You've heard the rumor: men who consume too much cannabis are bound to develop gynecomastia. You know, “moobs.”
Also known as “man boobs,” gynecomastia is the abnormal growth of breast tissue (not fat) in men that is generally attributed to an imbalance of hormones; namely an excess of estrogen and lowered levels of testosterone. The myth that cannabis causes gynecomastia has been around for years, even reported as news in 2013 by CNN based on claims made by a plastic surgeon who relied on a 2002 study noting a “plausible” link between the plant and the condition. But is there any truth to all this hype?
Admittedly, science on the subject is scarce, and much of the research done on the relationship between cannabis and gynecomastia is decades old. However, more findings have refuted the claim that using heavy amounts of marijuana causes gynecomastia than back it up. We can look as far back to the November 1977 issue of The American Journal of Surgery, which published a study that states “evidence does not support the previously reported relationship between chronic cannabis use and gynecomastia."
Basically, we don't have clear evidence showing that cannabis use increases estrogen levels in men. In February of 1983 The Journal of Pharmacology and Experimental Therapeutics published a study that found: “although estrogen receptor binding activity was observed in crude marijuana extract, marijuana smoke condensate, and several known components of cannabis, direct estrogenic activity of cannabis extract could not be demonstrated.” Also, while there have been claims that cannabis use can lead to temporarily low testosterone levels, a study published in the August 1991 issue of Drug and Alcohol Dependence concluded that “chronic marijuana use showed no significant effect on hormone concentrations in either men or women.”
To this day the National Institute of Health and the Mayo Clinic list marijuana as a possible cause for gynecomastia, despite the fact there isn't any solid science to back this up. It is entirely possible that consuming cannabis does impact the hormones of men (and women) in some way, but we need more research to better understand how marijuana affects our hormone levels and find out once and for all if it has any impact on someone developing “man boobs.”