While it does have some serious potential as a money make for the government if they were to put a serious tax on it, studies are coming out finally of the harmful effects. Not saying that alcohol or tobacco doesnt cause serious side effects with chronic use but the marijuana studies are finally becoming public. Myself, I have never touched the stuff but critical of those that think that there is nothing wrong with it. Roommates in college were smokers of it. The fact that they are seeing similar brain scans to those of schizophrenia is pretty drastic.
http://www.cnn.com/2013/12/16/health/time-marijuana-brain/
The article, which is a standard piece of sensationalist mainstream 'science' journalism, completely misinterprets almost to the point of lying the content of the study. What the study actually concluded was that "schizophrenia subjects demonstrated cannabis-related neuroanatomical differences that were consistent and exaggerated compared with cannabis-related differences found in controls", and further that "future longitudinal studies could help determine whether cannabis use contributes to these observed shape differences or whether they are biomarkers of a vulnerability to the effects of cannabis that predate its misuse".
Here's a link to the actual study. It's way less exciting than what the author of the article wrote of course, but if she didn't know how to lie through her teeth for readers then she wouldn't have a job.
http://schizophreniabulletin.oxfordjournals.org/content/early/2013/12/10/schbul.sbt176.abstract?sid=31a54672-cd55-4409-bba0-1010b40b5221On the subject of whether marijuana use actually puts you at risk for scizophrenia, here's a recent study from Harvard Medical School;
http://www.schres-journal.com/article/S0920-9964%2813%2900610-5/abstract"The results of the current study suggest that having an increased familial morbid risk for schizophrenia may be the underlying basis for schizophrenia in cannabis users and not cannabis use by itself."
The lesson here is that any science journalism from a mainstream news outlet is trash with almost no exception.
Beside that,
"smoking every day for about three years"
Ignoring that this is a fairly unreasonable amount of marijuana to be smoking, do you know what medical condition affects those who, say, drink every day for three years?
Death.