Unlike alcohol abuse and other drug abuse that kill the grey cells causing brain damage or long term memory loss, the use of Marijuana causes only short term memory loss and that too, only while the individual is under its influence. Marijuana does not cause long term memory loss neither does it effect the immune system in the body.
According to the UCLA School of Medicine study in 1997, (Volume 155 of the American Journal of Respiratory & Critical Care Medicine) on 243 Marijuana smokers for chronic lung disease, over the period eight years, it was found that "Neither the continuing nor the intermittent marijuana smokers exhibited any significantly different rates of decline in lung function as compared with those individuals who never smoked marijuana." In relation to smoking of Marijuana, the study found "No differences were noted between even quite heavy marijuana smoking and non-smoking of marijuana."The study concluded that unlike tobacco that is a major cause of deaths in the country, death from an overdose of Marijuana has never been recorded so far.
Moreover, Legal prohibition of drugs is not going to prevent its consumers from taking them.