. Common examples include the much-quoted belief that cannabis can cure cancer, lower sperm count, and reduce levels of testosterone.
Cannabis has topped the chart of most-used illegal drugs in the UK since estimations began in 1995. In this time, young males have also been the top demographic to use recreational cannabis. According to Statistics Canada, 21% of males reported using cannabis in the last three months, compared to 19% of women in 2020 – one of the smallest gaps seen in recent years.
There have been a number of reports in recent years that THC can negatively affect the production of testosterone in the human body. If this is true, then the rising levels of THC found in illicit cannabis products are potentially an area for concern. But is this true? And if so, how does cannabis use actually lower testosterone levels?
What is testosterone?
Our bodies naturally produce a mind-boggling number of chemicals, each with its own unique role in cognitive, physiological, and immune functions – and much more! Hormones, including testosterone, are extremely important in a huge number of processes. For example, testosterone is a major sex hormone – particularly in males – that plays a number of important roles, including the development of the penis and testes, muscle strength, bone growth, and sperm production.
Levels of testosterone typically increase when a male starts puberty. In fact, testosterone is associated with many qualities associated with puberty, including the deepening of the voice and the appearance of facial and pubic hair (although it may actually play a role in balding as we get older!).
Testosterone is often associated with “masculine” development and characteristics such as aggression. However, the role of testosterone in these stereotypically “macho man” personality traits is largely a myth. While adolescent males with lower levels may not experience typical masculinisation, this hormone doesn’t belong exclusively to the male sex.
Testosterone is one of several androgens (male sex hormones) that are also produced in females. In females, it is produced in the ovaries and adrenal glands and plays an important role in ovarian function, bone strength, and sexual behaviour.
Cannabis and testosterone
Several studies have suggested that there may be a link between cannabis use, lowered testosterone levels, and even infertility in males. For example, one 1974 study concluded that “chronic intensive use of marihuana may produce alterations in male reproductive physiology through central action” and plasma testosterone was reportedly lower in frequent cannabis users.
Similar findings were reported in a 1983 review that stated: “A reanalysis of existing data established that testosterone levels are depressed both after smoking one marijuana cigarette and after intravenous infusion of delta-9-tetrahydrocannabinol.” A more recent study likewise concluded that chronic marijuana use was associated with a significant dose-dependent decrease in total testosterone levels – but the study was carried out using macaques, not human participants.
Furthermore, other studies have contradicted these conclusions. Particularly notable are the findings of two studies that indicated THC use was actually associated with an increase in testosterone. One of the studies, carried out by researchers from the National Cancer Institute, Maryland, USA, and published in 2017 concluded that serum testosterone concentrations were higher in men with more recent cannabis use. Another review reported that cannabis use did not influence serum testosterone levels in infertile men, but noted the contradictory nature of the existing literature.
So, this is confusing – right? Does cannabis lower testosterone levels or doesn’t it? Will we ever know? Well, right now, the evidence simply appears to be inconclusive. As we consistently see with almost everything related to cannabis, there is still a critical lack of research that continues to fuel potentially dangerous misinformation.
In the absence of any solid conclusion with regard to the association between cannabis and changes in testosterone levels, the best advice remains to consume cannabis – and any other recreational drug –with caution and care.