I'm not sure I would say Marijuana is a completely safe and harmless drug. The effects of the use are a lot less drastic than with other drugs, but regular and heavy users, in particular if they are young, are known get sluggish to the point where it becomes a huge problem for them. Some also develop mental illnesses.
That is probably a lot less drastic than the effects of e.g. getting completely drunk every day. But one of the problems is that there is no public evidence based knowledge about the effects of drugs like Marijuana. People either believe it's completely harmless, or they think it's the devil. There is also no good social canon on the use of such drugs. Getting drunk every day has obvious social stigma in all circles, but smoking hash every day can be accepted behaviour in certain circles.
That is actually the nice thing about this study, they try to correct this and give facts.
That is probably a lot less drastic than the effects of e.g. getting completely drunk every day. But one of the problems is that there is no public evidence based knowledge about the effects of drugs like Marijuana. People either believe it's completely harmless, or they think it's the devil. There is also no good social canon on the use of such drugs. Getting drunk every day has obvious social stigma in all circles, but smoking hash every day can be accepted behaviour in certain circles.
That is actually the nice thing about this study, they try to correct this and give facts.