Depends on how you look at it. Marijuana deeply affects the nervous system, so if you smoke enough of it, you might suffer from numerous full-body disorders. Also, anything in large amounts is poisonous - even the oxygen we breathe. Marijuana can affect the liver, however, if the liver is so damaged that it can't "clean" your blood or it thinks nothing is wrong with it, then all of your organs can suffer long-term or even permanent damage. While alcohol may make some people so dependent on it that they live to drink and drink to live, those who smoke marijuana can be looking at much worse consequences.
Happiness is not about being perfect.
It is about seeing beyond the imperfections.