I have been warning young men for years about the dangers of developing abnormal breast tissue when they use marijuana. There are also things like OTC antacids like cimetidine, American ginseng supplements, and some prescription blood pressure medications that can cause it. On of the worst parts of the marijuana is that the estrogens that are made recirculate in the intestines and the liver so even one episode of smoking will cause the metabolites to be around for days as it will be excreted form the liver into the intestines and then reabsorbed and recirculated again.
So there you go, another reason not to partake of the weed. I perform many gynecomastia or male breast reduction surgeries every year, but I would prefer to perform it when uncontrollable causes have made it appear it if at all possible Below is a recent article for your review.