Yes, it CAN be mentally addicting if you have an addictive personality and/or don't keep yourself in check. I hate to say this DD, but it's unfair to take away something that could help MANY people just because you couldn't controll your "addiction" to it. I say this because I also used to be mentally addicted to the stuff, until I realized that 85% of life is mind over matter and am now able to recreationally enjoy it without going overboard. I'm happy with my choice, I would hate to not use it, I enjoy it, and yet I was tired of being down, out, "needing" it (note the quotes), and spending tons of money on it. So I literally stopped myself by constantly being disciplined and being mindful of my actions constantly, almost ritualistically, like a zen buddhist monk or something . I get better with it all the time, and with other things (i.e. losing weight, quitting coffee, meeting goals, keeping my house clean, etc).
I dunno, just my take on it...I've noticed pretty much anyone who is against medical marijuana is against it because of their own personal life experience (not anything based on science or reason), and that just doesn't seem very fair to everyone else.
I'm almost fully against western medicine...one pill of vicoden has far more poison in it than weed smoked a vaporizer, and vicoden is physically addicting, like crack or heroin...whereas weed is not addicting at all (unless you let it be).