Marijuana is psychologically addicting, not physically.
In other words, it all depends on the person. I, myself, am able to control myself. I haven't smoked in 1-2 weeks because I plan to wait and have a big session on the 31st. Smoking weed is so much better when you wait for the moment.
AIDS/HIV patients use medical marijuana to induce hunger. They normally stay with no appetite so they use weed to bring in the munchies.