It's super easy for anyone who knows how to use PubMed or search scholarly journal articles. Here are some peer reviewed materials from reputable scientific journals I found in about six minutes. It's very common knowledge among most people that there are risks associated with MJ use. (I don't think it should be illegal, by the way, but I do think all risks need to be discussed, just like cigarettes and alcohol) Ok: Carcinogens presence: http://www.ncbi.nlm.nih.gov/m/pubmed/12412839/ ( read the abstract) Estrogen-like activity: http://www.ncbi.nlm.nih.gov/m/pubmed/6296360/ (This is why it shrinks testicles and causes gynecomastia) Physiological brain changes in marijuana users: http://www.ncbi.nlm.nih.gov/m/pubmed/10772599/ (it shrinks your brain... Surprise!!) Psychological events related to cannabis use: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2424288/#!po=0.980392